7. Running the Modules Individually

7.1  Introduction  

Each module can be run individually using the batch files created by FIXDRV, edited if necessary to change input controls.  To run the modules from a batch file, use the operating system option for the redirection of standard input devices.  This option allows the user to redirect the input from a batch file rather than from the keyboard.  For example, to run MODEL from batch input file bvent7.002, type   

	model <bvent7.002 

and the program will take responses from the input file.  This is the basis of the batch mode of processing.  An examination of the primary and secondary input files output by FIXDRV will make these concepts clearer (Section 5.3). 

7.2  Running ARC 

The function of ARC is to create a T-file of tabulated ephemerides of the satellite coordinates and the partial derivatives of these coordinates with respect to initial conditions and the other adjustable parameters (just the three non-gravitational force parameters in the current version).  Below is a sample batch file from the example network discussed in Chapter 5: 

File bvent7.001  (ARC)
PRN  3
PRN  6
PRN  9
PRN 11
PRN 12
PRN 13
END
IGS92 SPHRC  900.0   75.0  GPST  INERTIAL   B1950 
arcout.002
gvent7.002

  87  23 21 37 23.00000
  87   9 16 37 23.00000
Y
tvent7.002

The first five lines list the "names" of the satellites to be integrated (ARC expects names of the form PRN  nn or NAVSTAR nn), terminated by END.  The next line specifies the models and integration controls, read under format control.  The preferred gravitational model is IGS92, invoking the IGS standard for GM and an 8x8 truncation of the GEM-T3 gravity field.  However, most GAMIT analyses prior to release 9.25, including the GARNER orbits generated at SIO, have used MERIT standards, so if you are reintegrating a G-file for regional analysis but combining the H-files with those generated elsewhere, be careful that the gravitational models are consistent.  In multiyear anlysis for station positions and velocities, there is no serious problem in having used different gravitational models to generate the orbits since the adjustments of initial conditions will absorb most of the model differences.  

The only radiation pressure model available in the past has been a "flat-plate" or "spherical" (SPHRC) model in which adjustable parameters were defined for the Sun direction ("direct"), spacecraft y-axis ("y-bias"), and the Earth-pointing (spacecraft z) axis ("z-bias).  Only the first two of these are well determined and usually estimated.  A better geometric model is defined by the Sun-pointing axis, y-axis, and a third axis orthogonal to both of these.  Investigators at AIUB (Berne) (Beutler et al., [1994]; see references in Chapter 2)  have termed this third axis "x", but we designate it the "b-axis" to distinguish it from the spacecraft x-axis.  This parameterization is available by specifying SRDYB, which allows three adjustable parameters, or BERNE, which allows the three constants plus once-per-rev accelerations (sine and cosine terms) along each of these three axes, for a total of 9 parameters.  Beutler et al. [1994] (and the AIUB standard processing) incorporate into these formulations the ROCK4 model described by Fliegel et al. [J.Geophys. Res., 97, 559–568, 1992], modified to lump the "X" and "Z" forces into a single "direct" force (M. Rothacher, personal communication, 1994).  Tests carried out at MIT thus far have shown no improvement (in fact, a slight degradation) using the ROCK4 model, so we do not include it in BERNE or SRDYB.  A second difference between the GAMIT and Bernese formulations is that we include shadowing only in the constant, direct solar term, whereas Berne includes it for all 9 terms.  Two additional parameterizations are available:  SRDYZ uses the same adjustable parameters as SPHRC but includes the original formulation of the ROCK4 model, with the additional forces applied along the X and Z axes.  Finally, SRXYZ uses adjustable parameters and ROCK4 forces along the spacecraft x, y, and z axes.  The details of these formulations may be found in the code and documentation of subroutine ertorb.f in the /arc directory. 

The next two entries on the same line are for the T-file tabular interval and integration step-size, both given in seconds.  The nominal values are 900 (15 minutes) and 75 seconds, respectively.  The tabular interval must be an even multiple of the integration step-size.  The final three entries give the time type (GPST or UTC) desired for the T-file (GPST is now default), and the reference frame, which in the current version must be 1950.0 inertial.  

The next two lines give the filenames of the ARC printed output and the input G-file containing the initial conditions and initial values of the non-gravitational force parameters.  There is then a blank line (for historical reasons), followed by the start and stop times of the integration, given as (2-digit) year, day-of-year, hours, minutes, seconds.  The times given are the times between which interpolation can occur; the actual values on the T-file will extend five epochs beyond the limits given.  The last two lines of the ARC input contain a single control ( Y or N )indicating whether the variational equations (partial derivatives with respect to initial conditions and parameters) are to be integrated, and the name of the output T-file. 

The ARC print output file (ARCOUT.ddd ) summarizes the input controls and also records the times when each satellite is being eclipsed by the Earth.  This information is useful in evaluating the level of stochastic variation (Markov parameters) to be allowed with multisession T-files in GLOBK.  A sample output file is given below but with the summary for only one satellite included:

Output archive file: arcout.278      
 Input ICs file: ggpst7.278      

 9.16 of 94/07/26 14:40:00 (SunOS)       

 Standard spherical radiation pressure model used

 Epoch of ICs, read from: ggpst7.278      
 Yr Mn Dy    Hr  Min Sec  JD    Sec of Day (GPST)
 87 10  5    18 22 59.  2447074 66179.00000000

 Input start time for observations: 
 Yr Mn Dy    Hr  Min Sec  JD    Sec of Day (GPST)
 87 10  5    13  7 59.  2447074 47279.00000000

 Input stop time for observations: 
 Yr Mn Dy    Hr  Min Sec  JD    Sec of Day (GPST)
 87 10  5    23 37 59.  2447074 85079.00000000

 TDT-GPST at IC epoch   = 51.1840 sec

******************************* PRN  9 **********************************
 PRN  9 is a block 1 satellite and has a mass of  462600.0 grams

 ICs found in the g-file:  X    Y    Z    XDOT YDOT ZDOT RAD1 RAD2 RAD3

 Satellite and ICs: PRN  9          
 -0.256749494345660D+05  0.415313921343370D+04  0.565073203730440D+04
 -0.104843035787760D+01 -0.158739652566680D+01 -0.336546540194340D+01
  0.100000000000000D+01  0.000000000000000D+00  0.000000000000000D+00

 Sat   Se  mimjr Ax  Eccen'ty   Perigee      Inclin'n    Ascen.Node   Mn Anomaly   
         ___KM.___             DDD MM SS.S  DDD MM SS.S  DDD MM SS.S  DDD MM SS.S  
 PRN  9  26560.651   0.012882   66 23 29.5   63 59 40.5  356 53 45.0   98 29 17.0

 PRN  9 Radiation pressure, Y-Bias, Z-Bias:  0.100000D+01  0.000000D+00  0.000000D+00

 IERS92/IGS Standards for model constants

 Times written to T-file header  (GPST)
 IC epoch:    87 10  5 18 22 59.000000
 Start   :  1987 10  5 11 22 59.000000
 Stop    :  1987 10  6  1 22 59.000000
 No. epochs:   57
 Tabular interval:   900.0  Integration interval:  75.0000

                      PJD      LAMBDA  YR DOY  MO  DY  HR MIN PRN
 Start eclipse:  2447074.56631  0.161  87 278  10   5  13  35 PRN  9
 Eclipsing:      2447074.54027  0.010  87 278  10   5  12  57 PRN  9
 Eclipsing:      2447074.53940  0.912  87 278  10   5  12  56 PRN  9
 End eclipse:    2447074.53853  1.000  87 278  10   5  12  55 PRN  9

 Start eclipse:  2447075.03940  0.432  87 279  10   6   0  56 PRN  9

 Output yaw file:  yvent7.278
 Output ephemeris file: tvent7.278      

The identification of the satellite as "Block 1" or "Block 2" is relevant to select the nominal direct acceleration in the radiation-pressure models.  These are further modified by the nominal mass of the satellite, read from file svnav.dat.  This nominal direct acceleration also becomes the unit for the (smaller) estimated accelerations along the x-, y-, z-, and b-axes.

For the eclipse summary, the first line printed ( Start eclipse ) gives the first integration epoch for which the shawdow factor ( LAMBDA; 1.0 = full sunlight ) is less than 1.0; this is followed by all epochs for which the factor is less than 1.0 (only one in this case) and the first epoch for which the factor is again 1.0 ( End eclipse ). 

During the integration ARC will combine the eclipse information with the history of spacecraft yaw biases given in svnav.dat to create a session-specific Y-file of predicted spacecraft attitude for the span covered by the T-file.  An example of a Y-file a span in late 1995 is shown below:

PRN  YAW_RAT BIAS YR MO DA  HR MN ECLIPSE                            
  39 NOMINAL yaw rates      - explanation of file in read_yaw.f                 
  1   0.123  P    95 10 30   9 15                                               
  2   0.113  N    95 10 30   9 15                                               
 ...
  9   0.128  P    95 10 30   9 15                                               
  9   0.128  P    95 10 30   9 37  E                                            
  9   0.128  P    95 10 30  15 37                                               
  9   0.128  P    95 10 30  21 36  E    -134.4    9.7                           
  9   0.128  P    95 10 31   3 36                                               
 12   0.199  U    95 10 30   9 15                                               
 ...
 31   0.097  P    95 10 30   9 15                                               

Examples are given for satellites with positively-biased ( P ), negatively-biased ( N ), and unbiased ( U ) yaw, and for satellites with no eclipses (PRNs 1, 2, 12, and 31) and two eclipses and a noon maneuver during the span (PRN 9).  The extra values given for the second eclipse of PRN 9 are the yaw and beta angles at the start of the eclipse; these are not written into the original Y-file by ARC but rather added by MODEL during processing.  For an explanation of the history and importance of yaw modeling see Secton 2.3 and Bar-Sever [1996].  See Section 9.8 for a listing of svnav.dat giving the history of yaw biases for all of the GPS satellites. 

