Globalstar Product Management – Technical Support

Comparison of GPS with Globalstar Position Determination

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Question: I would like to know why my GPS unit does not agree with the position location information from the Globalstar phone.   In addition, I would like to use the Position Feature of my GSP1600 phone in conjunction with maps.  The latitude and longitude coordinates returned by my GSP1600 phone do not coincide with the latitude and longitude coordinates returned by my GPS receiver and I cannot seem to find a datum which matches the Globalstar results.  I assume the GSP1600 uses a different datum?  Which datum does it use and what are the correction factors to use with maps based on other published datums?

Answer: Globalstar was designed as a phone and data system, and not as a position location system.  Although Globalstar has the ability to determine position, the accuracy of a Globalstar position determination varies with time, as the user’s view of the satellite constellation changes.   The difference in Latitude/Longitude between datums is not nearly as great as the variation in accuracy of the Globalstar-determined position (2km to 10km) over time.   Therefore, when you notice differences between the Globalstar-determined position and a GPS device, the difference is undoubtedly due to the inherently higher accuracy of the GPS.  It has nothing to do with the datum(s) of the GPS.

The following article from the now-closed excellent site, Alaska Report  (alaskareport.com), describes a series of tests comparing the results of Globalstar MPD with GPS.

It is important to stress that the user should not rely on the Globalstar reported position as an absolutely accurate depiction of location.   The Globalstar Mobile Position Determination provides useful information, but it is not a position location service.   In all cases, the user will obtain a more accurate location from GPS than from Globalstar.

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Written by Joseph Crowley

September 19, 2008 at 10:06 am

Posted in Position Location

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