Re: [Gpsbabel-misc] Signal to noise ratio

[Robert L. <rob...@gp...>]

You're right. SNR is uncommon.  If you're pitstopping the data through GPX,
you'll certainly lose it.   When you're indoors, under a bridge, etc. you
should see spikes in HDOP and VDOP (horizontal/vertical dilution of
precision) and that's more likely to be preserved across formats.  We don't
really have a place for a "raw" SNR value in the data structure that's
shared between all the readers and writers, so we really can't do much with
SNR.

However, there may be an easier way to get it.  This is completely weird in
GPSBabel-land and I'd noticed it during code review, i'd probably have
removed it.  There is a 'csv' option in the mtk *reader* that bizarrely
*writes* a csv file that is apparently what the provided app uses.

http://www.gpsbabel.org/htmldoc-development/fmt_mtk.html#fmt_mtk_o_csv for
use.

There is code that looks like it's writing SNR.  See
https://code.google.com/p/gpsbabel/source/browse/trunk/gpsbabel/mtk_logger.cc?r=4941#923
 The writer is even unit tested somewhat so it's not totally broken, but
the test data that we have doesn't have SNR data as one of the columns.

This is such a weird wart in GPSBabel that I can't say if it works or
anybody but the original author has ever tried it, but if it plays out,
that's probably a winning lottery ticket for you.

RJL

On Fri, Apr 10, 2015 at 7:28 AM, Robert Luben <ro...@sr...> wrote:

> I am using GPSBabel (Version 1.5.2 under Linux) to extract data from
> QStarz BT_Q1000XT GPS as part of a research study. The GPS comes with its
> own Windows based interactive software but since we have lots GPSs to
> download and initialize, using GPSBabel in a shell script is the most
> efficient and quickest method. The current method is a two stage process -
> first downloading to .gpx format and later converting to .csv using
> iblue_757.style XCSV Style
> (
> https://code.google.com/p/gpsbabel/source/browse/trunk/gpsbabel/style/iblue757.style
> ).
> This works fine except that the variable SNR (signal to noise ratio) is
> missing. I guess SNR isn't a very commonly used variable but it we use it
> to give an indication of whether the GPS is being worn inside a building.
> SNR should appear in the SAT INFO section with multiple SNRs for each
> record.  However in iblue_757.style the SAT INFO section has "IFIELD
> IGNORE".  SNR is definitely recorded by the machine since the proprietary
> software is able to extract it to .csv.
>
> Does anyone know how it might be possible to capture SNR using gpsbabel or
> suggest some other way we can capture SNR within a script?
>
> Robert
>
>
>
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