TRACK: GPS differential phase kinematic positioning program For further documentation, see http://geoweb.mit.edu/~tah/track_example TRACK Version 1.27 GPS Kinematic positioning program ------------------ --------------------------------- Usage: % track -f <command file> -a <ambiguity file> -d <day> -w <week> -s <S01> <S02> .. <S10> where <command file> is a required file containing a list of commands to control the program (see below) <ambiguity file> is an optional file containing a modified set of integer bias parameters and settings (see full description below). <day> the string in this argument replaces <day> in the command file lines (e.g., bas1<day>0.03o will become bas12220.03o if the -d 222 option is given. <week> the string here will replace any <week> strings in the command file (useful for the nav_file name which could be a week of concatinated sp3 files. <S01>, <S02> .. <S10> are upto 10 strings that can be replaced in the command file i.e. the string <S01> in the command file will be replaced by the first string, <S02> by the second and so on. If one the strings is called space (all lower case), the corresponding <SXX> entry will be replaced by a blank character (This provides a means to un-comment lines) Version 1.27 2011/12/27 ----------------------- Added Relative humidity argument to USE_GPTGMF command for compatability with GAMIT use of GPT. Default left at 0.00 (used 0.50 for GAMIT compatability). Version 1.26 2011/11/23 ----------------------- Added reading of ionex files (IGS format) which are interpolated to yeild ionospheric delay estimates, added new LOS ion file that can directly read fixed a bug in EXWL chi-squared contribution in ambiguity fixing (should improve long-baseline ambiguity resolution, improved bias fixing iterations, Added atm_scale option for kinematic site atmospheric delay estimation (Scale factor for atm-delay/height difference partial). New MIN_TOLS command which sets minimum values (had been hard wired in prior versions) New commands IONEX_file for IGS ion files and IONLOS_file for line-of-sight ionospheric delay estimates (generated by smooth L1-L2 phase differences). Version 1.25 2010/11/13 ----------------------- Introduced a dump file as an output option and fixed bugs with multistation residual rms calculations. Added differerntial code bias (DCB) calculations to account for biases in C1 versus P1 pseudoranges. New commands DCB_FILE and RCV_TYPE. Also added receiver type to ANTE_OFF command for convenience. Version 1.24 2010/06/01 ----------------------- Added features from trackRT. Rinex files simply concatenated, velocities in site_pos command and new commnd TIMEDEP_PROCNS Version 1.23 2010/02/15 ----------------------- Fixed problems with ambiguities being found to be not-dependent (increased search depth). There still seems to be problems with short-files in multibaseline processing. These sites should be put imediately after fixed site (seems to solve problem). Resorted ambiguities when O (other) status during fixing stopped the ambiguity being resolved. Fine tuned the post-fit editing so that large RMS values would be edited. Changed some formats and added site names in addition to site numbers. Removed SEARCH option completely. Version 1.22 2009/10/17 ----------------------- Added feature not to set bias flag at jumps in the MW-widelane due to millisecond jumps in pseudoranges (these jumps should not be present). The set_msec_bf command can be used to force a bias flag to be added at these jumps. Version 1.21 2009/01/11 ----------------------- Fixed problems with discontinuities in back solutions. Added correlation between height and atmospheric delay estimates to NEU output. Fixed some issued with ambiguity assignment. Introduced two new commands: USE_GPTGMF to set atmospheric model to use (MTT is the default) and REF_NEU which sets XYZ coordinates of the reference point forcomputing NEU positions relative to. (First site in obs_file list is the default). Add command TIME_UNIT for time unit on process noise Version 1.20 2007/10/29 ----------------------- Significant updates to the float ambiguity resolution code and default tolerances have been changed. Added commands usr_addbf and usr_delbf to allow users to add and remove bias flags. Atmospheric delay estimation changed with introduction of height rate term (See model description ATM_STAT) Relatve rank limit input added to float_type command (can also be changed with amb_cycle command). Data noise model changed to add elevaiton angle dependent weight factor (See DATA_NOISE). Default data noise reduced to make more consistent with phase RMS scatter. New default is 0.003 0.003 1 1 0.5 where 0.5 is elevation angle weight term. Added upto 10 replacement strings that can be used in command files. Provides a means of dynamically changing command files through the runstring. Clock error test is sensitive to aproiri sigma on site positions ('Bad Clock estimate' error message). Using site_stat to increase apriori sigma to larger values (eg., 1000 m) can solve this problem. Version 1.14 2006/12/28 ----------------------- Added phase center models for both stations and satellites. New commnd ANTMOD_FILE specifies ANTEX format file to be used, ANTE_OFF command modified to allow antenna specification. Antmod_file command may be specified multiple times but MUST follow the obs_file and ante_off commands. Version 1.13 2006/03/02 ----------------------- Added reading SP3c orbit file format and included support for Block IIRM satellites (PRN17 being the first). Small changes in est_pos to better handle bad pseudorange data. Version 1.12 2004/12/26 ----------------------- Added MWWL_JUMP comamnd to control size of MW-widelane jump that will flagged as a cycle slip. (Default 5 cycles) Version 1.11 2004/11/23 ----------------------- Some small bug fixed and added output of atmospheric delays at fixed sites Version 1.10 2004/04/28 ----------------------- Introduced STOPGO_MODE for rinex files that have the correct stopgo records in them. In this mode, when a stop (receiver static) line is found, the process noise on the site is reduced to a small value (10^6 times smaller than the kinematic process noise). When the GO rinex record in found, the process noise in increased again (see STOPGO_MODE command under commands). Version 1.09 2003/07/28 ----------------------- Improved the cycle slip detection using the MW widelane Added new command EXCLUDE_SVS to allow whole satellites to be deleted (feature needed when a satellite is not in sp3 file or only partially in sp3 file) Added new commands RWL_root which will output the raw wideline information used by tracked to detect cycle slips. SUM_FILE is a summary file containing the INITIAL and FINAL ambiquitity parameters and the statistics of the data residuals. Added res_root (root for postfit residual files) to the help file Added statistics of data residuals as a function of PRN and elevation angle. Added solid-earth tide corrections and GPS satellite phase center offsets. Version 1.08 2002/06/20 ----------------------- Added phase data editing if the epoch RMS exceeds a set tolerance Aadded automatic correction of mill-second time jumps in phase in Ashtech uZ receivers Version 1.07 2002/03/22 ----------------------- Bug fixes and work-arounds to get track to run with HPUX11 and f90 Version 1.06 2002/02/05 ----------------------- Changed the cycle slip detector from a combination of one way and