[teqc] change to qc plot file format for GNSS data

Lou Estey lou at unavco.org
Wed May 6 12:34:11 MDT 2009


For anyone that uses or is interested in teqc's qc ASCII plot files:

In the first serious overhaul of this part of the code in about 13 years,
the next version of teqc will have a slightly different plot file format
for GNSS data.  This will automatically kick into gear if the input data
is recognized by teqc as having data from SV constellations other than GPS,
or if you use a new "+plot2" option.

The new (still ASCII) format looks like (compare with the traditional plot
format described at http://ls.unavco.org/pipermail/teqc/2007/000566.html ):

COMPACT2
T_SAMP    30.0
START_TIME_MJD  54466.000347
13 G06 G07 G08 G09 G10 G15 G18 G21 G24 G29 G26 R07 R08
    0.000     0.000     0.000     0.000     0.000     0.000     0.000     0.000     0.000     0.000     0.000     0.000     0.000
14 G06 G07 G08 G09 G10 G15 G18 G21 G24 G29 G26 R07 R08 R23
   -0.124     0.494    -0.679     0.096    -0.016    -0.008    -0.062    -0.022     0.056     0.511    -0.022    -0.021    -0.138     0.000
14 G06 G07 G08 G09 G10 G15 G18 G21 G24 G29 G26 R06 R07 R08
   -0.489     0.234    -0.204     0.623     0.034     0.010     0.199     0.106    -0.030    -1.057     0.028     0.000    -0.031    -0.050
13 G06 G07 G08 G09 G10 G15 G18 G21 G24 G26 R06 R07 R08
   -0.177    -0.590    -0.345    -0.504    -0.421     0.017     0.239     0.086    -0.036    -0.048     0.119    -0.089     0.760
14 G06 G07 G08 G09 G10 G15 G18 G21 G24 G26 R06 R07 R08 R24
   -0.595    -0.209    -1.365    -1.391     0.198     0.075    -0.038    -0.089    -0.134    -0.011     0.012    -0.035    -0.590     0.000
-1
    0.426    -0.166     0.002     0.781    -0.041     0.039     0.131    -0.065    -0.030     0.024     0.119    -0.107    -0.724    -1.204
...

1st line: always says "COMPACT2"

2nd line: the time sample interval between epochs in seconds

3rd line: start time of first epoch in modified Julian days (note:
6.0 Jan 1980 is equivalent to the modified Julian day of 44244.0)

4th line: first epoch; the first number is the number of SVs for data at
this epoch, and the SV IDs afterward are the same as used in RINEX 2.11

5th line: data of first epoch for the N SVs; the units should be semi-obvious:
   mp1 and mp2: meters
   elevation and azimuth: degrees
   ion and iod: meters and meters/sec (I think)

following pairs of lines if the SV count is non-zero: same as 4th and 5th lines
for the following epochs, except a -1 for the number of SVs means the SV list
is the same as the previous epoch, unless:

if the epoch lines lists 0 SVs, then there is no following data line

Same tricky little detail: the format of each datum on the data lines is (in C):
"%8.3lf%c ".  The %c is sometimes used to output an non-space ASCII character
indicating some special attention to that SV at that epoch, such as a slip.

A few notes on both the traditional COMPACT and new GNSS COMPACT2:

* the missing data line if the SV number is zero also has and continues to
   apply to the traditional COMPACT format (just forgot to document that
   fact in the previous email)

* the start time in modified Julian days is now labeled "START_TIME_MJD"

* a bit of work has gone into making sure that you should now get the same
   plot files from different teqc builds using the same data, e.g. the use
   of "-1" for the SV count, the SV listing, the number of data points per
   epoch matching the number of SVs listed

* the only difference that has been noticed between the same nominal plot
   file from different teqc builds: the actual data may vary by +/- 0.001
   unit, though this is still vary rare but can ever occur between, say, Solaris
   Sparc (big endian processor) vs. Solaris x86 (little-endian processor).

cheers,
--lou

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Louis H. Estey, Ph.D.              office:  [+001] 303-381-7456
UNAVCO, 6350 Nautilus Drive           FAX:  [+001] 303-381-7451
Boulder, CO  80301-5554            e-mail:  lou  unavco.org
    WWW:  http://www.unavco.org   http://jules.unavco.org

"If the universe is the answer, what is the question?"
                                                -- Leon Lederman
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