[teqc] two new intermittent problems with TPS data

Lou Estey lou at unavco.org
Fri Feb 6 09:43:31 MST 2009

Teqc users w/ Topcon TPS (and maybe also Javad JPS):

In the last three week, two new intermittent problems with
some TPS data have shown up:

1) The [RC] message for each epoch holds the L1 pseudoranges for
each SV in values of lightseconds, and typically these are less
than 0.1 lightsecond. Regardless, all these are passed through
a normalization function in teqc (used for all pseudorange values
in lightseconds, including TPS/JPS format) which tries to get
the values between 0 and 1 lightsecond -- because sometimes the
values are negative or greater than 1.  For the last 6 years of
reading TPS/JPS with teqc, there have been no problems with this
function, but now intermittent rogue values are now showing up
in [RC] messages, with values like 7.96170108643e+64,
-2.29339788867e+189, and 4.17034866919e+288 (actual cases!) --
so teqc appears to be in an infinite loop, but instead it is
very busy in loops subtracting or adding 1 lightsecond at a time
trying to get these values within the 0 to 1 lightsecond range.

I've added a test to the normalization function to toss out
pseudorange values where the absolute value exceeds 1e4 lightseconds.

2) The [SI] message for each epoch has an array holding an
identification for each tracked SV in that epoch, e.g. the PRN
for GPS SVs.  For the last 6 years of reading TPS/JPS with teqc,
each epoch with [SI] has always had a number of SVs greater than
zero, but now there has been at least one case where the [SI]
message occurs reporting zero SVs for an epoch.  If this occurs
with any previous builds of teqc, it will crash.  (The case
where this occurred the receiver was a HGGDT and the firmware
was "3.3 Jul,10,2008 p4".

I've added a test that skips epochs where [SI] reports zero SVs.

Both these fixes will be in the next teqc release -- which is
still waiting final vetting of reading the new Trimble record
which holds the GLONASS navigation message information.

If you are encountering either of these problems for time critical
TPS/JPS data when using teqc, please let me know, and send the
result of executing `teqc +version` so I can send you a
interim build of teqc.


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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