double difference to a station-station single difference detector. The resultant algorithm is more robust and deletes less data. Introduce a new diagnostic to allow easy assessment of why biases are not fixed in particular iteration. A 5-character string Fcode was added after the Fix status in the floating point bias fixing report that reports which fixing criteria were not statisified. For float_type LC the Fcode is S -- Floating point estimate sigma too large (Sig Limit) W -- MW WL sigma too large R -- Relative rank not large enough C -- Chi**2 increment too large for the best choice of ambiquities O -- One other bias in the double differences not fixed yet. For float_type L1+L2 the Fcode is S -- Sigma too large at L1 S -- Sigma too large at L2 R -- Rel rank not large enough at L1 R -- Rel rank not large enough at L2 O -- One other bias in the double differences not fixed yet. Example below show cases not fixed due to (1) relative rank, (2) Floating point sigma too large and one other bias not fixed (3) None of the criteria are satisfied (when the floating point sigma is too none of the other criteria are actually checked). * BF S PRN Epoch Range F Estimate dLC Sig Limit Relative Rank Fix Fcode Change L1 L2 Residual L1 L2 Fits Best LC WL LG 175 5 PRN 15 1 43 1 1.86 +- 0.24 SL 0.25 RR 2.36 F F --R-- dL1,2 3 3 dL12 0.31 -0.08 Fits 11.7 0.8 0.3 105.7 48 2 PRN 07 1 429 1 -0.16 +- 0.74 SL 0.25 RR 9660.51 F F S---O dL1,2 0 0 dL12 -0.28 -0.02 Fits 0.4 0.1 0.1 2.1 50 2 PRN 15 1 52 1 -0.18 +- 2.11 SL 0.25 RR 0.00 F F SWRCO dL1,2 0 0 dL12 0.00 0.00 Fits 0.2 0.0 0.0 1.5 An error in the bias fixing when one of the other biases is not already fixed fixed was corrected. Reduced the output associated with missing clock values in SP3 files. Now only the number is reported rather then the specific values missing. Version 1.05 2001/06/16 ----------------------- Added an ionospheric constraint to the floating point resolution of ambiquities. This make the bias fixing much more reliable on shorter baselines and when the range data is noisy or systematic. Modified some of the handling of Wide-lane calculations to make them more robust and added some additional status information during float ambiquuity resolution. Increased the documentation on the FLOAT_TYPE command and the discussion of the floating point ambiquity resolution with emphasis on which parameters to change to help resolve ambiquities. Fixed a small problem with the first epoch output for kinematic sites. Modified some defaults to give better performance in default mode. Version 1.04 2000/08/23 ----------------------- No new features, made code more robust to file formats. Two main changes: (a) changed the reading of NAV files to allow for extra values in the teqc generated nav files. (b) Modified the epoch calculation from the rinex files to allow for for large differences from the nominal time tags when long rinex files are generated (> 1-2 days). Version 1.03 2000/06/27 ----------------------- The major update with this version of track is the introduction of a smoothing filter. When atmospheric delay are estimated and/or there are unresolved bias parameters, the smoothed results represent the optimum solution to the kinematic problem. The smoothing filter is invoked using the BACK_TYPE SMOOTH command. The back_type BACK command still operates in the same way as version 1.02 i.e., when issued, the solution is run both forward and backward in time and both sets of results are included in the output files. RESTRICTIONS: The same number of ambiquities need to be used in the float and data_type selections, i.e., if LC is used for the float_type, LC or L1 or L2 needs to be used for the data_type. Specificially, in this case L1+L2 can not used. Other changes made include: --------------------------- (a) Reducing the amount of information printed about why bias flags are added; (b) Some addition output information, including estimated apriori coordinates if the aprioris in the batch file or rinex file seem bad; Output of final coordinates (grep for 'FINAL COORDINATES') when the process noise for Kinematic site is set to zero. When the SMOOTH option is used, the coordinates of these sites should not change in the output files. (c) Changed the FLOAT bias fixing algorithm and added two new arguments. Also increased the information printed about the FLOAT bias fixing so that users are better able to assess how to fine-tune the fixing. UPDATES TO TUNING PROGRAM ------------------------- The following suggestions are made to aid in tuning the program for specific applications. (a) The "cycle-slip" detector in track in the default settings is quite sensitive and in many cases overly sensitive so that it introduces bias flags that are not needed and often difficult to fix later. If many bias flags are added (as reported by the: Marking EX-WL slip at epoch 553 Site 2 PRN 03 Size -24.18 cycles Mask 26 lines), check the size of EX-WL slip. In this case it is large (24 cycles) and represents a true slip. Often however, the values are near the default limit of 0.2 cycles. The bias flags added due to these smaller slips can be removed by increasing the first argument of the ION_STAT command. Values as high as 0.4 cycles are often OK. The risk here is that an 1/1 L1/L2 cycle slip, will only change the EX-WL by 0.25 cycles and maybe missed with the larger tolerance. (b) Gaps in data: Often there are small gaps in data due to recording problems rather than loss of signal. The BF_SET command can be used to increase the allowable gap size from the default of 1 (i.e., all gaps are flagged) to a larger value. (c) For sites separated by more than 1 km, the FLOAT bias fixing algorithm is more efficient than the SEARCH algorithm especially if the LC observable is used. For these lines, the recommendation is to set: SEARCH_TYPE None FLOAT_TYPE 1 1 LC (See also expanded description of FLOAT_TYPE below). (d) Most GPS data seems to be generating FLOAT RMS scatters in the double differences of 20-25 mm. One of the reasons that value is large is because it is computed assuming kinematic positions and therefore the number of degrees of freedom at each epoch is reduced by 3 or 4 depending on whether or not the atmospheric delay is estimated. (d) If atmospheric delays are estimated and/or there are unresolved baises, it is strongly recommended that the SMOOTH option be used to obtain the best estimates of the station positions. (e) If multiple base-stations are needed, then the recommended procedure is the make all but the first base station kinematic but with zero process noise in the site_stats. The SMOOTH option should also be used. Of the F option is used, the coordinates of the fixed sites are assumed to be known to better than 1 mm. (f) As FLOAT biases are resolved, it recommended that the Average RMS fit be checked to make sure that it does not increase too much during the bias fixing. The format of the line is and can be extracted with a grep for 'Average RMS' For 20559 Double differences: Average RMS 21.57 mm End of Tuning -------------- Version 1.01 outputs information about the status of the run to the screen which is worthwhile saving and therefore it is recommended that the output be re-directed to a file. Basic program operation: ----------------------- Track has three main components in its analysis of kinematic data: (a) Rinex file reading and bias parameter assignment (b) Resolution of the biases to the correct