TTFF is the time between switching a GPS device on and the moment it produces its first valid position reading. A vehicle tracker that takes 30 seconds to fix its position after ignition-on will miss the first part of every journey. A tracker with a hot start TTFF of 1 second is ready before the driver has moved out of the parking space.
Three TTFF categories reflect different levels of cached satellite data:
- Cold start – no stored data at all; device must download full satellite almanac from scratch: 24-60 seconds typical
- Warm start – almanac stored but ephemeris expired; moderate reacquisition: 10-30 seconds
- Hot start – recent ephemeris and time reference available; typically 1-3 seconds
- AGPS – downloads orbital data via cellular before attempting satellite lock, reducing cold start to approximately 5 seconds