7.3  Running MODEL 

The function of MODEL is to create a C-file containing the observation residuals (O-Cs) and partial derivatives to be used in SOLVE to estimate adjustments to parameters.  Below is a sample batch file from the example network discussed in Chapter 5:

File bvent7.002  (MODEL)
O		Old X-file format
pvent7.002	Print file
ivent7.002	Station clock polynomial (I-) file
lvent7.002	Coordinate (L-) file
xcato7.002	Input X or C file
ccato7.002	Output C-file
N		Delete input C-file?
tvent7.023	T-file
I		Inertial frame
N		Use W-file?
N		Use Z-file?
jvent7.002	Satellite clock polynomial (J-) file
0  1  3	Geodetic datum / Tide model / SP Earth rotation
15.0 NONE	Elevation angle cutoff / Antenna model
2		Clock model
1013. 25  20.0  50.0	Pressure, temp, humidity
SAAS  SAAS  CFA  CFA	

The first line indicates the type of experiment—static (S), kinematic (K), or dynamic (D)—and is used to guide MODEL in the reading of the X-file.  There is an additional key-letter input possible ('O') if the X-file is 'old-style', written prior to October, 1991, and doesn't itself have an identifier for the type of experiment.  (This option is actually the one used in our 1987 example.)  The "hooks" for kinematic and dynamic processing have been put in MODEL (and most of the other modules), but these features are not yet operational.

The second line gives the name of the print (P) file that records the file-header and model information for the run.  The P-file name is normally the same as the X-file name except for the first character, but any name can be used for test purposes.

The third line gives the name of the receiver-clock (I) file, which should have been created by FIXDRV.  The I-file name is normally the same as the D-file name except for the first character, but again is arbitrary.

The fourth line gives the name of the site-coordinate (L) file.  The L-file name is normally the same as the D-file name except for the first character, but again is arbitrary.

The fifth line gives the name of the input X- or C-file.  MODEL will use the first character to determine the file type.  The sixth line gives the output C-file name.  This is followed by an input ('Y' or 'N') indicating whether the input C-file should be deleted at the end of the MODEL run.  If the the input data file is an X-file, MODEL will not delete it regardless of the entry on the seventh line. 

The eighth line gives the name of the satellite ephemeris (T) file.  The T-file name is arbitrary except for the first character.  For single-day T-files, use of the last digit of the year and the day of year are convenient.  

The ninth line indicates whether the MODEL computations are to be performed in an earth-fixed ('E') or inertial ('I') coordinate system.  Only the inertial computations have been adequately checked to be used in serious analysis; also, the present version of ARC requires that the T-file be in the inertial system defined by the equator and equinox of 1950.0. 

The next group of questions tell MODEL whether you wish to use an input table for surface meteorological data (W-file) or water-vapor-radiometry data (Z-file).  If the response to either of these questions is "Y",  the name of the file should be added as an additional line following the question response.  Use of these tables is relatively untested. 

The next line gives the name of the satellite clock (J) file.  The name is arbitrary but is usually the same as the D-file except for the first letter.  The J-file should have been created from an E-file using MAKEJ.  With Selective Availability invoked, a large J-file, computed using observations at a site with an atomic frequency standard, may be necessary.  

Line 13 has three integers designating the geodetic datum and the models to be used for solid-earth and ocean tides and short-period (diurnal and semidiurnal) oscillations of UT1 and pole.  The current version of GAMIT works properly only in spherical (internally Cartesian) coordinates, so '0' should always be specified for the datum.  The integer controlling the tide model is binary coded—the first (1) bit for the default frequency-independent model for solid-earth tides, the second (2) bit for a frequency-dependent model for the K1 solid-earth tide,the third (4) bit for the pole tide, and the fourth (8) bit for ocean tides.  The default is for the frequency-dependent model only, to be consistent with previous releases of GAMIT, but the first three models have been moderately tested.  Application  of ocean tides requires an additional input table (otide.) and is still being tested

Line 14 gives the elevation cutoff angle (15 degrees in the example) and a keyword indicating the model to be used for antenna phase-center variations.  The default is NONE, but a table (antmod.dat) may be used to provide an elevation-dependent (ELEV) or elevation-and-azimuth-dependent (AZEL) model.  See Appendix 7 for the current state-of-knowledge of the mean and time-variable locations of the L1 and L2 phase centers for commonly used GPS antenna. 

The next lines specifies the way in which the receiver clock is determined.  A value of 1 indicates no correction is to be calculated—the time-tag on the X- (or C-) file is accepted as correct; this option is used for a receiver that keeps its clock synchronized with GPS time.  A value of 2 indicates that the first or second order polynomial estimated from pseudoranges in FIXDRV and stored in the I-file is used to model the clock throughout the session; this option is valid for clocks that maintain continuity and have a stability of better than 1 part in 108 over the session, such as the TI4100 or any receiver attached to an atomic frequency standard.   A value of 3 forces a clock estimate from pseudoranges at each epoch; this is the most general option and can be used under all circumstances except when the clock is synchronized but the pseudoranges are corrupted, as was the case with early MiniMac data. 

The last two lines allow you to select the default (fixed) values for surface meteorological data and the models to be used in computing the atmospheric delays.  The default models are shown; see Chapter 8 for a more detailed discussion.

A summary of the MODEL run is contained in the P-file.  A typical P-file is shown below.  It records, successively in divided sections, 1) the version and files used, 2) the X-file header information, 3) T-file header information, and 4) the information actually used by MODEL and recorded on the output C-file header.  In reading a P-file, be careful not to confuse X-file header values (for, e.g. antenna height or station coordinates) with the values read at run-time and used by MODEL.  At the end of the P-file are warnings issued by MODEL regarding the calculation of receiver-clock corrections.

----------------------------------------------------
 ** MODEL VERSION AND INPUT FILES SUMMARY **

          Program MODEL Version 9.23 of 93/12/23 14:35:00 (apollo)
 MODEL Run on 1993/ 12/ 27   8:53:59 by rwk             
 Receiver-clock (I-) File :   ivent7.278      
 Site Coordinate (L-file) File :   lvent7.278      
 Input Observation File: xcatod.278      
 Output C-file         : ccatod.278      
 Ephemeris (T-) File :   tvent7.278      
 SV clock (J-) File :    jvent7.278      
----------------------------------------------------
 ** X-FILE HEADER INFORMATION **

GPS Phase and Pseudorange for GAMIT Processing                                  
                                                                                
 MAKEX v. 6.31 of 89/08/18 20:47:                                               
 Run by brad             on 1989-08-23 14:21:23                                 

 MADE FROM FILE: //bullen/data/gps/trex9/y87d278/cato7.278.fic                  
 HEADER FROM SOURCE FICA FILE:                                                  
 UNPACK  1.7     MIT GPS 1988021413:52:03   cato7kurt      MEMTEC               
 Operator input site code            CATO                                       
 Operator initials                   FW                                         
 Operator input receiver serial num  UN02                                       
 Operator input antenna height (m)       1.000000                               
 Operator input humidity                      75.0000                           
 Operator input temperature (deg C)          150.0000                           
 Operator input pressure (Mb)                980.0000                           
 Software version number                       1.2000                           
                                                                                
                                                                       CVIEW run
                                                                       CVIEW run
 X-File written from C-File :  ccatoc.278      25- 8-198912:25: 6        
                                                                                
END                                                                             

 Site: Solstice Cyn
 Coordinates (lat,lon,rad):  33 54 26.00037 118 47  4.928786372399.996000
 Receiver software:        0.00  Antenna:      
 Antenna offsets (Up North East) L1: 1.3410 0.0000 0.0000  L2: 1.3160 0.0000 0.0000  meters
 Start time: 1987 10  5   14 37 55.080

 Channels= 7   Epochs=  225   Interval= 120

 Original data interval=   0   Session= 1

 Partials= 0   IDUAL=               FRQFAC=            

 Satellite PRN=  3  6  8  9 11 12 13
 Lambdas      = -1 -1 -1 -1 -1 -1 -1
 Lambdas      = -1 -1 -1 -1 -1 -1 -1
 Lambdas      =  1  1  1  1  1  1  1
 Lambdas      =  1  1  1  1  1  1  1

---------------------------------------------------
 ** T-FILE HEADER INFORMATION **

  Tabular ephemeris file generated from gvent7.278       22- 3-1993 12:47:59    9

   10    5   87 18. 22. 55.000  Epoch of initial conditions
   10    5 1987  6. 45. 25.000  Ephemeris start
   10    6 1987  5. 37. 55.000  Ephemeris end
  1350.000  Tabular interval (sec) ;      62 T-file epochs
                                                                                 
  Satellite      PRN #         X            Y            Z           (km)
                          XDOT         YDOT         ZDOT         (km/s)
 PRN  3            3  -13976.90947  22548.10115   3693.22105
                      -1.197022016 -1.332068683  3.398577085
                      1.0000000000 0.0000000000 0.0000000000
 PRN  6            6  -24301.94729  -3636.94164 -10053.29647
                       1.533179434 -1.614024306 -3.172431699
                      1.0000000000 0.0000000000 0.0000000000
 PRN  8            8    2670.86604 -21097.41556  16134.95670
                       2.382239628 -1.649186958 -2.542288912
                      1.0000000000 0.0000000000 0.0000000000
 PRN  9            9  -25674.94943   4153.13921   5650.73204
                      -1.048430358 -1.587396526 -3.365465402
                      1.0000000000 0.0000000000 0.0000000000
 PRN 11           11   -8123.78727  -9883.81092  23389.41439
                       2.090429667 -3.175191854 -0.665730892
                      1.0000000000 0.0000000000 0.0000000000
 PRN 12           12  -14938.58513  10564.06675  19579.41385
                      -3.183528061 -0.822019884 -1.982415692
                      1.0000000000 0.0000000000 0.0000000000
 PRN 13           13  -15948.84045   9398.65578  19029.83793
                       0.520501497 -3.247050999  2.050852343
                      1.0000000000 0.0000000000 0.0000000000