integer values (c) Computation of the kinematic trajectory using the resolved values of the biases. The most time consuming step is (b) and the time taken for this part depends on the quality of the input data and the separations of the moving and fixed stations. Some of the user inputs in the command file will also effect the speed of this task. In Step (a), all the data to be processed in read into memory and biases are assigned to all data. A new bias is introduced whenever: (1) A satellite rises above the minimum elevation angle assigned by the user (default is 15 degrees) (2) There is a gap in the data of more than max_gap (default is 1) i.e., any missing data causes a new bias to be introduced (3) There is a jump in the computed ionospheric phase of more than max_ion_jmp. Default is 1.0 cycles. (Due to the ratio of the L2 to L1 frequencies, a 1-1 slip at L1 and L2 will change the ionospheric phase by 0.28 cycles). During step (a) reports will be issued about bias parameters being added, and why blocks of data are being removed from the analysis (usual reason is too small an interval of good data between bias flags). These reports look like: Marking EX-WL slip at epoch 553 Site 2 PRN 03 Size -24.18 cycles Mask 26 Marking EX-WL slip at epoch 554 Site 2 PRN 03 Size -23.93 cycles Mask 26 Marking EX-WL slip at epoch 555 Site 2 PRN 03 Size -24.13 cycles Mask 26 ... If the number of cycles is small (0.2-0.4 cycles) then the bias flag might not be needed. The first entry of the ION_STATS command controls the size of a jump flagged. Some kinematic data have gaps because of recording problems rather than cycles slips. If large numbers of bias flags are being added (typical behavior should be one per satellite per site), the BF_SET command can be used to increase the gap size that is automatically flagged. Once all the biases have been assigned, approximate estimates are found from the mean Melbourne-Wubbena (MW) wide lane (this is combination of range and phase that gives the difference between the L1 and L2 biases and it independent of the ionospheric delay and the geometry), and the mean of L1-(fL1/fL2)*L2 phase values (called the ionospheric phase or Extra-wide lane). The latter quantity is independent of geometry but will only equal zero when the ionospheric delay is zero. These mean values are computed using double differences. Some of the one-way bias values can be arbitarily set to zero when double differences are formed. The bias parameter table is output by the program and has the following format: BIAS FLAG REPORT: Type INITIAL . # Site PRN Start Stop Fixd L1 cycles L2 cycles DD Bias Refs Mean MW-WL +- Mean Ion +- INITIAL 1 1 PRN 05 1 6892 1 0.0 0.0 0 0 0 WL Res +- 0.000 0.000 0.000 0.000 INITIAL 2 1 PRN 06 1 6892 1 0.0 0.0 0 0 0 WL Res +- 0.000 0.000 0.000 0.000 INITIAL 3 1 PRN 17 1 6892 1 0.0 0.0 0 0 0 WL Res +- 0.000 0.000 0.000 0.000 INITIAL 4 1 PRN 10 1 6892 1 0.0 0.0 0 0 0 WL Res +- 0.000 0.000 0.000 0.000 INITIAL 5 1 PRN 24 1 6422 1 0.0 0.0 0 0 0 WL Res +- 0.000 0.000 0.000 0.000 INITIAL 6 1 PRN 30 1 6892 1 0.0 0.0 0 0 0 WL Res +- 0.000 0.000 0.000 0.000 INITIAL 7 1 PRN 15 3360 6892 1 0.0 0.0 0 0 0 WL Res +- 0.000 0.000 0.000 0.000 INITIAL 8 1 PRN 23 4103 6892 1 0.0 0.0 0 0 0 WL Res +- 0.000 0.000 0.000 0.000 INITIAL 9 1 PRN 26 4379 6892 1 0.0 0.0 0 0 0 WL Res +- 0.000 0.000 0.000 0.000 INITIAL 10 1 PRN 18 5232 6892 1 0.0 0.0 0 0 0 WL Res +- 0.000 0.000 0.000 0.000 INITIAL 11 2 PRN 05 1 6892 1 0.0 0.0 -1 0 0 WL Res +- 0.000 0.000 0.000 0.000 INITIAL 12 2 PRN 06 1 6892 1 -8200515.0 -3079519.0 11 2 1 WL Res +- -0.257 0.150 0.007 0.011 INITIAL 13 2 PRN 17 1 6892 1 -2305580.0 -1862667.0 12 3 2 WL Res +- -0.427 0.171 -0.137 0.014 INITIAL 14 2 PRN 10 1 6892 1 -8768807.0 -6842458.0 11 4 1 WL Res +- -0.200 0.130 -0.003 0.007 INITIAL 15 2 PRN 24 1 2453 1 5173625.0 4017810.0 11 5 1 WL Res +- 0.037 0.196 0.029 0.007 INITIAL 16 2 PRN 24 2493 5739 1 5173625.0 -3947627.0 11 5 1 WL Res +- 0.091 0.336 -0.006 0.027 INITIAL 17 2 PRN 24 5982 6421 1 5173625.0 -7378939.0 12 5 2 WL Res +- 0.133 1.531 -0.048 0.070 INITIAL 18 2 PRN 30 1 6892 1 -7074955.0 -5537433.0 11 6 1 WL Res +- -0.176 0.137 0.008 0.009 INITIAL 19 2 PRN 15 3360 6892 1 -6106087.0 -4838049.0 12 7 2 WL Res +- 0.371 0.384 0.004 0.028 INITIAL 20 2 PRN 23 4103 6892 1 -7242531.0 -5594566.0 12 8 2 WL Res +- -0.480 0.346 -0.111 0.021 INITIAL 21 2 PRN 26 4379 6892 1 -7464580.0 -5773140.0 12 9 2 WL Res +- 0.342 0.414 0.016 0.023 INITIAL 22 2 PRN 18 5232 6892 1 -8632784.0 -6768836.0 12 10 2 WL Res +- -0.400 0.688 -0.124 0.023 INITIAL The table gives a list of all bias parameters needed for the data being analyzed. The bias flag table is printed several times in the output. The different types of output of the table are: Type INITIAL -- This indicates that these are initial approximate estimates. UNIFIED -- This indicates that nearby bias parameters which have similar values have been assigned the value of the best approximate estimates. In the case above, the additional bias parameters are introduced due to data gaps (which are probably due to recording errors rather then loss of lock on the satellite since most of the values are nearly equal.) INPUT -- User input values when ambiguity file is passed through the command line or in the command file (see AMBIN_FILE below) FLOATXX -- where XX is a number. This is the output from the FLOAT resolution of the bias parameters. PASSXX -- where XX is a number. This is the output of the iterative fixing of the bias parameters to integer values. With each pass more bias parameters are fixed using the previously fixed ones. (The output of this part of the program is explained below). FINAL -- Final estimates of the bias parameters used in the kinematic trajectory determination. The columns in the Table are: 1 -- Bias parameter number. Runs sequentially from 1 to the number of bias parameters needed. 2 -- Site number (1 to number of sites) 3 -- PRN number of the satellite to which the bias parameter referrs. 4 and 5 -- Start and stop epoch numbers for the region where the bias parameter is needed. The epoch numbers are computed from the start time and increment by one for every epoch of data 6 -- Labelled 'Fixd': This column indicates the status of the bias flag. If the bias is fully resolved then the value will be 2 or 3 in the PASSXX and FINAL outputs of the bias flag table. A value of 1 means an approximate result fixed relative other defined biases, 0 means an approximate value that is estimate relative an another uncertain bias value (in double differences). 7 and 8 -- Estimates of the number of cycles needed at L1 and L2 9-11 -- Indicate the other bias parameters used in forming the double differences for this bias parameter. 0 0 or -1 0 indidates that this bias has been set to zero (All biases at station 1 are set this way, and at least one entry at the remaining stations can be arbitarily set this way. (The longest contiguous block of data is used as the criteria). 