Template:FAQ/Questions/how fast should a

How long before satellites are tracked (and a fix is generated) using GPSstix?
Short Answer: You should have acquired some satellites within at least 41 seconds, but you must be tracking at least 3 satellites (with a good geometry in the sky) to generate a 2-D fix, and ...

The Start-Up (power-on) performance of the GPSstix depends upon several factors, as explained in the u-blox ANTARIS 4 GPS Modules System Integration Manual. The primary influences on GPSstix receiver start-up performance are:
 * Power - The GPSstix does not provide a separate back-up battery, so all almanac and ephemeris data is lost every time power is removed from the GPSstix. Consequently, all GPSstix start-up sequences are a "Cold Start", requiring up to 41 seconds for satellite acquisition (compared to <3.5 seconds for a Hot Start, when up-to-date almanac and ephemeris data is available).
 * Location, Location, Location - The u-blox LEA-4H SuperSense (weak-signal) algorithms are capable of acquiring and tracking the GPS satellite signals in very difficult situations (e.g., inside buildings and cars, under trees, in high-multipath environments like "urban canyons, etc.). However, a GPS receiver always performs best when the antenna has a clear, wide view of the sky - and LEA-4H Cold Start satellite acquisition requires 16dB more signal than satellite tracking does - so you will always get a fix faster if you acquire and start tracking satellites outside with a clear view of the sky, then move into more difficult reception areas.
 * Satellite Constellation - The more satellites in view, well above the horizon, and well-distributed around the sky, the faster the receiver will acquire the satellites and the more accurate the position fix will be. The receiver cannot generate a position fix until it is tracking at least 3 satellites (for a 2-D / latitude-longitude fix without altitude) or 4 or more satellites (for a 3-D / latitude-longitude-altitude fix), and the satellites must have a low-enough Dilution of Precision (DOP, the geometric relationship of the satellites in the sky) for the receiver to generate a valid fix.
 * Receiver Configuration - There are a number of control parameters that can be set (or mis-set ;) in the receiver to determine its behavior and performance.

The behavior, accuracy, and status of the receiver may change about 12.5 minutes after power on, as that is how long it generally takes to download a complete set of almanac data. For example, the almanac data contains:
 * Satellite (SV) Health - for each satellite. For example, the receiver may be tracking an "un-healthy" satellite until the almanac data for that satellite is received, in which case the receiver must then "throw out" the data for any satellites marked as not healthy.
 * UTC Time Offset - The receiver may be reporting GPS time (14 seconds ahead of UTC as of January 2007) until the almanac is received.