Pharos Science & Applications 505 - Manual (Page 47)

Chapter 5: Additional Information
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Troubleshooting for GPS
Why does the Pocket PC keep accessing the map?
1. The CPU speed is related to the accessing speed of the storage card.
You are advised to use storage cards with better accessing speed.
2. Make sure that the RAM of the P ocket PC has free space over 20 MB for
the map program to work properly. (You are advised to stop all other
programs and run the map program only.)
Why is the navigation delayed? The vehicle has reached a
spot but the navigation arrives at the same spot 3~5
seconds later.
1. The reception function of the Pocket PC causes the difference.
2. The CPU speed and accessing speed of the storage card are not good
enough.
3. Make sure that the RAM of the Pocket PC has free space over 20MB for
the map program to work properly. (You are advised to stop all other
programs and run the map program only.)
4. The GPS signal is sent once per second, which may cause the
difference.
5. The Pocket PC is affected by the environment.
Why does the vehicle in the map drift?
1. The shifting signal happens a lot for GPS using the Xtrac technology
(most of the highly sensitive GPS systems use the Xtrac technology).
This technology performs positioning by magnifying and then computing
the weak signals. With the satellite signals that change constantly, GPS
keep computing to correct the difference. When the difference appears
obvious, a shifting signal happens. The map program receives GPS
signals and displays positioning signal on the screen. It is not about
shifting signals, but simply the positioning difference.
2. GPS satellite signals allow the difference of 5~25 meters. The design of
the phase lock loop of the map program may also be one of the factors.