9. Why do I get a GPS fix faster some days than others?
I. The constellation of GPS satellites orbit the earth in set patterns but the orbits are not geo-stationary. (Satellites are not always over the same point on the earth.) The orbits are such that there is more extensive coverage over the lower latitudes and less near the poles. Based on satellite position, your geographic location and heading you could experience the following phenomena:
- You may get fixes more easily/quickly at certain times of the day. For instance, at 10 AM more satellites will be visible in one part of the sky than will be visible at 3 PM in the same part of the sky. So at 10 AM you might get a fix in under a minute but at 3 PM you may not get a fix at all because only 2 satellites are visible.
Note: Buildings block any GPS signal so setting up in a vertical window immediately blocks at least 50% of the sky. Trees can interfere as well.)
- You may get fixes much better out of a window facing South than a window facing North. Again, this has to do with where the satellites are in the overhead sky.
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GPS Tips:
- If you want to see if you get a fix do it outside away from buildings and trees as best you can.
- CoPilot seeds the GPS receiver with a location and date and time. This is critical for getting a faster fix. If the date and time are wrong on your PDA and you are using it to get a fix with CoPilot, fix the date and time.
- Tap on Start, Settings, System, Clock and make sure the Date and Time are set correctly.
- Make sure the nearby city is within 50 miles or so of your location.
- In a car the window is generally tilted so that you have a greater view of the sky. You are more likely to get a fix in your car than in an office window. However, with the original GPS jacket the antenna is fixed to the plastic housing so if the unit is hung on a vent clip that is under the dash board overhang, the dash board is interfering and it is not likely to get a good fix.
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