 Satellites (PRN #) in channels selected:    3  6  8  9 11 12 13

---------------------------------------------------
 ** INPUT MODELING INFORMATION **

 Input I-file clock ploynomial coefficients 
 Epoch  (seconds)             0.117102E-04
 Rate  (seconds/second)      -0.420373E-08
 Acceleration  (1/SEC)        0.000000E+00
 Cubic term    (1/S/S)        0.000000E+00
 
Datum read from file GDETIC.DAT
 Title reads:  Geodetic Datums                                  yb/rwk  87.4.21       
 Datum selected:      a       1/f            DX    DY    DZ
 WGS84        6378137.000 298.257222101    0.000    0.000    0.000

Tidal corrections applied are: 1
The value is decoded as:
                      1 = solid earth tides
                      2 = frequency dependant K1 model
                      4 = pole tide
                      8 = ocean tides
The corrections are applied as per the binary option
That is a value of 15 implies all corrections

Short period earth orientation corrections applied are: 3
The value is decoded as:
                      0 = no short period corrections
                      1 = short period pole corrections
                      2 = short period ut1 corrections
The corrections are applied as per the binary option
That is a value of 3 implies all corrections

Elevation angle cutoff is: 15.00
Antenna phase centre model is: NONE
Antenna model choices are:
                    NONE=No Corrections Applied
                    ELEV=Elevation dependant model
                    AZEL=Elevation and Azimuth model

Constants for atmospheric modeling
 Sea-level pressure =           1013.250 mb
 Sea-level temperature=           20.0 degs C
 Relative humidity =               0.50 (fractional)

 Atmospheric propagation delay models:
  DRYZEN WETZEN DRYMAP WETMAP
   SAAS   SAAS   CFA    CFA   

---------------------------------------------------
 ** OUTPUT C-FILE HEADER INFORMATION **

GPS Phase and Pseudorange for GAMIT Processing                                  
                                                                                
 MAKEX v. 6.31 of 89/08/18 20:47:                                               
 Run by brad             on 1989-08-23 14:21:23                                 

 MADE FROM FILE: //bullen/data/gps/trex9/y87d278/cato7.278.fic                  
 HEADER FROM SOURCE FICA FILE:                                                  
 UNPACK  1.7     MIT GPS 1988021413:52:03   cato7kurt      MEMTEC               
 Operator input site code            CATO                                       
 Operator initials                   FW                                         
 Operator input receiver serial num  UN02                                       
 Operator input antenna height (m)       1.000000                               
 Operator input humidity                      75.0000                           
 Operator input temperature (deg C)          150.0000                           
 Operator input pressure (Mb)                980.0000                           
 Software version number                       1.2000                           
                                                                                
                                                                       CVIEW run
                                                                       CVIEW run
 X-File written from C-File :  ccatoc.278      25- 8-198912:25: 6        
                                                                                
Model 9.23 of 93/12/23 14:35:00 (apollo)                                        
 Run on 1993/12/ 27  8:53    by rwk                                             

   Record 2 :
 Site: Solstice Cyn
 Rcvr, SW:      0.00
 Coordinates (lat,lon,rad):  0.59179633 -2.07320273 radians   6372.284511
 Antenna offsets (Up North East) L1: 1.341 0.000 0.000  L2: 1.316 0.000 0.000  meters

 SKD=S   MTIME= 1   NEPOCH= 225   INTER= 120
 IRCINT=   
 Start time:   87  5 10   14 37 55.080  Session: 1

 NCHAN= 7   NDAT= 4
 DATTYP=   1   2   3   4
 PRN Numbers:    3   6   8   9  11  12  13
 LAMBDA:        -1  -1  -1  -1  -1  -1  -1
 LAMBDA:        -1  -1  -1  -1  -1  -1  -1
 LAMBDA:         1   1   1   1   1   1   1
 LAMBDA:         1   1   1   1   1   1   1

 Raw data file: XCATOD.278        T-file: TVENT7.278      

   J-file: jvent7.278      
   Bias flags (   1) :    0   0
   Ephemeris epoch (PEP JD, sec) :  2447074   66175.000
   Earth rotation

     Epoch (PEP JD, sec  )      : 2447074   66115.080
     UT1-TAI, UT1dot (s, s/d)   : -23.49007  -0.00166  UT1 type: 2
     xp,  xpdot (arcs, arcs/d)  :  -0.05586  -0.00060
     yp,  ypdot (arcs, arcs/d)  :   0.30169   0.00134
     psi, psidot (arcs, arcs/d) :  -0.99368   0.00000
     eps, epsdot (arcs, arcs/d) :   9.73222   0.00000

     Met data (series binary flag) :  7

     Station weight =   1.0
     NPART=15   NLABEL=20   NEXTRA 1
     EXTRA=.0000

   Record 3 :

     RLABEL, ISLOT, IDMS =SITE # LAT. (DMS)       1  1
                          SITE # LONG.(DMS)      11  1
                          SITE # ELL.HGT(KM)     21  0
                          ATMOSPHERE             31  0
                          SITE # CLK EPOCH       41  0
                          ORBITAL ELEMENT 1     101  0
                          ORBITAL ELEMENT 2     111  0
                          ORBITAL ELEMENT 3     121  0
                          ORBITAL ELEMENT 4     131  0
                          ORBITAL ELEMENT 5     141  0
                          ORBITAL ELEMENT 6     151  0
                          RADIATION PRESSURE 1  161  0
                          RADIATION PRESSURE 2  171  0
                          RADIATION PRESSURE 3  181  0
                          ALONG TRACK           191  0
                                                  0  0
                                                  0  0
                                                  0  0
                                                  0  0
                                                  0  0
                          
     PREVAL=  0.59179632565998E+00 -0.20732027318210E+01  0.63722845106000E+04
              0.11710230000000E-04 -0.42037335000000E-08  0.00000000000000E+00
              0.22123445948068E+01 -0.13976909467684E+05  0.22548101149911E+05
              0.36932210527633E+04 -0.11970220164939E+01 -0.13320686827172E+01
              0.33985770848327E+01  0.10000000000000E+01  0.00000000000000E+00
              0.00000000000000E+00 -0.24301947287728E+05 -0.36369416390653E+04
             -0.10053296474502E+05  0.15331794338002E+01 -0.16140243063355E+01
             -0.31724316986411E+01  0.10000000000000E+01  0.00000000000000E+00
              0.00000000000000E+00  0.26708660387432E+04 -0.21097415555649E+05
              0.16134956701078E+05  0.23822396282475E+01 -0.16491869581020E+01
             -0.25422889115928E+01  0.10000000000000E+01  0.00000000000000E+00
              0.00000000000000E+00 -0.25674949434566E+05  0.41531392134337E+04
              0.56507320373044E+04 -0.10484303578776E+01 -0.15873965256668E+01
             -0.33654654019434E+01  0.10000000000000E+01  0.00000000000000E+00
              0.00000000000000E+00 -0.81237872687489E+04 -0.98838109221874E+04
              0.23389414394361E+05  0.20904296667312E+01 -0.31751918542911E+01
             -0.66573089221972E+00  0.10000000000000E+01  0.00000000000000E+00
              0.00000000000000E+00 -0.14938585132190E+05  0.10564066754801E+05
              0.19579413854459E+05 -0.31835280614272E+01 -0.82201988393225E+00
             -0.19824156922850E+01  0.10000000000000E+01  0.00000000000000E+00
              0.00000000000000E+00 -0.15948840452290E+05  0.93986557781736E+04
              0.19029837926710E+05  0.52050149665399E+00 -0.32470509987392E+01
              0.20508523425603E+01  0.10000000000000E+01  0.00000000000000E+00
              0.00000000000000E+00

 AVCLK: no valid data for RCLOCK at epoch  50
 AVCLK: no valid data for RCLOCK at epoch  65
 MODEL: warning: receiver clock correction at epoch  202 from PRN03 is enormous: 1.2030E+02 seconds!
 MODEL: warning: receiver clock correction at epoch  202 from PRN03 is enormous: 1.2030E+02 seconds!
 PRN  Ngood
 03   109
 06    89
 08    33
 09   137
 11   113
 12    61
 13   165

7.4  Running CFMRG 

The purpose of CFMRG is to create an M-file to control the combination of C-files and selection of adjustable parameters to be input to the estimation module SOLVE.  SOLVE rewrites the M-file, adding adjustments to the parameters; this updated M-file is then read by CVIEW to calculate predicted postfit residuals.  A sample input batch file follows: 

BATCH
cato                4 letter site code
love                4 letter site code
moja                4 letter site code
pver                4 letter site code
safe                4 letter site code
wsfd                4 letter site code
yknf                4 letter site code
 
  3  6  8  9 11 12 13     Total PRN Numbers 
ccatod.278          C-file
cloved.278          C-file
cmojad.278          C-file
cpverd.278          C-file
csafed.278          C-file
cwsfdd.278          C-file
cyknfd.278          C-file
END
EEEEEEE
mventa.278          M-file
Y                   coordinate partials?
Y                   atmospheric partials? This should be hard wired
  4  4  4  4  4  4  4     Number zenith delay parameters 
Y                   orbital partials?

