Maps / GPS

GPS Technology

A GPS receiver needs information from satellites orbiting the earth, which tells the receiver where the satellites are. When you are traveling with your GPS-device is switched off for a certain distance (over 300km), the information will be out of date and the GPS has to reload the orbital information before it can calculate its position. This can take a few minutes. Most receivers allow you to enter an approximate position (the nearest city, for example) to help speed up the process. The same is true when the receiver is first used after a period of weeks: the almanac data showing the approximate positions of the satellites is out of date and it may take from a few minutes to get a fix.

No signal even with a clear view of the sky
Sometimes you get a poor or no GPS signal despite a clear view of the sky. The reason is that the GPS receiver is not locking into the satellites. The main cause is the receiver not receiving the signal from the satellites.

In this case you best take a look at your unit's satellite page, as it identifies the number of satellites it's receiving. The more satellites a GPS receiver can "see" the better the accuracy. Buildings, terrain or sometimes even dense foliage can block signal reception, causing position errors or possibly no position reading at all. Since the satellites are moving, often you will typically be able to get a fix after waiting a few minutes. Sometimes, turning the receiver off and on again will reset it and it will lock on.

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