GPS Tracking means a watch pulls signals from satellite constellations (GPS, GLONASS, Galileo, BeiDou, QZSS) either to record your position and route or to set the time automatically for wherever you are standing. There are really two flavors here. The first is location tracking for running, cycling and hiking, where the watch lays down a breadcrumb trail you can analyze afterward. The second is the GPS solar approach that Seiko launched with the Astron in 2012: light-powered movements that grab the correct time and time zone from orbit. Multi-band GNSS, which uses the L1 and L5 frequencies together, is the heart of accuracy because it rejects the confused signals that bounce off tall buildings and dense forest.
For real examples, the Garmin Forerunner 970 runs multi-band GNSS with SatIQ to pick the right satellite mix for the environment and sits around $750. The tougher Fenix 8 starts near $1,000, while the Enduro 3 stretches GPS tracking to roughly 320 hours on a charge with solar assist. On the solar side, the Garmin Instinct 3 Solar is $399 and holds 130 to 260 hours in GPS mode depending on size. The Apple Watch Ultra 3, from $799, uses L1+L5 dual-frequency precision GPS plus Backtrack to retrace your steps. For the time-sync camp, the Seiko Astron GPS Solar starts around $2,400 and the Citizen Attesa Satellite Wave GPS F950 (CC4104-53E) is roughly $1,995 and locks a signal in as little as three seconds.
When you are choosing, sort out what you actually need first. If you want route maps, navigation and training data, look at Garmin or Apple, and weigh battery life carefully, because the Ultra 3 gives you about 14 hours in a GPS workout while the Instinct 3 Solar goes for days. If you simply want the right time anywhere with no battery swaps and a classic analog face, a Seiko Astron or Citizen GPS solar makes more sense. Either way, favor models with multi-band GNSS; single-band GPS still drifts noticeably in a city.
One nuance worth keeping in mind: a GPS sport watch is really a small computer, and the software, map updates and ecosystem (Garmin Connect, Apple Health) are half the experience. A GPS solar watch stays closer to the simplicity of a mechanical piece, runs on light and never needs daily charging. What you trade away is the detailed route analysis and on-wrist mapping.