Quote:
Originally Posted by dew.man
You can further verify this with the test apps by turning the radio off before running them - you will still get an approximation eventhough there is no connection to the towers.
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that makes no sense what so ever. ASSISTED gps means its using data (an IP address evident in the registry) so why would you turn off the radio? thatd leave you with ONLY gps satellites.
I do agree with the point about the warm/cold starts. And then people wonder why "omg it took 3 min for a lock!" Well thats within average for a cold start, even bluetooth SIRF III receivers take 1-2 min
"Cold Start- Time and position known to within some limits, almanac known, ephemeris unknown
Warm start- Time and position known to within some limits, almanac known, at least 3 SVs Ephemeris are known from previous operation.
The satellites (SVs) broadcast two types of data, Almanac and Ephemeris. Almanac data is course orbital parameters for all SVs. Each SV broadcasts Almanac data for ALL SVs. This Almanac data is not very precise and is considered valid for up to several months. Ephemeris data by comparison is very precise orbital and clock correction for each SV and is necessary for precise positioning. EACH SV broadcasts ONLY its own Ephemeris data. The validity of this data is dictated by the particular satellite and may be valid up to 4 to 6 hours. Each set of ephemeris data gives a "fit" indication which tells how long the particular Ephemeris data is valid. The Ephemeris data is broadcast by each SV every 30 seconds so GPS receivers have frequent opportunities to receive and log this essential information.
When the GPS is initially turned on after being off for a period, it "looks" for SVs based on where it "thinks" it is and based on the almanac and current time. With this information, appropriate SVs can be selected for initial search. When the GPS receiver initially locks onto a SV, the Garmin satellite display initially shows "hollow" signal strength bars. At this time, the Ephemeris data has yet to be completely collected (or any existing is "stale." Once the ephemeris data is collected from EACH SV in turn, the associated signal strength bar will turn "solid" black and then the data from that SV is considered valid and available for navigation."
http://gpsinformation.net/main/warmcold.htm