12-15 (Numerical column numbers). These are the estimates of residual errors in the Melbourne-Wubbena (MW) widelane and the Extra-wide lane and their expected sigmas based on a correlated noise model for the data (10-minute correlation time). The order is <MW WL> <Sigma> <EX WL> <Sigma>. The values and sigmas of these estimates plus the likely contribution of the ionospheric delay are used to compute the range of L1/L2 cycles to search over. Final column is the label for the type of report. Once the bias parameters have been established, track then, in a iterative loop, tries to fix the biases to the correct integer values. TRACK BIAS FIXING: ------------------ There are two bias fixing approaches used in TRACK: (a) Estimates of ambiguities from non-integer estimates called the FLOAT analysis; and (b) Estimated obtained by searching over ambiguity space looking for the best choices. Each iteration is composed of both types of algorithms although the FLOAT analysis can be skipped and delayed when it starts. FLOAT BIAS FIXING OUTPUT: ------------------------- By default, TRACK will first try to resolve bias using the floating point estimates of the biases. The estimated are reported as (this is for L1+L2, if LC then only one pair of Estimated Adjustments is given): Starting FLOAT iteration at 1 There are 1 kinematic sites in this analysis; 3 parameters per epoch to be estimated BF_FLOAT 12 4161 2 PRN 21 25 4157 1 Estimated Adjust. (m) 0.915 0.147 0.897 0.147 BF_FLOAT 13 5301 2 PRN 21 4220 5298 1 Estimated Adjust. (m) -0.964 0.135 -0.949 0.135 BF_FLOAT 11 12321 2 PRN 01 1 12320 1 Estimated Adjust. (m) 0.014 0.004 0.011 0.004 BF_FLOAT 17 20165 2 PRN 15 1 20162 1 Estimated Adjust. (m) 0.007 0.001 -0.001 0.001 BF_FLOAT 15 23689 2 PRN 25 1 23688 1 Estimated Adjust. (m) 0.028 0.001 0.026 0.001 BF_FLOAT 16 26326 2 PRN 14 87 26326 1 Estimated Adjust. (m) -0.020 0.001 -0.016 0.001 BF_FLOAT 18 26326 2 PRN 22 9720 26326 1 Estimated Adjust. (m) 0.000 0.001 -0.032 0.001 BF_FLOAT 19 26326 2 PRN 16 10002 26326 1 Estimated Adjust. (m) 0.012 0.002 0.034 0.002 BF_FLOAT 20 26326 2 PRN 18 17824 26326 1 Estimated Adjust. (m) 0.055 0.003 0.057 0.003 BF_FLOAT 21 26326 2 PRN 19 22632 26326 1 Estimated Adjust. (m) 0.046 0.004 0.042 0.004 where the first set of values refer to the bias parameters number and epoch at which it estimated (ie., the first entry above is for bias #12, for Site 2 PRN 21. It covers data between epoch 25 and 4157. At epoch 4161, its values were estimated to be 0.915 +- 0.147 m for L1, and 0.897 +- 0.147 m for L2 (if an LC search is used a single estimate LC will be shown). In this case, the biases correspond to 4.8 cycles (L1 wavelengh 190 mm), and 3.7 cycles (L2 wavelength 244 mm). The floating point estimates are then followed by the report of the attempt to fix them to integers. The case below is for LC (For L1+L2, there 2 pairs of estimated values). For 10692 Double differences: Average RMS 14.78 mm * BF S PRN Epoch Range F Estimate dLC Sig Limit Relative Rank Fix Fcode Change L1 L2 Residual L1 L2 Fits Best LC WL LG 61 2 PRN 04 1 913 1 -0.36 +- 7.90 SL 1.00 RR 0.00 F F SWRCO dL1,2 0 0 dL12 0.00 0.00 Fits 0.1 0.0 0.1 0.6 62 2 PRN 04 5551 5756 1 -0.02 +- 0.09 SL 1.00 RR 829351.09 F F ----O dL1,2 0 0 dL12 -0.03 0.05 Fits 0.0 0.0 0.0 0.1 63 2 PRN 09 1 416 1 -0.67 +- 10.46 SL 1.00 RR 0.00 F F SWRCO dL1,2 0 0 dL12 0.00 0.00 Fits 0.0 0.0 0.0 0.1 64 2 PRN 09 417 570 1 -0.46 +- 8.92 SL 1.00 RR 0.00 F F SWRCO dL1,2 0 0 dL12 0.00 0.00 Fits 0.0 0.0 0.0 0.1 66 2 PRN 09 1991 2398 1 -0.09 +- 5.49 SL 1.00 RR 0.00 F F SWRCO dL1,2 0 0 dL12 0.00 0.00 Fits 0.0 0.0 0.0 0.1 67 2 PRN 09 2403 2556 1 -0.56 +- 5.23 SL 1.00 RR 0.00 F F SWRCO dL1,2 0 0 dL12 0.00 0.00 Fits 0.0 0.0 0.0 0.1 69 2 PRN 09 5631 5756 1 -0.09 +- 0.30 SL 1.00 RR 2123.11 F F ----O dL1,2 0 0 dL12 -0.16 -0.07 Fits 0.2 0.2 0.0 0.6 ... 122 2 PRN 15 2205 3259 1 -0.52 +- 5.00 SL 1.00 RR 0.00 F F SWRCO dL1,2 0 0 dL12 0.00 0.00 Fits 0.7 0.2 0.0 8.9 125 2 PRN 31 2354 2672 1 -0.45 +- 5.23 SL 1.00 RR 0.00 F F SWRCO dL1,2 0 0 dL12 0.00 0.00 Fits 0.7 0.2 0.0 8.9 127 2 PRN 25 2683 3881 3 -0.02 +- 0.08 SL 1.00 RR 474848.16 T T ----- dL1,2 0 0 dL12 -0.03 -0.06 Fits 0.1 0.0 0.0 0.0 129 2 PRN 11 2785 3439 3 0.08 +- 0.12 SL 1.00 RR 99.81 T T ----- dL1,2 0 0 dL12 0.13 0.18 Fits 4.3 0.4 0.3 71.0 131 2 PRN 11 4837 5019 3 0.02 +- 0.06 SL 1.00 RR 3807.32 T T ----- dL1,2 0 0 dL12 0.04 0.07 Fits 0.8 0.1 0.0 13.6 139 2 PRN 27 4224 4380 3 -0.02 +- 0.07 SL 1.00 RR 59365.40 T T ----- dL1,2 0 0 dL12 -0.03 0.13 Fits 0.1 0.0 0.0 0.0 Here each bias is listed along with the estimates number of cycles and the Relative rank (RR) (ie. ratio of Best to second best choice increment in Chi**2 for fixing the bias); a pair of logical flags (T or F for True or False in fixing the bias), the change in the number of cycles and the difference between the integer and floating values of the baises. With version 1.06, the Fcode entries were added (see discussion at verision 1.06 entry in help) With version 1.03, additional information was added to this output. Specifically, the sigma following the +- must less than the SL (0.25 cycles in this case). For example: if Bias number 15 (site 2 PRN 24) had an acceptable RelRank, it would not have been fixed because the sigma is too large (the limit can be changed in the FLOAT_TYPE command, or the data noise can be reduced). In the case shown it does have sufficient relative rank (RR=253), but would not have been fixed because the "Best" fit value is 25.9 which is greater than the 25 tolerance set for this run. (In the next pass of the bias fixing this bias does get resolved). The "Residual L1 L2" columns are the differences between the floating point estimates of the number of cycles and the integerized values. The "Best" fit column (only for LC mode), gives the Fit quality for the best case. This value must be less than the tolerance (set in FLOAT_TYPE). For example, Bias 15 has a high RelRank, but was not fixed because the BestF value of 25.9 was above the default limit of 25. The "LC WL LG" columns are fits for the individual components used to compute the fit quality. The FLOAT_TYPE command allows the relative weights of these contributions to be changed. Specifically, LC is fit to the ionospheric free data, WL is the fit to an integer value for the MW Wide lane, and LG is the fit to the ionspheric delay. On longer baselines, this component should be downweighted (0.1 weight seems to work well for ~100km baselines). If the range data is not very good then downweighting the WL contribution can also be useful. Biases that are not fixed in the floating point analysis are then used in the search mode. The FLOAT_TYPE command allows specification of how the floating point analysis is done and at what iteration it starts. SEARCH BIAS FIXING OUTPUT: -------------------------- NOTE: Use of the SEARCH algorithm is no longer supported at all (Ver 1.23). The basic bias fixing loop outputs the following information (A "> " has been added to the start of the output lines. This symbol does not appear in the actual output). The first line is the ambiguity the program is nominally trying to resolve. In this case it is #11 which corresponds to Site 2 PRN 01 Epochs 1 10629. The step size in epochs is selected so that there are about 20 trials tested over the time range of the ambiguity. > Resolving Ambiguity # 11 Epoch Range 1 to 10629 Step 531 Pass 1 The following line is sometimes printed if there are less than 5 satellites visible at this time, > Not enough data for search at epoch 1 The following lines give information on what is being tested in the trial. At epoch 532, there are five biases which are not resolved (numbers 11, 15, 23, 25 and 26). For each of these biases, the number following the # sign is the number of integer values pairs to be tested (so for ambiguity 11, there are 3 values to be tested). The range of values searched depends on the uncertainty of MW and EX