Jdipiet:
The instructions help you calibrate your AW1 without GPS to measure distances using your iPhone with GPS.
excerpt:
Calibrate your Apple Watch
While wearing your Apple Watch, go to a flat, open outdoor area that offers good GPS reception and clear skies.
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.
Open the Workout app. To start, tap Outdoor Walk or Outdoor Run. To set a goal before starting, tap the ... icon.
Walk or run at your normal pace for about 20 minutes.
Calibrating your Apple Watch for improved Workout and Activity accuracy - Apple Support