Subject: [NEXTEL-1] Best Practice for Writing World Class GPS Applications

From: [email-masked]
Date: Thu, 25 Sep 2003 22:33:05 -0400

-------- Original Message --------
From: Moya Reynaldo-ERM040 <[email-masked]>
Subject: Best Practice for Writing World Class GPS Applications

"How to Best Overcome Loss of GPS and iDEN Coverage"

The GPS receiver requires access to both the iDEN network and GPS satellite
signals to obtain rapid fixes. It is recommended that once the first fix is
obtained the application monitors the response codes and vary the times between
position requests accordingly. This recommendation is to handle the real world
case where an app requests fixes rapidly (less than 10 seconds apart) and then
loses network and GPS coverage (by entering a parking structure, basement, etc.)
The GPS system will continue to try to find the unit's position and will go into a
longer integration or acquisition mode that, once started, may take so long to
finish that it may miss GPS signals once back in coverage. The recommended
practice is to make fixes rapidly until a response code of FIX_NOT_ATTAINABLE or
FIX_NOT_ATTAIN_ASSIST_DATA_UNAV is returned several times in a row (for about 10
requests for delay=low and about 5 requests for delay = high). Once this scenario
occurs, then the app may wish to star!
 t the acquisition over from the beginning in anticipation that the phone might be
back in GPS coverage. To do so, the application must wait 15 to 20 seconds after
receiving the last response code before requesting a new fix. After this pause,
the application can continue requesting fixes at its normal.

iDEN Developer Support Team

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