wide lanes and the magnitude of the expected ionospheric delay (the latter is based on the separation of the kinematic sites from the base station). The total search is the total number of trials to be carried out. There is a default limit of the maximum number of trials set at 1-million trials. > Epoch 532 5 Sets, Total Search 324. Ambiguities: 11 # 3 15 # 6 23 # 3 25 # 3 26 # 2 > Epoch 1063 5 Sets, Total Search 324. Ambiguities: 11 # 3 15 # 6 23 # 3 25 # 3 26 # 2 > Epoch 1594 5 Sets, Total Search 324. Ambiguities: 11 # 3 15 # 6 23 # 3 25 # 3 26 # 2 > Epoch 2125 5 Sets, Total Search 324. Ambiguities: 11 # 3 15 # 6 23 # 3 25 # 3 26 # 2 > Epoch 2656 5 Sets, Total Search 324. Ambiguities: 11 # 3 15 # 6 23 # 3 25 # 3 26 # 2 > Epoch 3187 5 Sets, Total Search 324. Ambiguities: 11 # 3 15 # 6 23 # 3 25 # 3 26 # 2 > Epoch 3718 5 Sets, Total Search 891. Ambiguities: 11 # 3 17 # 11 23 # 3 25 # 3 26 # 3 > Epoch 4249 5 Sets, Total Search 2565. Ambiguities: 11 # 5 19 # 19 23 # 3 25 # 3 26 # 3 ... More epochs showing the ambiguities being searched. ---- > Epoch 10621 6 Sets, Total Search 1215. Ambiguities: 11 # 5 23 # 3 25 # 3 26 # 3 28 # 3 29 # 3 Based on the trial ambiguities, the values are ranked based on the Sum of the inverse of the RMS phase fit squared (The Sum 1/Var column) and the sum of the inverse of the RMS fit of ionospheric delay estimate (on short baselines the RMS of the ionosphere is expected to be small). The RelRank columns give the ratio of the best fit to all other ranked entries. The # nn L1 L2 colums give the number of cycle changes at L1 and L2 corresponding to each of the ranked values. The Occ column gives the number of times the specific combination of L1 and L2 biases changes appeared in the ranked list. (Ideally this value would be the same as the number of trials i.e., about 20. In the top ranked entry below it is only 6). The biases are fixed to the top ranked value if, by default, the RelRank of the second best choice is greater than 5.0) > Ranked 2 entries for 5 ambiguities > Occ Sum 1/Var RelRank Sum 1/ion RelRank # 11 L1 L2 # 15 L1 L2 # 23 L1 L2 # 25 L1 L2 # 26 L1 L2 # > 6 209738.50 1.00 1231.12 1.00 0 0 -4 -3 0 0 0 0 0 0 > 2 5811.56 36.09 152.77 8.06 -1 -1 -5 -4 0 0 -1 -1 0 0 In the case above the biases would be fixed to values shown. The ionospheric rank is not used directly in the ranking (although, by default, 10% of the ionospheric delay fit RMS is added to the residual RMS). The search passes are iterated until as many biases are fixed as possible. For those biases that can not be fixed, the values which give the highest rank are saved. In the version 1.00 of track, the kinematic trajectory is the computed for the different observables types selected by the user, adopting as fixed the final set of biases. Those parts of the trajectory where the biases were not fixed with certainity (1 or 0 in Fixd column) should be treated with caution. At the bottom of the help, suggestions are made as to how increase the yield for the number of biases fixed. TRACK COMMAND FILES: -------------------- General Rules: All commands start with at least one blank character. A non-blank in column 1 is treated as a comment. For some commands, the command name is given followed by lines which contain the information. This list of values should be terminated with at least one blank line. Commands can be given in any order with one exception. The OBS_FILE command must be the first command. Commands: --------- (The @ denotes at least one blank in the lines below). @ OBS_FILE @ Site RX_file Type @ Site RX_file Type Command gives the site 4-char codes and the corresponding rinex file name. The <Type> is set to F for a fixed site, and K for a kinematic site. e.g., obs_file bish bisha289.97o F t39a t391a289.97o K @ NAV_FILE <name> <SP3/NAV> Gives the name of the SP3 or NAV file with orbits and clock information (e.g., igs SP3 files). When processing 24-hours of data, SP3 files from the preceeding and postceeding days should be concatinated together (headers removed at the day boundaries). e.g., nav_file igs09274.sp3 SP3 (GAMIT program doy can be used to get GPS week and day number from calender date). If NAV is used as the type then a broadcast ephemeris file is used. The above two commands are the only two strictly needed by track. The remaining commands are optional (although some are needed to get absolute results). @ MODE <Type> The MODE command allows the setting of defaults for the type of data being processed. These setting can then be overwritten if desired by use of the commands below. Three default setting modes are supported for <Type>: AIR -- Assumed to be high-sample rate aircraft. Sets the search_type to L1+L2, and allows gaps of 4-epochs, and minimum data of 120 epochs (1 minute for 2Hz data). SHORT -- Short baseline static data (<1 km). Sets search and analysis type to L1+L2 and minimum data of 20 epochs (10 minutes of 30 second sampled data). Data is still processed as kinematic data. LONG -- Long baseline static data (>1 km). Sets search and analysis type to LC and mininum data of 20 epochs. Atmospheric delay estimation is turned on with 0.1 m apriori sigma, and process noise variance of 1.d-6 m**2/epoch (~1 mm changes every 30 seconds for 30 second sampled data which accumulates to +-5 cm in a day). These settings are the same as atm_stats 0.1 0.001 @ SITE_POS @ Site <X (m)> <Y (m)> <Z (m)> Gives the apriori coordinates of the sites (based on 4 character name). If this command is not used, the coordinates from the rinex file are used. (If these are grossly in error then this can cause problems). e.g. site_pos bisa -2411875.6155 -4466436.9286 3850994.9249 t39a -2411530.1132 -4466700.4852 3850905.9740 @ REF_NEU <X (m)> <Y (m)> <Z (m)> Set the the XYZ coordintes of the point relative to which NEU offsets are computed. Default is the coordinates of the first site in the obs_file list. @ TIME_UNIT <epoch/sec/min/hour/day> Sets the time unit for process noise. Choices are epoch (default), seconds, minutes hour or day. Interval command must be used to specify sampling interval before this command is used. (Even when the interval is given in the rinex files). @ SITE_STATS @ Site <Apriori Sigma in XYZ> <RW noise in XYZ> Gives statistics to assign to the kinematic station positions. The <Apriori Sigma in XYZ> are the three sigmas in XYZ for the initial postion and <RW noise in XYZ> are the three sigmas in XYZ for the change in position between epochs of data. Since the motion of the kinematic sites is modeled as random walk (RW), the sigma of the change in position grows as the sqrt(number of epochs) Ver 1.21 and later: RW noise is sigmas (m)/sqrt(time unit) where time_unit command is used to set time unit. ALL can be used for the station name and the same statistics will be applied to all kinematic sites (NOTE: the fixed site do not change position). e.g. site_stats all 20 20 20 20 20 20 (20 meters apriori sigmas and changes of 20 meters between epochs). Feature 1.24: Added POST as entry after the Apriori sigma values, to allow specification aposteroi sigma for position at the end of the data span. @ TIMEDEP_PROCNS @ Site Sig XYZ (m/sqrt(t)) Start YY MM DD MN Sec End YY MM DD MN Sec Allows time dependent process noise to be added the statistics of a site or to all sites. The noise sigmas are addeded (in a variance sense) to the noise processes specified in the SITE_STATS command. Note only the random walk process noise is