Positioning

GNSS devices often take a long time to get the first fix after first power-on or long power loss.

This is cold start. It is slow not because the module computes slowly, but because the receiver lacks prior information.

Positioning needs:

rough time
rough position
visible satellites
satellite orbit data
good enough signal quality

The more information is missing, the longer time to first fix becomes.

Cold Start Has Few Search Hints

If the receiver does not know roughly where it is or which satellites are visible, it must search a larger range of frequency, time, and satellite IDs.

Many devices with GPS fail indoors. Logs may show few satellites, no fix, jumping position, or a very long time to first fix.

This does not always mean the module is broken. GNSS signals are weak by nature.

GNSS positioning receives signals from multiple satellites and estimates distance and time error. By the time satellite signals reach the ground, they are already weak. Indoors, walls, floors, metal enclosures, the human body, coated glass, and installation direction attenuate them further.