Use the URL:
https://heatmap-external-a.strava.com/tiles-auth/ACTIVITY/COLOR/{zoom}/{x}/{y}.png?Key-Pair-Id=MYVALUE&Policy=MYVALUE&Signature=MYVALUE
After logging in to https://www.strava.com/heatmap/ using a browser, you then have to retrieve and replace the MYVALUE items with appropriate cookie values for the following:
- CloudFront-Key-Pair-Id
- CloudFront-Policy
- CloudFront-Signature
Click on the padlock icon in the URL bar while at https://www.strava.com/heatmap/ and take the values from Cookies.
You can use also this Chrome extension to fill the fields:
https://github.com/zekefarwell/josm-strava-heatmap