changed. @ ATM_STATS @ Site <Apriori Zenith delay sigma> <RW noise in Zenith delay> [<RW dH/dt noise> or SCALE] Gives the statistics for the atmospheric delays by site. The values are the initial sigma in meters, RW changes in meters per epoch and (added verion 1.2) a dH/dt variance term so that during rapid height changes more process noise can be added to zenith delay estimate. If SCALE is used instead of the numeric dH/dt term, then and atmospheric scale factor (proportional to height difference from the base station (first in obs_file list) is estimated. The output files contain the estimates of the atmospheric delay that is the scale factor is multiplied by the height difference to yield the estimate and its uncertainty. When SCALE is used then an offset in the atmospheric delay should be estimated at the base station since any delay difference will be zero with the SCALE model if the base and plane start at the same height. If the plane and base station are very close to each other at the start of the flight then this offset would probably not be needed. (SCALE added version 1.26). The process noise variance is (<RW dH/dt noise)*abs(dh/dt)>^2 per epoch where dh/dt is m/s. Typical value is 0.00023 e.g., atm_stats t39a 0.1 0.0003 0.00023 Set the apriori sigma as 10cm and allows the delay to change 0.3 mm every epoch (for 1Hz data, this lead to 18 mm noise in 1hr) and 2.3 mm per epoch when height is changing at 10 m/s (fast ascent or desent) @ ATM_BIAS @ Site <Atmospheric delay offset (m)> Allows adjustment to the apriori atmospheric delay model. Value is added to the nominal delay. In track Version 1.0, only a single offset applied to all epochs can be specified. Command is most appropriate for static sites separated by more than 20 km. @ ATM_FILE <File name> Allows the speficiation of file containing total atmospheric delay estimates at each site. The file format is the same as that obtained by grep'ing on 'ATM_ZEN X' in the o-file from a gamit run. @ USE_GPTGMF <Relative humidity (0-1)> Set the used of the GPT temperature pressure model and the GPT dry and wet mapping functions. Optional relative humity added vers 1.27; default 0.00. Use 0.50 for GAMIT compatabilty. Default is the older MTT atmospheric model. @ ANTE_OFF @ Command modified Version 1.14 @ Site <ARP dN (m)> <ARP dE (m)> <ARP dU (m)> <Antenna Name> <rcv code> Gives the antenna monument to Antenna Reference Point (ARP) offset in North, East and Up and name of site antenna (maybe unique name for site to allow mutlipath model to be used. Antenna name is 20 characters long with spaces allowed. First part of antenna name should not be all numeric. With Ver 1.26, receiver correlation type (rcv code) could be included. Values are N,C or P and can found in the rcvant.dat file by grep'ing on the receeiver name, The antenna name should appear in the antmod_file files. e.g., ante_off t39a .0000 .0000 0.0000 AOAD/M_B NONE C C here denotes a cross-correlating receiver type. @ RCV_TYPE @ Site <Receiver code N/P/C> Specifies the type of data-code-bias (DCB) correction needed for the receiver. Code specifies the type of L1 and L2 ranges being measures. The choices are P -- Pcode, C -- C/A and N C/A with cross corelation for L2 range. The codes can be found in gamit/tables/rcvant.dat. These codes can also be given in the ante_off command. An up-to-date DCB_FILE command must be used to specify the DCB biases. The files are available from the MIT ftp site and update once per month. @ BF_SET <Max gap> <Min good> Allows specification of the maximum size of gap allowed in data before a bias flag is inserted, and the number of good data needed to allow data to be kept. The defaults are 1 and 20 (i.e., any gap is flagged and at least 20 good phase measurements are needed between bias flags other wise the data is deleted). @ DEBUG <Start EP> <End EP> Allows detailed output for debugging problems for the data between epoch numbers <Start EP> and <End EP>. Default is no output. @ DATA_NOISE <L1> <L2> <P1> <P2> <Elev Weight> [PRN] Allows specificiation of the noise in the L1 phase, L2 phase, P1 range and P2 range, and the weight given to elevation angle depepence (at ver 1.20); variance is scale by (1+(W/sin(el))^2) where W is the <Elev Weight>. These values affect the sigmas printed for the position determinations (Units: m for all, except weight) Optional: PRN may be added and noise assigned to that PRN (if non-PRN form is used, this will replace all PRN specific values so use the non-PRN first followed by specific PRN values @ DATA_TYPE <choice 1> <choice 2> ... Allows specification of data types to be used in generating position estimates. The choices are: L1 -- L1 only phase L2 -- L2 only phase LC -- Ionospheric delay corrected phase P1 -- L1 pseudo-range P2 -- L2 pseudo-range PC -- Ionospheric delay corrected pseudo-range. The data types may be combined in each of the choices, e.g., L1+L2 would use both L1 and L2 while assuming that the ionospheric delay is negligible. Example: data_type l1 l1+l2 lc+p1 @ OUT_SIG_LIMIT <sigma (m)> Sets the maximum sigma of a position estimate for it to be output. If pseudorange data types are used, the default value of 1 m needs to increased to 10-100 meters. (Note restriction on back_type smooth: Option can not be used with pseudoranges). @ RMS_EDIT_TOL <n-sigma limit> Controls postfit editing of data by removing data more than n-times the RMS scatter of the residuals (Default 3.0) @ EDIT_SSV <site> <prn #> <start time> <stop time> Allows specification of data to be deleted from the analysis. The <site> name should correspond to the name given in the OBS_FILE command. <prn #> is the numerical PRN number of the satellite to be deleted. The <start time> and <stop time> are given as year month day hour min second. e.g., edit_ssv t39a 13 1998 8 16 20 0 0.0 1998 8 16 20 10 5.00 would deleted data on PRN 13 between the times given. @ USR_ADDBF <site> <prn #> <time (ymdhms)> Allows user to add a bias file at site <site> for PRN <prn #> at time <time>. First valid measurement at or after time will be flags. @ USR_DELBF <site> <prn #> <time (ymdhms)> Allows user to delete a bias file at site <site> for PRN <prn #> at time <time>. The time must match within 50% of sampling interval. @ AMBIN_FILE <file name> Allows specification of file with ambiguity estimates and flags that are used instead of the values determined by the program. (This is the same file that can be specified in the command line for the program). Putting it in the command files allows a record to be kept of the specific file used. The ambin_file must coincide exactly with the biases parameter table expected by by track (i.e., it usually generated with a grep FINAL of the track screen output (assumed re-directed to a file). Most importantly, if this file is to used, the bf_set, edit_ssv, cut_off commands should not be changed from the run that generated the ambin_file. These files will probably not be usable by different versions of Track. @ ANTMOD_FILE <file name> Name of ANTEX file containing phase center models for satellites and stations. Code is dimensioned to all 1-deg zen, azimuth spacing for site to map phase variations. Command can be issued multiple times with later values replacing earlier ones. NOTE: Command MUST be used after obs_file and ante_off commands to ensure entries for antennas are read. @ DCB_FILE <file name> Set the name of the data-code-bias (DCB) file. This file is part of