For pinpoint GPS precision a Google API key is now required to mitigate the cost of the Google Services that this webpage relies on. For most users this is not required.

Sounds reasonable, how do I get one?

You need to apply for a API key for Google Maps Directions API.

Also, if you intend on using the elevation feature you must enable the Google Maps Elevation API for this key as well.

Congratulations, you can now use your API key.

Your key is kept completely private, never logged anywhere and all traffic is HTTPS encrypted.