Postprocessed differential correction

avan_baelen — Mon, 23 Feb 2015 13:30:08 GMT

Last summer during our fieldwork in Africa our team collected a lot of GNSS measurements (format: .axf or .shp files, each with associated .ssf file) using ArcPad software installed on hand-held Trimbles (GeoExplorer 6000). Because we were working in a very remote area, we planned a postprocessed differential correction using data from a base station nearby. At the end of the campaign it turned out that the base station had unfortunately not been working properly, resulting in only a few days of base data being available.

Within the Trimble GPS Analyst extension for ArcGIS I successfully used the available base data to correct our GNSS measurements for these limited number of days. Particularly for the elevation these corrections make an important difference.

This, however, this still leaves me with a lot of uncorrected GNSS measurements which I would also like to correct (or at least get an idea of the vertical error). I tried downloading data from a different base station (located further away) available on http://www.unavco.org/, but the Trimble GPS Analyst extension is somehow not able to execute the corrections. After going through the whole differential correction procedure I get the end message: “100% total coverage; Selected 4827 positions for post-processing; Corrected 0 positions; Failed to correct 4827 positions” (no specific error type is mentioned).

A colleague suggested trying the differential corrections in Leica GeoOffice instead, but a conversion from .axf/.shp and .ssf files to a format compatible with the Leica software does not seem straightforward as I have not yet been able to find a conversion tool.

The only remaining option to somehow get a coarse estimate of the error of the currently uncorrected measurements would then probably be to develop some sort of algorithm.

I was therefore wondering

how I could find out why the differential correction with the unavco data is not working.
how I can convert .axf/.shp and .ssf files to a format compatible with the Leica software.
if anyone hase experience with developing such algorithms and how I would best proceed with this.

All suggestions are welcome! Thank you in advance!

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Postprocessed differential correction