the GAMIT tables directory and should be updated regularly. It is used to remove biases in the Melbourne-Wubbena widelanes. The receiver type can be specified with the RCV_TYPE or ANTE_OFF commands. @ FLOAT_TYPE <Start> <Decimation> <Type> <Float sigma Limits(2)> <WL_Fact> <Ion_fact> <MAX_Fit> [RelRank] Allows specification of the floating point ambiquity limits. It is through this command that the bias fixing algorithm is controlled. The main factors to consider are the <WL_Fact> and <Ion_fact> values which default to 1 giving them equal weight with the fit of the LC data. (For L1+L2 float type, these entries are ignored). For long baselines (>20 km) the <Ion_fact> should be reduced to give less weight to the ionospheric delay constraint. For 100 km baselines, 0.1 seems to work well. With very good range data (ie., WL ambiquities all near integer values), this factor can be reduced. For noisy or systematic range data (can be tested with a P1,P2 or PC solution), the WL_fact may be reduced. <Start> is the iteration to start the floating point estimation (default is 1) <Decimation> is decimation level ie. how often should the data by sampled in making the estimate (default is 4) <Type> Data type to use for the estimate. Choices are L1+L2 or LC. Note: for LC ambiquity resolution, the MW-Widelanes need to be well determined so that the L1-L2 ambiquities can be resolved from these estimates <Float sigma Limits(2)> Limits in the standard deviation of the floating point estimate that allows it to be fixed to an integer value (cycles), and on the maximum sigma allowed even to attempt resolving biases (Two values are needed). The sigma of the estimate will depend on the data noise assumed and the decimation rate (defaults are 0.25 cycles and 0.5 cycles) <WL_Fact> weight to be given to deviation of MW-WL from zero. Default is 1 (ie., equal weight with LC residuals). Setting the value smaller will downlweight the contribution of the MW-WL <Ion_fact> weight to be given to deviation of the Ionospheric delay from zero. Default is 1 (i.e., ionospheric delay is assumed to be zero and given unit weighting in deterimining how well a set of integer ambiquities fit the data. On long baselines, value should be reduced. <MAX_Fit> Maximum value of (res/sig)**2 allowed for biases to be fixed. (Default 25). [RelRank] Relative rank for bias to be fixed (Same as amb_cycle <Relative Rank> (Added version 1.20) @ MIN_TOLS <min LC sig> <WL Tau> <Dynamic Tol> This command allows the specification of minimum values that used to be hardwired in track. Specifying -1 for value will retain the default. <min LC sig> is the minimum sigma to be assigned to the float estimate of the LC bias estimates (Default 0.01 cycles) <WL Tau> is the correlation time in seconds to be used in computing the sigma of the mean WL values. (Default 600 sec). <Dynamic Tol> RMS of initial PC position solution that will set a site to be dynamic. (Defualt 10 m). @ BACK_TYPE <string> Allows specification of the type of solution to run backwards in time. Current options are (vers 1.02) BACK -- Simply runs a standard KF backwards in time. Write both the forward and backwards solution to the output file. Options for vers =>1.03 SMOOTH -- runs a smoothing filter. Only the forward running epochs are written to the output file. @ AMB_CYCLE <Samples> <Relative Rank> <Max search> Allows specification of the parameters to be used in fixing the bias parameters to integers. The options are: <Samples> -- Number of samples to use. Default is 20. Making this value larger will slow the program down because more epochs will be tested <Relative Rank> -- Relative rank needed for a bias parameter to be marked as fixed. Default is 5.0. Smaller values will mean more biases are fixed---to small a value and they might not be fixed to the correct value. <Max search> -- Maximum number of values to search at any epoch. Default is 1million. Setting this value too small can mean certain biases are never searched over. A larger value can result in very long times. @ ION_STATS <Jump> <ION PPM> <ION Weight> <ION height> <ION spatial> Allows specification of the characteristics of the ionosphere. For all parameters a value less than zero will use the default. The parameters given are: <Jump> - Largest jump in the ion delay allowed before bias flag introduced. (The delay is L1 - (fL1/fL2)*L2 and therefore a 1/1 L1 L2 slips changes delay by 0.28 cycles. Default is 0.2 cycles. Units: cycles <ION PPM> - Parts-per-million expected for ion contribution. (Values between 1 and 10 are typical) <ION Weight> - Weight to be given to ion-delay residuals RMS in computing the RMS of trial search values. Default is 0.01 (ie., not highly weighted). For short baselines (<10km) with an LC search, a high weight is recommended (ie., 1) <ION height> - Height of ionosphere used in computing ion delay elevation angle dependence (default 350 km). Units: km <ION spatial> - Spatial correlation length to used. Larger values will allow less ionospheric delay differences between sites (default 300 km). Units: km @ POS_ROOT <string> Allows specification of the root part of the file names for the position output files. The file naming scheme generates file names of the following form: for pos_root = mert_229 the names are: mert_229.GEOD.tubi.L2 -- Kinematic site tubi, GEOD output, data L2 mert_229.GEOD.tubi.LC -- Kinematic site tubi, GEOD output, data LC mert_229.NEU.tubi.L2 -- Kinematic site tubi, NEU output, data L2 mert_229.NEU.tubi.LC -- Kinematic site tubi, NEU output, data LC @ RES_ROOT <string> Outpute the postfit residuals for the data type being processed. For res_root mert_229 then files names generated ar mert_229.tubi.PRNnn.LC for site tubi with LC data @ SUM_FILE <string> Outputs a summary file of the run including statistics of the postfit data residuals @ WLS_ROOT <string> Outputs the wide lanes corrected for cycle slips to files whose names start with <string> @ RWL_ROOT <string> Outputs the raw wide lanes not corrected for cycle slips to files whose names start with <string>. (These are the values track uses to flag cycle slips and add bais flags). @ IONEX_FILE <file name> Name of IGS standard format IONEX file to be used. In long baseline processing, these models should improve the mean and RMS scatter of the EX widelane (L1-scaled L2 difference). @ IONLOS_FILE <site name> <file name> Name of site (4-char code) and corresponding line of sight ionospheric delay file. Format of file is <epoch number> <prn> <los TEC in TECU>. Data lines start with at least one blank at start of line. The file must be consistant with the start time and data interval of the track run using the file. (These LOS files are generated from smoothing the L1-L2 phase differences in the dump files generated with output type DUMP. @ OUT_TYPE <string> Allows specification of the type of position outputs to be generated. There are two choices: GEOD -- Geodetic coordinates (Latitude, Longitude and height). This format is compatible with GITAR output NEU -- Local North, East and height differences between the first fixed site and the kinematic sites. North, East and Up are defined by triad of axes at the reference site. DHU -- Difference in NEU from the initial coordinates of a site. Differences are in mm. XYZ -- Cartesian XYZ coordinates DUMP -- Dump of L1/L2 phase and range residals along with azimuth and elevation angles. When a IONEX files is used, the tec in TECU and the