The structure of the batch file is rather archaic, with many entries present for historical rather than logical reasons.  The first line of the input file specifies batch mode for CFMRG; interactive mode is no longer supported.  This is followed by a site of the 4-letter site codes for the run, a blank line, and a list of the satellites appearing on the C-file.  Next is a list of the C-files to be included, terminated by 'END'.  The next line, a string of 'E's, one for each station, specifies that explicit, rather than implicit biases are to be used.  Next is the M-file name, which must match the name given in the SOLVE batch file.  The 'Y' ('yes') for coordinate partials may be changed to 'N' if sites coordinates are not to be included in the SOLVE parameter menu (for 'ORBIT' mode in SOLVE)).   The 'Y' for atmospheric partials should not be changed.  The number of zenith-delay parameters to be used may be changed, but currently must be the same for all sites.  Finally, the 'Y' for orbit partials may be changed to 'N' if no orbital parameters are to be adjusted and you do not wish to have them appear in the SOLVE menu.  

7.5 Running SOLVE

The principal inputs to SOLVE are the C-files and an M-file.  The phase data, the O-C's, and the partial derivatives are read from the C-files; the parameter menu and pointers are read from the M-file.  The adjusted values are output to the M-file in order to compute the post-fit residuals in SINCLN, DBLCLN, or CVIEW, and adjusted station, orbital, and (optionally) clock parameters are written to new L-, G-, and I-files, respectively, for use in subsequent processing.

SOLVE was originally designed to be interactive in order to facilitate manual intervention in resolving phase ambiguities.  With the increasing size of GPS networks, interactive use is less tractable, and this feature is no longer supported.  With SOLVE version 9.33 we have radically changed the input batch file to replace commands designed originally for interactive operation with commands more easily understood and edited by the user.  The batch file generated by FIXDRV for the 'full' (not 'quick') solution for the sample network discussed in Chapter 5 is shown below with comment lines added to document additional controls.

=============================================================
*   << key-word-controlled batch file format >>             *
* symbol ":" must exist in command lines as separator       *
* any non-blank character at first column means comment line 
* empty after ":" means comment line too                    *
=============================================================
*
-------------- Part 1 -- Files and Global Controls
 operation mode:    batch
 Q-file name:       qventa.278      
 H-file mode:       0
 datum code:        0
 M-file name:       mventa.278      
 quick solution choice:    full 
 biases:                   explicit
 phase difference options: double difference
 combination mode:         LC_HELP
    bias search approach:  decision function
    search path:           narrow lane
    search criteria:       0.15    0.15 1000.00   10.00
 start and end epochs:      1  225  1
 set cutoff_elevation:
    cutoff:  all_sites 15.0
 error model:
    stn_error: all_sites uniform  10.0
    sat_error: all_sats  0.0
*
-------------- Part 2 -- Parameters
 set parameters:
    estimate:   all_sites all_parameters
    fix:        all_sites clock
#   fix:        all_sites zenith
    fix:        all_sites grad
    estimate:   all_sats all_parameters
    fix:        all_sats clock radiation
    fix:        global all_parameters

 exit set:
*

-------------- Part 3 -- A priori Constraints
 set apriori constraints:
    tight_apr_coord:  cato 100.000 100.000 100.000
    tight_apr_coord:  love 100.000 100.000 100.000
    tight_apr_coord:  moja 100.000 100.000 100.000
    tight_apr_coord:  pver   0.010   0.010   0.010
    tight_apr_coord:  safe 100.000 100.000 100.000
    tight_apr_coord:  wsfd   0.010   0.010   0.010
    tight_apr_coord:  yknf   0.010   0.010   0.010
    loose_apr_coord:  all_ 100. 100. 100.
    zenith delays: all_sites  4 PWL
    tight_apr_zenith:  cato 0.500  0.005  100.0
    loose_apr_zenith:  cato 0.500  0.005  100.0
    tight_apr_zenith:  love 0.500  0.005  100.0
    loose_apr_zenith:  love 0.500  0.005  100.0
    tight_apr_zenith:  moja 0.500  0.020  100.0
    loose_apr_zenith:  moja 0.500  0.020  100.0
    tight_apr_zenith:  pver 0.500  0.020  100.0
    loose_apr_zenith:  pver 0.500  0.020  100.0
    tight_apr_zenith:  safe 0.500  0.020  100.0
    loose_apr_zenith:  safe 0.500  0.020  100.0
    tight_apr_zenith:  wsfd 0.500  0.020  100.0
    loose_apr_zenith:  wsfd 0.500  0.020  100.0
    tight_apr_zenith:  yknf 0.500  0.020  100.0
    loose_apr_zenith:  yknf 0.500  0.020  100.0
    tight_apr_grad:  cato 0.030  0.030
    loose_apr_grad:  cato 0.030  0.030
    tight_apr_grad:  love 0.030  0.030
    loose_apr_grad:  love 0.030  0.030
    tight_apr_grad:  moja 0.030  0.030
    loose_apr_grad:  moja 0.030  0.030
    tight_apr_grad:  pver 0.030  0.030
    loose_apr_grad:  pver 0.030  0.030
    tight_apr_grad:  safe 0.030  0.030
    loose_apr_grad:  safe 0.030  0.030
    tight_apr_grad:  wsfd 0.030  0.030
    loose_apr_grad:  wsfd 0.030  0.030
    tight_apr_grad:  yknf 0.030  0.030
    loose_apr_grad:  yknf 0.030  0.030
    tight_apr_orbit:  PN03 1.0E+04 1.0E+04 1.0E+04 1.0E+04 1.0E+04 1.0E+04 1.E+03 1.E+03 1.E+03
    tight_apr_orbit:  PN06 1.0E+04 1.0E+04 1.0E+04 1.0E+04 1.0E+04 1.0E+04 1.E+03 1.E+03 1.E+03
    tight_apr_orbit:  PN08 1.0E+04 1.0E+04 1.0E+04 1.0E+04 1.0E+04 1.0E+04 1.E+03 1.E+03 1.E+03
    tight_apr_orbit:  PN09 1.0E+04 1.0E+04 1.0E+04 1.0E+04 1.0E+04 1.0E+04 1.E+03 1.E+03 1.E+03
    tight_apr_orbit:  PN11 1.0E+04 1.0E+04 1.0E+04 1.0E+04 1.0E+04 1.0E+04 1.E+03 1.E+03 1.E+03
    tight_apr_orbit:  PN12 1.0E+04 1.0E+04 1.0E+04 1.0E+04 1.0E+04 1.0E+04 1.E+03 1.E+03 1.E+03
    tight_apr_orbit:  PN13 1.0E+04 1.0E+04 1.0E+04 1.0E+04 1.0E+04 1.0E+04 1.E+03 1.E+03 1.E+03
    loose_apr_orbit:  all_ 10. 10. 10. 10. 10. 10. 1000. 1000. 1000.
 exit set:
*
---------------Part 4 -- Session Options
 set session_1 options:
    include:       all_sites all_sats
    atmosphere constraint:     N
    ionosphere constraint:     0.0  1.0
    wide lane ambiguity criteria:   0.15  0.15  1000.0 10.00
 exit set:
*
-------------- Part 5 -- Solution Options
 set tight_free solution option:
    print out solution:    q-file ofile
    print out solution:    q-file ofile
    update file option:    m-file l-file g-file
    input_m file name:     mventa.278      
    output_m file name:    mventa.278      
    input_l file name:     lvent7.278      
    output_l file name:    lventa.278      
 set tight_fix solution option:
    print out solution:    q-file ofile
    update file option:    m-file l-file g-file
    input_m file name:     mventa.278      
    output_m file name:    mventa.278      
    input_l file name:     lvent7.278      
    output_l file name:    lventa.278      
    input_g file name:     gvent7.278      
    output_g file name:    gventa.278      
    g_line:  By FIXDRV         qventa.278      rwk       12/22/1993  17:07:50               
 set loose_free solution option:
    update file option: 
 exit set:
 set loose_fix solution option:
    print out solution: 
 exit set:

With the new batch file, almost all of the SOLVE options and constraints can be changed simply by editing the command lines.  In Part 1, for example, you can rerun SOLVE with a different observable or ambiguity-resolution options, for example by changing  combination mode, bias search approach,and search criteria  The combination mode keywords are the same as in the sestbl. for Choice of observable as explained in Section 5.2.  The only ambiguity resolution schemes that have been exercised with recent data are the range-priority algorithm selected by Combination mode = LC_RANGE and tuning of the deviation and sigma of the search criteria, as discussed in Section 5.5.  However, other approaches, including simple rounding and use of an expectation function, are coded and could be invoked by users interested in further research in this area (see Blewitt [1989], Dong and Bock [1989], and SOLVE subroutine bisopt.f) The algorithm and parameters for the widelane resolution are specified in the batch file under Session Options since these depend on instrumentation and ionospheric activity.

Editing the batch file is particular convenient for running quickly different subsets of the data.  To change the span or sampling, edit the start and end epochs line, in which the first value is the start epoch, the second the end epoch, and the third the decimation factor.  To the low-elevation cutoff, edit the numerical value and/or add additional lines:

	cutoff:  all_sites 15.0
	cutoff:  cato 20.0

The error model keywords and values are analogous to those in the sestbl. (Section 5.2), in which you can chose uniform, baseline-length-dependent (baseline), or elevation-angle-dependent (elevation) weights for any or all stations, and/or different weights for individual satellites.  For example,
	
	error model:
    		stn_error: all_sites uniform  10.0
		stn_error: cato elevation 4.3 7.0
    		sat_error: all_sats  0.0
		sat_error: PN09  20.

