GPS watches can be general purpose, or they can be used for specific activities. Surfers will choose a device with preloaded tide tables, while athletes will want a multi-sports watch that is water resistant and measures distance. Some fitness trackers and other sports watches already incorporate location information, but dedicated GPS watches offer a lot more and more accurate information. The atomic clocks in GPS satellites can determine exact location and time in three dimensions from the duration of the signal sent to the GPS device.
The line that separates GPS watches from smartwatches is blurring. Activity trackers, watches and other devices that incorporate smartphone notifications with GPS functionalities are not GPS watches per se, but offer the same type of functionalities such as GPS watches like step count, distance, calories burnt, and heart rate measurements.