latitude and longitude of the sub-ionospheric point are also given. Both types can be output in one run if both strings are given with no blanks separating them (e.g., geod+neu) @ CUT_OFF <min elevation angle> Allows specification of minimum elevation angle of data to be used in the solutions. Units: Degrees @ START_TIME <Year Month day hour min sec> Allows a specific start time to be specified. Normally the start time defaults to the first time with overlapping data between at least two sites. @ INTERVAL <seconds> Allows specification of sampling interval. Must be in integer multiple of actual sampling interval (Units: seconds) NOTE: When rinex files have different sampling the largest interval should be specified. I may also be necessary to give a start_time to have the epoch line up correct (**DISASTER** No matching data message). @ NUM_EPOCHS <number> Allows specification of number of epochs of data to process. Normally the number of epochs is choosen to run until the end of overlapping data. @ EXCLUDE_SVS <list of PRN numbers to be excluded> Excludes satellites from being processed. Useful when a satellite is not in an SP3 file or not available during the times there are data. Example: exclude_svs 26 22 13 @ STOPGO_MODE <Variance reduction> Command to set a stop/go mode that allows data to processed with small stochastic variations during intervals when a receiver is static. (On Trimble receivers this done by changing the receiver from ROVE mode to STATIC mode). The rinex records for the two modes are: | denotes start kinematic mode 04 1 12 17 33 25.0000000 2 2 0.000 COMMENT KINEMATIC MODE COMMENT ....... | denote start static mode. 04 1 12 17 50 10.0000000 3 1 STATIC MODE COMMENT By default if no extra argument is given, the variance during static mode 10^6 times less than the kinematic mode process noise set in the site_stats command. @ MWWL_JUMP <tol cycles> Sets the magnitude of a jump the MW widelane that will be flaged as a slip. (Default is 5 cycles). Increase this value to stop bias flags being added. STRATEGIES FOR USE OF PROGRAM ----------------------------- Depending on the nature of the data analyzed, track can often not resolve all the ambiguities in a single pass. Below are some suggested methods for resolving all of the ambiguties. Both the GEOD and NEU output files tell the user the number of unresolved ambiguities at each epoch of data. The start of the NEU output look like: * YY MM DD HR MIN Sec dNorth +- dEast +- dHeight +- RMS # Atm +- Fract DOY Epoch #BF NotF * (m) (m) (m) (m) (m) (m) (mm) DD (mm) (mm) 1999 8 16 0 5 30.000 -20056.7861 0.0130 125156.5258 0.0126 132.9964 0.0655 10.16 6 -41.73 25.57 228.003819444 11 14 0 ... 1999 8 16 0 31 30.000 -20056.8053 0.0099 125156.5439 0.0104 132.9933 0.0405 16.00 7 -41.18 9.39 228.021874995 63 16 2 ... The last two entries on each line are the number of ambiguities needed for the data being analyzed and the number that have not been fixed to integers. Any entries with the last value not equal zero should be treated with caution. Ideally, we want to resolve all biases. No resolved biases in the final processing are estimated during the run. Since Vers 1.01 is only a forward Kalman filter, the position estimates when the biases are first being estimated will be effected by the poorly determined bias at that time. As more data are added, the bias will be better determined and have less effect on the position estimate. The number of biases that can be fixed is effected by choices in the command file and can altered by editing the AMBIN_FILE. For short baselines (<10 km), the search_type is best choosen as L1+L2. With aircraft data that has stationary periods near the base station before and after the flight, one strategy which seems to work, is to first process with L1+L2. This should fix all the biases for satellites visible during the stationary periods. The ambiguities are extracted from this run (with a grep FINAL of the screen output). The program is then run with search_type LC and the ambin_file specified. The LC search often has enough biases already fixed, that it can resolve the remaining biases that arise during the flight. Allowing the atmospheric delay to be estimated, is usually a good way of detecting bias fixing problems in the flight data since any problems will cause the atmospheric delay to jump. When multiple bias flags are added due to gaps, some of the biases might not be directly resolvable (above the RelRank tolerances) and these can be forced to be fixed by changing the Fixd column in the ambin file. (The Fixd value is bit mapped and so all that is needed is for bit 2 to be set, i.e., 2,3,6,7,10 .. are all acceptable values. Users might want to us a value different from that generated by the program e.g. use 7 to denote a user fixed value). Care should be taken when setting a bias fixed. For nearby biases, sometime GPS receivers will have 1/1 slips (i.e., 1 L1 and 1 L2 cycle change). Such a slip does not change the MW-wide lane but will effect the ionospheric delay and geodetic solution. In some cases, after the ambiguity search no ranked list will be produced. This occurs when none of the values searched seems acceptable (i.e., the search range is too small). The search can be increased on each bias parameter by increasing the sigma values for the MW and EX widelanes (ie., the 2nd and 4th numerical values following the "WL Res +-" in the bias flag table. It can also be increased by increasing the ion_ppm value. For static sites on long baselines (>50 km), fixing the station coordinates to good apriori values can often be used to get better ranking in the LC search. This can be done by using site_stats 0.0001 0.0001 0.0001 1 1 1. In the way track does its searchs, the apriori sigma of 0.1 mm (in this case) would be used during the search, but in the final output the markov process noise of 1 m would be applied at each epoch (except the first). Once the ambiguities are resolved and an ambin file generated, the solution could be re-run with loose aprioris sigmas. Often on long baselines, the biases are not resolved with sufficient rank to be fixed, but on examination of the time series of the atmospheric delay estimates and position estimates, it is clear that the correct values have been found. Editing the ambin file to show these biases as fixed will often help resolved other biases. Increasing or decreasing the ion_ppm value in the ion_stats command, often will either expand the search enough to allow the correct ambiguities to be found, or decrease the search range so that only ambiguities that generate small ionospheric delays are found. If the maximum number of searchs allowed is exceeded, reducing the ion_ppm will often reduce this number (if the MW- and/or EX widelanes are very uncertain, this might not help). For static baselines with site separations of >50km, the differential atmospheric (ie., difference form the apriori atmospheric delay model) can be large due to water vapor. The ATM_BIAS command be used to compensate for this difference and this will often allow the biases to be fixed. (The value choosen can be based on the part of the data where the biases were fixed or on another geodetic analysis e.g. a standard gamit solution.) In static solution, differential atmospheric delays of 10 cm at zenith (38 cm at 15 deg --- equivalent to 2 cycles) are often seen. Final Advice: Good luck. With perfect data and no ionosphere this is easy.