Apple Watch GPS is inaccurate.

Greetings, arnie98.

Start by calibration your Apple Watch:

"Check your settings

To make sure that your Apple Watch can get the information it needs, check these settings on your iPhone:

1. On your iPhone, open the Settings app.
2. Tap Privacy > Location Services. 
3. Make sure that Location Services is turned on.
4. Scroll down, then tap System Services. 
5. Make sure that Motion Calibration & Distance is turned on.
6. Continue with the steps below."

"Calibrate your Apple Watch

1. While wearing your Apple Watch, go to a flat, open outdoor area that offers good GPS reception and clear skies. 
2. If you have Apple Watch Series 2 or later, you just need your Apple Watch. If you have Apple Watch Series 1 or earlier, bring your iPhone for GPS. Hold your iPhone in your hand, or wear it on an armband or waistband.
3. Open the Workout app. To start, tap Outdoor Walk or Outdoor Run. To set a goal before starting, tap .
4. Walk or run at your normal pace for about 20 minutes.

If you don't have time to finish the workout, you can complete 20 minutes over multiple outdoor Workout sessions. If you work out at different speeds, you should also calibrate for 20 minutes at each of the speeds that you walk or run."

"Reset your calibration data

Here's how to reset your calibration data:

1. On your iPhone, open the Apple Watch app.
2. Tap the My Watch tab, then tap Privacy > Reset Fitness Calibration Data. " Calibrating your Apple Watch for improved Workout and Activity accuracy

If the issue continues, Contact Apple Support.

We hope this helps!

Sincerely.