Time to first fix

Time to first fix (TTFF) is a measure of the time required for a GPS navigation device to acquire satellite signals and navigation data, and calculate a position solution (called a fix).

The TTFF is commonly broken down into three more specific scenarios, as defined in the GPS equipment guide: Many receivers can use as many as twelve channels simultaneously, allowing quicker fixes (especially in a cold case for the almanac download).

[1] Many cell phones reduce the time to first fix by using assisted GPS (A-GPS): they acquire almanac and ephemeris data over a fast network connection from the cell-phone operator rather than over the slow radio connection from the satellites.

The TTFFs for a cold start is typically between 2 and 4 minutes, a warm start is 45 seconds (or shorter), and a hot start is 22 seconds (or only a few seconds).

[2] In older hardware where satellite search is slower, a cold start may take more than the full 12.5 minutes.