To fix a parameter, add its name to the list in Part 2; i.e., 

    fix:        all_sites clock  cato long

to fix the longitude of site 'CATO' (Castro Peak).  In Part 3 are given the a priori constraints for sites, orbital parameters, and zenith-delays for both the tight  (user-specified, in sestbl.) and loose (default, for GLOBK) solutions.  The units for all of these inputs are meters for position and meters/second for velocity.  Note that for zenith delays, it is best to use the same constraints for the loose solution as for the tight, since GLOBK does not estimate these parameters.  

To unweight stations or satellites in the solution, use the exclude command in Part 4;  e.g.,  

    exclude:       cato pver pn03 

Part 5 specifies mainly the output files for the run.  You can change the names of any of these if you want, e.g., to make multiple runs with the same data. 

When SOLVE runs it writes output both to standard output (screen or the .log file) and to the Q-file.  The screen output is almost the same as the Q-file but includes also a record of every 50 epochs as the program is running plus and indication of when additional (implicit) bias parameters are inserted as the data are read and the normal equations formed.  An explanation of the Q-file is given in Chapter 5.

7.6  Running AUTCLN

AUTCLN operates on one or more C-files to flag and/or patch cycle slips and unweight questionable data, using all combinations of the available phase and pseudorange data.  The program is executed using a single runstring:
 
   autcln <command file> <out cf series> [....list of cfiles...] OR
                                        [dfile name] <in cf series>
 
where <command file> is an optional command file (commands are given in the ctogobs.hlp file).   If no command file is given (default file generation) then '' should be used as a place holder in the runstring.  If defaults is given as the command file then the defaults willl be printed.  The program will not act on the rest of the runstring.

  <out cf series> is a single characater to denote the new cfile series to be written out.  If no character given (i.e., ' ' used) then no updated cfiles will be written.  Special characters that can be used are:

          .   -- Overwrite the input C-files
          +   -- Increment the C-file series letter, converting numeric series values to a.

    [....list of cfiles...] is the list of cfiles to be cleaned
or
    [dfile name] is the name of a D-file with the list of C- (or X-) files 

    <<in cf series> when the dfile form is used this optional argument can be used to change the input cfile series from that in the D-file.

A sample AUTCLN command file is given in Chapter 6 and copied below.  

AUTCLN Command File
  remove_bias_cond 10.0 3.0 1800.0
  allow_one_bg yes
  use_gamit_elev yes 
  use_cview_edit yes
  remove_first_bia yes 
  dd_return_size 100 25 5 10.
* Site dependent ion parameters
  ion_jump  fair  120  6 2 5
  ion_jump  kour  120  6 2 5
  ion_jump  yell  120  6 2 5
  ion_jump  darw  120  6 2 5
  ion_jump  mcmu  120  6 2 5
  ion_jump  trom  120  6 2 5

A non-blank character in the first column denotes a comment.  All commands are case insensitive.  A complete list, copied nearly verbatum from the on-line help file (kf/help/autcln.hlp) is given below:

end	Last command issued.  An end-of-file (EOF) will have the same effect.
 
rng_jump_tol  [n-allan sd] [min jump (msec)]
Used only for clock statistics, this command specifies the size of a discontinuity in the range O-C that will be considered a clock jump.  The first value [n-allan sd] is the multiplier of the clock stability given by the Allan standard deviation and the second value (min jump (usec)) is the minimum, in microseconds, that will be considered a jump in microseconds; .i.e., both  numbers must be exceeded for a clock jump to be flagged.  The default values are 100.0 and 0.95.
clk_reset_tol [jump difference (msec)]
Tolerance for jump to be taken as a millisecond reset in the clock (msec).  A typical value is 10 msec, but it may need to be increased if apriori clock polynomial (from FIXDRV) does not match the data well (for example due to bad apriori station coordinates or satellite orbits).  The default is set to 100 msec to account for low quality crystal clocks in many receivers.
rng_resid_tol [n-sigma] [min error (m)]
Tolerance for bad range residuals.  The first is multiplier on the sigma of the range data and second is the minimum value in meters.  Range residuals are computed after satellite and station clocks are estimated.  They are equivalent to doubly differenced range residuals.  They are affected by poor station coordinates and satellite orbits.
ion_jump_tol [Reciever code/ALL] [max gap (sec)] [Multiplier] [Min dIon (cyc)]
Lets user set the tolerances for detection cycles slips in the ionospheric delay (LG).  The maximum jump allowed is set by mininum of the [Max dIon] and the maximum of the [multiplier] by the last change in the ion delay and the [Min dIon (cyc)].  That is tolerance will fall somewhere bewteen Min dIon and Max dIon with the intermediate values set by the Multiplier by the change in the previous two data points.  The test will be done for all data points separated by [max gap] or less and all contiguous data.  The default values are 240.  4.  0.8  5.0.  In polar and equatorial regions, max gap should shortened and the Multiplier and Min dIon increased. For polar and equatorial regions, a Multiplier of 6 and Min dIon of 2 cyc will normally stop excessive flagging of data.
rng_noise [Receiver code/ALL] [noise (mm)]
Lets user specify the apriori values for the standard deviation of the range measurements by site (initial values only).  They will be updated during the AUTCLN  run and the updated values reported in the clock and range statistics in the output and summary file.

max_rclk_iterations [max iterations]
Maximum number of range clock iterations.  The solution for the estimate of the satellite and station clocks is iterated to determine the statistics of the range noise and clock Allan standard deviations.  The iteration stops either at [max iterations] or until the convergence criteria are  met.
rel_clk_weight [weight]
Weight to be given to the clock noise model based on previous iteration's estimate of the Allan standard deviations of the clocks relative to data noise while estimating the clocks.  Typical value is to down weight the clock statistics by a factor of 10 relative to the data.
rng_clk_root [range clock root of file names]
Lead part of the name to be given to the range clock solution output.  If no root is given then the range clock solution will not be output.  For example crng will produce output files named crng.PIN1 and crng.PRN_21.  A cplot command file will also be generated called <root>.plt
phs_clk_root [phase clock root of file names]
Lead part of the name to be given to the phase clock solution output.  If no root is given then the phase clock solution will not be output.  See rng_clk_root.
phs_res_root [phase residual root of file names]
Lead part of the name to be given to the one-way phase residual (to the prefit model) output.  If no root is given then the phase will not be output.  See rng_clk_root and residual_site.
sng_diff_root [single difference file root]
Lead part of the name for single difference between stationsfiles  (These may be used with the program mon_data to processing single difference kinematic data).  The single differences are between  first site and subsequent sites.  The residual_site list is used select which sites to write to single difference files, which are only generated if C-files are written out.
residual_site [List of four character codes/ALL/NONE]
Lets the user specify which sites should be output to the phase residual or single difference files
summary_file [Name of summary file/6]
Name of a summary file.  If the command is not given, the summary is written to a file named autcln.sum.  If 6 is given as the file name then the summary is written to standard out.
 rcv_allan_sd [site code/ALL] [Allan standard deviation (ppb@100sec)]
Allows the user to specify the Allan standard deviations of the clocks at each site. These are updated during AUTCLN run. 

remove_bias_cond [Chi**2 Ratio] [min chi**2] [max gap]  <large gap scale>
Sets the constrasts for removing biases.  A bias flag is removed if 
		 X = C2/(C1+min*exp(-C1/min)) > ratio
where C1 is the smallest chi**2 obtained during trial fixes to integer values; C2 is the next smallest; min is min chi**2 in the command; and ratio is Chi**2 Ratio  in the command.  In addition, the gap must be smaller than max gap.  The default values of Chi**2 Ratio, min chi**2, and max gap are 12.,  3., and 3600. (sec), respectively.  The final argument  large gap scale is optional; if it is specified, then the value of X computed from the data is reduced by 1 + large gap scale*atan(gap/min data)) where gap is the gap in the data and min data is the smaller of the number of data in the left and right segments about the gap.  The default value of  large gap scale  is 2.0 
allow_one_bg [yes/no]
Deals with the case where all channels of a receiver slip at nearly the same time.  By specifiying yes you allow AUTCLN to select one channel as a base, patch it roughly in one-ways, and the patch all other channels with respect to it.
use_gamit_elev [yes/no] 
If yes is specified (default), then the cutoff angle specified in the C-file will be used in editing and outputting data, the safest approach for rerunning old data (cutoff passed from the C-file to the X-file via CTOX).  With new data a better approach is to use the min_elev command of AUTCLN and to control use of data by SOLVE with the GAMIT sestbl. input. 
use_cview_edit [yes/no]
Allows user to specify if the CVIEW unweight flag (-1) should be used or not. If yes is specified then the CVIEW unweight flag will not be overridden by AUTCLN.  The default is no.
use_mm_range [yes/no]
Allows user to specify if MiniMac range measurements should be used.  The default is not to use them (no).  (If ranges are not used then MiniMac should be connected to a very good clock.)
ignore_gaps [yes/no] 
Lets user specify that gaps should be ignored when forming acceptable double differences during cleaning.  The default is no; this option should only be used for cleaned data when the  GAMIT elevation cutoff and CVIEW edits are used.
flag_gaps [yes/no] 
Lets user specify if gaps in the one-way data should be flagged with a bias flag.  The default is no, but is automatically set to yes when the allow_one_bg yes is given
gap_size [cf_code/ALL] [number of epochs]
Lets user specify the number of epochs allowed in a gap so that it will not be flagged.  At setting of 1 (default) will cause all gaps to be flagged.  Specifying gap_size automatically turns on  the flag_gaps option.

