If you use an Apple Watch paired with your iPhone, GPS distances on Apple Watch are based on the actual location of the iPhone to which it's paired. Make sure that both devices are within a 10-yard range to avoid pairing disruption.
However, if you have an Apple Watch Series 3 or above, you can now use the internal GPS of your watch. After starting a round on your iPhone, Hole19 will automatically appear on your Apple Watch and the first screen you'll see will be the ‘GPS source’ screen. This GPS screen will inform you what the source of your GPS is (iPhone or Watch), and how to change it. It’s easy! Long press the center of your watch screen to open up the Menu > Tap Settings > Toggle ON the switch if you want to use Watch GPS or toggle it off if you wish to use the GPS from your iPhone. If you choose the iPhone GPS, bear in mind that you should keep the iPhone in your pocket during the round.
Some considerations regarding Watch GPS and battery consumption:
Using the GPS from your Apple Watch heavily decreases the lifetime of your watch’s battery. From a full charge, you can expect an 18-hole round of golf to consume about 60% to 70% of the Apple Watch’s battery.
Closing (and not using) other Watch applications helps minimize battery consumption during your round. Click here for further tips on how to maximize battery life.
Although it's already possible to create independent apps with WatchOS 6, we are still considering what the best solution will be for the Hole19 App. For now, the App will still require the iPhone to work and you'll always need to start and finish the round on your iPhone.