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FAQ: Does ArcGIS Mobile support differential GPS?

Question

Does ArcGIS Mobile support differential GPS?

Answer

Yes, both the ArcGIS Mobile application and the SDK runtime support real-time differential GPS (RT-DGPS). The GPS connection reads NMEA protocol, which contains positional information including the geographic coordinate and associated metadata that details the type and quality of the position. The majority of GPS devices in the market today support RT-DGPS using Satellite-based Augmentation Systems (SBAS), such as the North American Wide Area Augmentation System (WAAS) or the European Geostationary Navigation Overlay Service (EGNOS).

SBAS is a satellite system for delivering RT-DGPS corrections to each GPS receiver using the same signal as the existing GPS system. GPS receivers using these systems can increase their accuracy dramatically. To understand the expected accuracy of a particular GPS receiver, it is important to read the specification provided by the manufacture and also to run your own local tests to characterize performance in your environmental conditions.

The environmental condition impacts the expected accuracy in a specific location. This is a function of the GPS systems reliance on a weak radio signal that is influenced by a number of factors including the atmospheric conditions, regional topography, and local environment such as buildings and trees, which intercept or refract the GPS signals. What this means is that it is common for an RT-DGPS solution in tough environmental conditions to drop its connection.

For example, the Trimble GeoXT handheld can achieve submeter accuracy in real-time when using either WAAS or EGNOS. This accuracy is only available when the GPS receiver can view the WAAS or EGNOS satellites. These satellites are low elevation in orbit and hence, can often be blocked preventing guaranteed submeter accuracy.

In this situation, customers often expect to use the post-processed differential GPS (PP-DGPS) solution. ArcGIS Mobile does not currently support PP-DGPS.

Customers requiring a PP-DGPS solution should try using the GeoCollector for ArcPad, a hardware solution provided through the ESRI Hardware Solution's team and produced in conjunction with Trimble Mapping and GIS division.