remove_ms_jump [yes/no]
Lets user decide if millisecond jumps are in the clock are removed when C-files are written.  The default is to remove the jumps (yes).
remove_first_bia [yes/no] 
By default AUTCLN puts a bias flag at the beginning of each one-way sequence as part of its internal bookkeeping.  This has no influence on the SOLVE solution, but the extranesous flags will be removed before C-files are written if yes is specified for this command.  The writing of single-difference files requires the initial bias, so yes should not be specified when single difference files are to be written.
edit_site_sv [Site Code] [PRN] [Start Epoch] [Stop Epoch]
Allows user to specify site/satellite combinations over specific epoch ranges to be edited and not used in determining clock behavior and double difference editing.  Useful for treating bad satellite range data.  ALL may be used delete all sites for a specified specified satellite;  0 may be used for the PRN number to delete all satellites  over the specified epoch range.
phs_fit_tol  [4 values all in cycles]
Tolerances in deciding if a cycle slip has occurred in the pre-fit clock fit to the one-way phase data.  The values and their defaults are as follows:
	(1) deviation of mean phase residual from range solution in pass 1 (1000.);
	(2) deviation of worst phase residual from range solution in pass 1 (500.);
	(3) deviation of pass 2 mean phase from pass 1 phase solution (200.);
	(4) deviation of pass 2 worst phase residual from pass 1 phase solution (100.).  
Values 3 and 4 are normally much less than values 1 and 2.  The actual deviations being flagged can be viewed by setting status_report Pass1_slips Pass2_slips.
status_report [List of options]
Allows user to tailor the output of the program by selecting which quanities will be output.  The options come from the following list:
          CLK_JMP_PROC - possible clock jump detection
          CLK_JMP_VAL  - value of clock jump when one is found
          BIAS_ADDED   - BIAS flag added during one-way phase processing
          PASS1_SLIPS  - Number of cycles added in Pass 1 one-way clean
          PASS2_SLIPS  - Number of cycles added in Pass 2 one-way clean
          DD_TRIALS    - List each double difference combination tried
          DD_ESTIMATES - Estimates of cylcle slip during the DD fix.
          DD_SCAN      - Details of scan flag showing sites and svs used.
          ELEV_DIST    - Distribution of final (weighted) data by elev
          RUN_PARAMS   - Dump of parameters used in run.
ALL may also be used, and then -option to turn off particular output; e.g., status_report all -clk_jmp_proc.  The status reports are sent to standard out.

dd_report  [DD Report file name] [option]
Allows user to specify a file of the format readable by CVIEW and to specify which types of double differences should by output to this file (i.e., ALL, FIXED, NOT_FIXED).  If the file name dd.srt is used then the file can be directly read into CVIEW to allow checking of the cleaning results.
min_elevation [Min clean elevation (deg)] <Min output elev (deg)>
Minimum elevation to which data will be cleaned. Once this value has been set in AUTCLN, the data below this elevation will not be useable later without further cleaning.  The minimum output elevation is optional and is the elevation cutoff to be applied when the C-files are written.  This command is ignored if use_gamit_elev = yes.
trim_oneway_tol [min_dtl_bias] [min_good_bias] [min_dtr_end] [min_good_end]
Set the tolerances used in triming the one-way data to remove small segments of data (defaults in parentheses):
	min_dtl_bias  - mininum time in seconds between bias flags (120 s)
	min_good_bias - mininum epochs between bias flags and maximum 			      epochs over which a bias flag will be removed in one-way data (8)
min_dtr_end   - Fraction of total duration of data allowed for a bias flag at the end 			   of the one-way sequence (0.1) 
min_good_end  - Number of epochs of data allowed after last bias flag (24)

dd_return_size [Max WL] [Max LC] [Max LG] <One way fix tol>
Set the number of data to be used for cycle skip repair (defaults in parentheses):
Max WL - widelane estimates (100), applies to one-ways
Max LC - LC (50), applies to double differences
	Max LG - LG (10), applies to one-ways or double differences
These values should be decreased if there is significant curvature in the data, which might apply particularly to LG with a high ionosphere.  They cannot be set less than 5.  One way fix tol is an optional argument that sets the maximum duration over which one-way L1/L2 range data will be be patched using the widelane and LG.
dd_fit_tol  [WL Ratio] [WL Min] [WL Max] [LC Ratio] [LC Min] [LC Max]
Set the tolerances for flagging cycle slips in wide-lane [WL] and LC double differences [LC] (defaults in parentheses):	
	Ratio - Ratio allowed for jump compared to local rms or last  change (4.0)
	Min   - Minimum value for a jump that will be flagged (cyc) (WL  0.8,  LC  0.5)
	Max   - Maximum value above which all jumps will be flagged (cyc) (WL  4.0,  LC  1.0)
(The tolerance on the maximum jump allowed will fall between Min and Max with the intermediate values set by [local rms] x [ratio])

scan_site [All/None/list of site names]
Lets user specify which sites should be scanned before double difference cleaning.  If unflagged slips are found during double difference cleaning this command should be used. All will  set all sites to be scanned; clear will set no sites to be scanned.  A minus sign before a site name will remove this site from list (e.g., -PIN1 will remove PIN1 from the scan list.)
max_scan_edit [number]
Lets user set the threshold for the number of double difference bias flags that can be added during scanning before the complete station/satellite set of one-way data is edited. (The default is not to apply this editing condition).  For non-AS data the number can be set small (~10).  For AS data, <50 will excessively delete old Rogue data.  This control is used to automatically delete bad stations and satellites experiencing burns.
np_set [size (epochs)] [Start (epochs)]
 Form normal points with phase and range data using groups of [size (epochs)] points.  For 30 second data, size=15 forms 7.5 minute normal points.  The value must be odd.  [Start (epochs)] sets the starting epoch for forming normal points.  If the value is negative then normal points will not be formed but the editing necessary to form the normal points will be applied to the data. (This feature is useful for testing the effects of the approximations inherent in the normal point formation.)
site_params [site/ALL] [Min Clean El] [Min Out El] [Min L1 SNR] [Min L2 SNR]
Allow site specific parameters to be specified:  
 [Min Clean El] - minimum elevation angle to which data will be cleaned (degs)
[Min Out El] - minimum elevation angle to be used for output of  C-files (deg).			[Min Out El] must be greater than or equal to [Min Clean El]   (By cleaning to 		a lower elevation angle, more data are available for detecting and fixing cycle slips)   
[Min L1 SNR] - minimum SNR value to be used at L1.  Setting this to 0 will allow all 		initially into the solution. (same as Pre 2.13 Versions of AUTCLN).  
 [Min L2 SNR] - minimum SNR value to be used at L2.  
The default values for these parameters is set based on receiver type.  If the min_elevation command is used after the site_params command all stations will be given the cut-off elevation angles specified in the min_elevation command. 

AUTCLN produces two output files, a step-by-step log of the editing process (autcln.out) and summary (autcln.sum). In order to interpret either of these, it is necessary to understand the algorithms used in the editing.  Since the steps are made in sequence with results from previous steps used, errors in one stage of the processing usually cause erors in later stages.  Also errors at one station or on one satellite can effect the results from other stations and satellites.  There are seven major steps in the process:

(1) Clock error estimates for sites and satellites based on range data.  This analysis is iterated until there is convergence between iterations for the estimates of clock statistics.  The maximum number of iterations can be set.  Range data can be edited by the analyst if they is not consistent with data from other sites and satellites.  In the default settings for autcln, bad range data are typically un-deleted in the second iteration if there are lots of bad range measurements.

(2) Clock error estimates for sites and satellites based on phase data.  The clock errors from the range data are used as a priori values for estimates from phase data.  During this analysis, large jumps in the phase data can be detected and the number of cycles of phase needed to make the range and phase consistent are computed.  Changes in the ionospheric delay estimates from phase data are also used to detect jumps in the data.  When jumps are detected, bias flags are added.  Bad range or bad prefit residuals can cause an excessive number of bias flags to be added at this stage.  The adding of bias flags and the number of cycles removed with each bias flag are reported in the output of AUTCLN.  The default ionospheric jump detector parameters are too tight for polar and equatorial regions and can be changed by station in the command file.

(3) The default action next is to add bias flags to all gaps in the data.  This can be changed in the command file, but is not recommended.

(4) The default action next is to scan all contiguous one-way data and to form double differences with triplets of the data to see if there are jumps in the double differences.  When a jump is found, more double differences are formed to assess if the one-way data being analyzed have the jump.  (This is done by switching the satellite and station to see if the jump persists.)  Bad prefit residuals can cause many biases to be added at this stage.  Unmodeled accelerations of the satellites can also cause many bias flags to be added at different stations.

