Yes, both the ArcGIS for Windows Mobile application and the runtime SDK support real-time differential GPS (RT-DGPS). The GPS connection reads NMEA protocol, which contains positional information (including the geographic coordinate), and associated metadata details the type and quality of the position. The majority of GPS devices on 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).
SBASs are satellite systems 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 manufacturer and also to run your own local tests to characterise performance in your environmental conditions.
Environmental conditions impact the expected accuracy in a specific location. This is a function of the GPS system's 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 at low elevation in orbit and can often be blocked, preventing guaranteed submeter accuracy. In this situation, customers often expect to use the postprocessed differential GPS (PP-DGPS) solution. ArcGIS for Windows Mobile supports PP-DGPS through Trimble Position post-processing software products. Customers requiring a PP-DGPS solution should consider using GeoCollector for ArcGIS for Windows Mobile, a hardware solution provided through the Esri hardware solutions team and produced in conjunction with Trimble Mapping and GIS division.