(5) Cleaning of data using as many observables as possible.  This step involves trying to assess the number of cycles of slip at each bias flag in the one-way data and whether the bias flag can be reliably removed.  Small segments of data (i.e., closely spaced bias flags) are removed before any attempt is made to resolve biases.  Three criteria are used to compute the number of cycles: (1) continuity of LC, (2) continuity of LG, and(3) continuity of the widelane.  Different number of data are used in each of these with the widelane typically being the longest and LG the shortest.  The sequence AUTCLN uses is to first try to resolve the integers in one-ways if P-code L1 and L2 range data are available using the widelane and LG continuity.  If this fails then double differences are used and LC continuity is also considered.  The default setting in autcln is to not allow one-way bias flag removal because this became unreliable once AS was turned on.  To patch in double differences, AUTCLN finds another station and satellite combination which does not have a bias flag or gap around the time of the flag which is being evaluted.  Stations and satellites are scanned in sequence until AUTCLN finds a combination that can be used to remove the bias flag or runs out of stations and satellites to try.  The default is to output a line for each combination tried.  The last one output is the one which was used to determine the number of cycles.  A common occurrence is that all satellites at a station have bias flags at or near the same time (due to a power failure for example).  In these cases, there is an optional feature to "allow one bias or gap" (the allow_one_bg command) at this time.  In this case, autcln first determines if bias flags can be removed if it ignores the bias flags on both satellites being used in the double difference.  If the bias flag can removed, then it resolves the cycles slips on the first one-way data sequence to be tested and removes the bias flag.  When later bias flags are encounted at this time for this station, they will be patched relative to the first one-way sequence where the bias flag was removed.  "Force?  T" appears in autcln.out for those bias flags removed this way.  (There is no explicit book keeping to ensure that this happens).  When data are very "broken up" with many bias flags and gaps, AUTCLN can make mistakes in this procedure, so this is normally the most unreliable part of the cleaning process.  Only loss of lock on all satellites at a station is treated in this way.  If all stations lose lock on a satellite at the same time then the bias flags will be not removed unless they can be patched in one-ways.  While data are being used for patching, they are also checked for jumps.  When a jump is found, autcln scans each of the one-way sequences, checking to see if there are cycle slips in them.  Because more data are used than when the jumps were first detected, this test is more sensitive than the orginal scanning and sometimes detects jumps that had not been previously detected.  In many cases, these jumps are noisy data and the added bias flag is later removed (and sometimes added back again later).  Jumps detected this way can be found in the output by grep'ing on LCDD.  If they are large, then AUTCLN has become confused about where a slip is located and this can cause problems.The cleaning loop is iterated four times since data with bias flags resolved late in the cleaning loop may be used to resolve biases on data looked at earlier.  There are some differences between the iterations.  In the first iteration, allow_one_bg is not used.  This is so that as many bias flags as possible are resolved before it is attempted.  On subsequent iterations, allow_one_bg is invoked on increasingly larger gaps in the one-way sequence.  It starts at about 10% on the maximum gap size over which biases will be removed, and increases by about 5% each iteration.  After the first iteration, large gaps in the data are no longer considered (i.e., we will never be able to remove these bias flags).  

(6) Data trimming.  In this step, short sequences of data between bias flags are removed and the length of data after the last bias flag on each each one-way sequence is checked as a percentage of the total number of data on the sequence.  If this percent is too small then the data are removed and the process repeated.  This is done so that SOLVE will have a long sequence of data for resolving biases.  (Double differences are not checked at this point, so it is possible to get bias flags which have only a small number of data available for their determination.)

(7) Normal pointing (optional).  Normal points can be formed at this point.

The tables in the autcln.sum file summarize the results of these steps:

Clock Statistics

 Clock and Range noise statistics at iteration  3
 Site/PRN    Allan SD@100  #     Range rms    #
             sec  (ppb)            (mm)
 BRLD       19.761493   2832          596.9  16210 TRM
 KAIN       19.931665   2879          675.1  15939 TRM
 KIT3         .527232   2879          729.9  16307 TRB
 KUM6       10.105467    719         2061.0   3462 TRM
 KUMB       20.533951   2879          471.6  16378 TRM
 WETT         .010000   2808          240.9  15224 ROG
etc.
 PRN_01       .384611   1188
 PRN_02       .411166   1039
 PRN_05       .422517    984
 PRN_06       .397293    916
 PRN_07       .414031   1237

This table gives estimates of the clock Allan standard deviation (in parts-per-billion) and range noise rms for each receiver.  These clock statistics are based on range data only.  The example shown is typical for non-AS conditions with SA active.  Under AS conditions the range noise for a Rogue SNR-8 increases to 1000-2000 mm, and Trimble SSE and TurboRogue increase to 800-1000 mm.  Values much larger than these usually mean lots of bad range data or bad prefit residuals (station coordinate errors of >10 m).  Very bad range data can be seen with AVCLCK errors in the MODEL output P-file.  Also autcln.out will list bad range measurements (but sometimes here the station or satellite may incorrectly listed especially when there is a lot of bad data).  If there are AVCLCK errors, then the edit_site_sv command can be used to pre-edit these values in AUTCLN.

Scanning Summary

 DDScan bias flags added report for pass  1
 SITE PN01  02  05  06  07  09  14  15  16  17  18  19  20  21  22  23
 BRLD    6   2  10   8  14  18   6   4  10   2   4   2  12   6   6   4
 KAIN    0   0   0   0   0   0   0   0   1   0   0   0   0   0   1   0
 KIT3    0   0   0   0   0   0   0   0   0   0   0   1   0   0   0   0
 KUM6    0   2   0   0   2   4   0   0   0   0   0   0   0   0   0   0
 LHAS    0   0   0   0   0   0   0   0   0   0   0   0   1   0   0   0

This summary lists the number of bias flags added by site and satellite during double difference scanning of the phase data.  Large values here can mean either bad prefit residuals or bad phase data.  The max_scan_edit command can be used to automatically delete all data on a station/satellite combination which has too many bias flags added during double difference scanning.  Many bias flags being added to a satellite at many stations usually represents the effects of an unmodelled acceleration of the satellite.  Rogue SNR-8 often have many bias flags added when AS is on.

Data Editing and Bias Flags Remaining

 DATA AMOUNTS 
(Good: # good data; Gap: # deleted in gaps; BF: # bias flags  < 2*max separation)
 SITE  PRN Good  Gap  BF  PRN Good  Gap  BF  PRN Good  Gap  BF  PRN Good  Gap  BF
 FORT PN01  657    0   0 PN02  699    4   0 PN04  649    0   0 PN05  681    0   0
      PN06  945    0   0 PN07  133    7   0 PN09  648    0   0 PN14  477    0   1
      PN15  444    0   1 PN16 1119    2   2 PN17  813    0   0 PN18  782    0   0
      PN19 1047    0   0 PN20  470    6   2 PN21  962    0   0 PN22 1125    0   0
      PN23  659    0   0 PN24  573    0   1 PN25    0    0   0 PN26 1132    0   0
      PN27 1058    0   1 PN28  640    0   0 PN29 1032    0   0 PN31 1128    0   0

These lists (one per station) show by satellite the number of good data in the one-way sequence, the number of data deleted in gaps between closely spaced bias flags, and the number of remaining bias flags that might be resolved (i.e., number bias flags separated by less than twice the maximum size over which bias flags would be removed).  Large numbers in the gap columns and/or large numbers of remaining bias flags usually mean bad prefit residuals or noisy data.  Usually, the numbers in Gap column increase when AS is on especially for SNR-8 receivers.  More than 3 bias flags remaining usually indicates that the data is noisy and broken up into small pieces.  (Bad data at one site can often lead to additional biases at other sites, so it usually the site with the most bias flags that is causing the problems.)

Elevation-angle Statistics

ELEVATION ANGLE HISTOGRAM
SITE  0- 5  5-10 10-15 15-20 20-25 25-30 30-35 35-40 40-45 . . . 65-70 70-75 75-80 80-85 85-90 Min (dg)
BRLD    0     0     0    93   108   114    77    82    66        47    63    39    20    13  15.66
KAIN    0     0     0    62   116    94    97    91    76        60    50    35    22     8  15.91
KIT3    0     0     0    95   118    94    85    83    84        72    50    37    17    12  15.47

This table shows the number of good data or good normal points in elevation bins. Correctly operating receivers should have about the same number in 15-20  degree bin as in the 20-25.  (The above example is for 24 hours with 15-point normal points).

Bias Flag Report

This report provides an overall summary of the number of bias flags in the clean data and why they were added.

 BIAS FLAG REPORT: Types
 ORG-Original  JMP-Big Jump   ION-Ion Jump   GAP-Data Gap   DDS-DD scan    WLS-Wide Lane  DDC-DD cleaning
SITE       # Flagged        |      # Remaining       |     # Edited           |    # with jump
    ORG JMP ION GAP DDS DDC | ORG JMP ION GAP DDS DDC| ORG JMP ION GAP DDS DDC| ORG JMP ION GAP DDS DDC
BRLD  33   6   0  25 137   0|   0   0   0   0   0   0|  28   2   0  25 136   0|   5   4   0   0   0   0
KAIN  42  11   0 105   7   0|   0   0   0   0   0   0|  34   4   0 100   3   0|   8   7   0   0   0   0
KIT3 111   0   1  11   3   0|   0   0   0   1   0   0| 109   0   0  10   3   0|   2   0   0   0   0   0
KUM6   0   0   0  35  10   0|   0   0   0   0   0   0|   0   0   0  35  10   0|   0   0   0   0   0   0
KUMB  36  14   0  98   1   0|   0   0   0   1   1   0|  30   8   0  93   0   0|   6   6   0   0   0   0
LHAS  54   1   0  34   3   0|   4   0   0   0   0   0|  50   1   0  32   2   0|   0   0   0   0   0   0
OTM5  26   6   0   8   1   0|   0   0   0   0   0   0|  21   5   0   7   1   0|   5   1   0   1   0   0
OTM6  45   7   1   6   4   2|   1   0   0   0   0   0|  42   6   1   6   3   1|   2   1   0   0   0   0
OTMK  38   5   2 115   5   2|   0   0   0   2   0   0|  27   2   2 106   5   2|  11   3   0   2   0   0
POL2 186   0   1  47   4   0|   0   0   0   0   0   0| 183   0   1  46   4   0|   3   0   0   0   0   0
TALG  49   0   0  90   0   0|   0   0   0   3   0   0|  49   0   0  48   0   0|   0   0   0   0   0   0
TOS1  40   5   0  49   6   0|   0   1   0   0   0   0|  36   1   0  48   3   0|   4   3   0   0   0   0
TURG  39  15   0  17   0   0|   0   0   0   1   0   0|  38   6   0  16   0   0|   1   9   0   0   0   0
WETT  52   0   0   5   2   0|   5   0   0   0   0   0|  47   0   0   5   0   0|   0   0   0   0   0   0

The report is in four sections:
# Flagged are the numbers of bias flags added or encountered during cleaning (Entries explained below).
# Remaining are the numbers of bias flags left in the cleaned data.
# Edited are the numbers of bias flags removed by deleting the data affected by the bias flag (as opposed to the bias flag removed by reliably resolving the integer number of cycles at the flag).
# with jump are the numbers of bias flags which were resolved to non-zero integer values.  The difference  #Flagged - (#Remaining+#Edited+#with jump) gives an idea of the number of bias flags added that were not really needed.  (It is not possible to tell how many real jumps were in the edited data). 

When data are normal pointed the number of remaining bias flags will not necessarily be the same as the sum of the values shown in the "Data Editing and Bias Flags Remaining"  report because this latter report is generated before normal points are formed, and some bias flags reported in the #Edited columns are not present if the data are deleted during the normal point formation.

Within each of these categories, the reasons for adding the bias flags are given:
ORG is the number of original bias flags in the data (loss-of-lock indicator set in the rinex file).  There is not much the user can do about these if they are large, other than to conclude that the receiver itself was not very happy.
JMP is the number added due to large jumps between the phase and range estimates of the clocks.  Large values here can indicate very bad prefit data (e.g. when site positions are 100's km in error) but most often indicate bad range data.  Very bad ranges (>300 m) will generate AVCLCK errors in MODEL, and smaller range errors can be detected by the reports of biases added in the one-way phase fitting.  The tolerances for these fits can be increased to stop the bias flags being added, or the intial range data can be deleted.  (These are often low elevation data that will not be used in the final analysis anyway.)
ION is the number of bias flags added in the ionospheric jump detector.  Again the tolerances can be increased so that these jumps are not detected.  This jump detector is independent of both the range and prefit model quality.  For equatorial and polar sites the detector tolerances should be loosened.(e.g.,  ion_jump_tol  yell  30 6.0 2.0 5.0)
GAP is the number added due to gaps in the data.  There is not much that the user can do about these since they result from gaps in the data.  If the SNR is being used to flag data, reducing the SNR limit can make these values smaller.
DDS is the number of bias flags added due to discontinuities in the double difference data.  Large values here indicate poor quality phase data or bad prefit residuals.
WLS is the number of bias flags added due to jumps in the widelane observable.  The widelane jump detector should be loosened for AS data. (In the example used here all these values were zero, so the WLS column has been cut out to reduce the table width.)
DDC is the number of bias flags added during cleaning.  Large values here are very bad because all the jumps in the data should have been detected before cleaning starting.  Grep'ing on LCDD in autcln.out will show the magnitudes of the jumps.  Most often these are just above the tolerances for detection and simply reflect the increased sensitivilty of the detector used during cleaning.  Large jumps usually mean that AUTCLN has become confused as to which one-way a jump occurs on and is trying to patch it in the wrong place.  Often deleting some of the data around these times is sufficient to remove the problem.  Grep'ing on the epoch number (with a space on either side) shows the manipulations of all data at this epoch, including which stations and satellites were used to do the patch.  This can be useful in tracing what happened during the cleaning.

Editing Report 

This report shows the parameters used at each station for the editing.and why data were eliminated from the analysis.

 EDITING REPORT AND SITE PARAMS
 SITE  MnOUT  MnCLN  SNR   LSNR GF03 BEND BCLS NPED GF-1 GF04 DDSC  BDL2 NODD ELCL EDIT MMRG ELEV        Good
   (deg)  (deg)  L1 L2
 BRLD  15.00  10.00  2  2   135    0    0  135 1480    0 1453    0    0    0    0 1478  322    0   51  14595
 KAIN  15.00  10.00  2  2   238    0   20   95 1469    0 1572    0    0    0    0 1590    0    0   23  14355
 KIT3  15.00  10.00  5  4     0    0  137   49  611    0 1588    0    0    0    0 1667    0    0  445  15510
 KUM6  15.00  10.00  2  2    74    0   12   52  458    0  262    0    0   73    0  262    0    0    5   2940
 KUMB  15.00  10.00  2  2    37    0    0   97 1626    0 1335    0    0    0    0 1353    0    0   18  14655
 LHAS  15.00  10.00  5  4    26    0   98   21  856    0 2405    0    0   26    0 2440    0    0 1047  14985
 OTM5  15.00  10.00  2  2    44    0    0   52  246    0  231    0    0    0    0  237    0    0    8   3195

MnOUT is the minimum elevation angle to be used when writing out the C-files.
MnCLN is the minimum elevation angle used during cleaning.  By including lower elevation data for cleaning, there is more chance of finding double differences.  The disadvantage is that low elevation angle data can be of very poor quality for some receivers.  Also we have seen cases where the low elevation angle data appears to be values generated by the model in the receiver and therefore is very smooth but inconsistent with the real data.  This really confuses AUTCLN because the data appear very good and often autcln will remove the real data because they are so much noisier than the "model" data.
SNR L1 and L2 are the signal-to-noise ratio (snr) limits used by station.  There is some inconsistency in the snr limits used by different RINEX translators especially for Rogue SNR-8 data.  The values above (for KIT3 which is a TurboRogue) are for Rogues translated by JPL's SRX program.  (Strictly, 4 means SNR<0 in the SRX converter, but there seem to be lots of good data with snr of 4 so we accept these data.  RGRINEX running on SNR-8 data will have snr values as low as 2 and these are often good data.  An  snr of 1 in the RINEX standard means bad data and hence the limits should never be less than 2.  0 or blank in the RINEX file for SNR will NOT be edited by AUTCLN since by definition these values mean no information is available.

The meaning of each column is the number of points (before normal pointing, but after data for normal pointing has been selected) edited for the given reason.  Data points can have mulitple reasons for being edited.

LSNR -- SNR value at either L1 or L2 below the set limit
GF03 -- GAMIT low amplitude flag (rarely if ever set by the current MAKEX).  
RCLK -- Large difference between autcln's estimates of the station clock and the value actually used in model (not implemented currently and cut from table displayed here to reduce the table width )
GF02 -- GAMIT bad data flag.  Indicates that the receiver is not tracking; usually denoted by an L2 SNR of 2.  This flag may be set by MAKEX but also set by AUTCLN if the L1 and L2 range values are exactly equal.  (All were zero in the table displayed here so they have been cut to reduce the width.) 
BEND -- Bias flags were too close to the end of the data.
BCLS -- Bias flags were too close together.
NPED -- Data could not be used in normal point but was OK otherwise (usually about 10% of the total amount of good data for 15-point normal points).
GF-1 -- GAMIT marginal flag.  Usually zero for raw data but is set when data are cleaned in CVIEW.  Reprocessing of AUTCLN output C-files with edit_site_sv used in the command file will set this flag.
GF04 -- GAMIT elevation cutoff flag (set in MODEL).
DDSC -- Too many bias flags were added during double difference scanning so the whole one-way sequence was deleted.
INTR -- Interactive edits (not implemented and not shown in the displayed table).
GFUN -- GAMIT flag of unknown type (should be zero; not shown in the displayed table).
BDL2 -- SNR edits for L2 only (i.e., L1 SNR was good).
NODD -- Data for which no double differences could be formed (not implemented, but should be flagged if separate AUTCLN runs are to be combined).
ELCL -- Data edited below cleaning elevation angle.
EDIT -- Data edited by edit_site_sv command
MMRB -- Data flaged with the use MiniMac range = no command.
ELEV -- Data flagged below the output elevation angle.
Good -- Number of good data remaining that will be used in the SOLVE analysis.

At the end of the autcln.sum file is a list of the parameter values used in the run.

The information written in autcln.out can sometimes be helpful in determining how AUTCLN handled data at a particular epoch.   Given below is an explanation of the lines appearing in the file:

DD_Trials line
..............
Ep 114   S1/C1 2 13   S2/C2 1 2   dL1/2 slip 0.0  0.0 cycles   NumLR 23 18  
EpLR 111 114   dchi, Chiqual 1.7 102.9  30.3

	Ep is the epoch number
	S1/C1 is site number and channel for one way
	S2/C2 is site number and channel for double difference.  If these values are zero then there was no double difference formed.
	dL1/2 slip is the change in number of cycles at L1 and L2
	NumLR is the number of data in left and right segments (May actually be less than this if unflagged bias found.
	EpLR  is the epoch numbers across the gap or bias flag being patched
	dchi, Chiqual are the lowest two chi**2 increments when integer cycles are tried, and  the ratio used to see if bias flag can be used.

Bias Flag line  (always printed)
 
Epoch 114   Site MOJ1 PRN 20   L1  from   0.0 to  0.0  L2 from  0.0 to  0.0
Reliable?  T   30.44   BFLG   OneBG F   Force F
where the first line designates the epoch, site, satellite and cycles added in L1 and L2
Reliable? T  indictates that the bias flag was removed, and the value following is  Chiqual
BFLG or GAP says whether a bias flag or gap is being patched
OneBG T or F gives the value of the OneBG flag (see commands)
Force indicates whether (T) or not (F) the one-ways were forced to have the bias flag removed so that  other combinations could have one bias or gap.