Hello Christopher,
Thank you for sharing your solution!
I have the same problem: The URL is working in a web browser but in ABAP I always get this error:
"Unable to authenticate the request. Provided 'signature' is not valid for the provided client ID, or the provided 'client' is not valid..."
I tried your solution (with set_header_field) and it worked. After that I debugged my program and changed the signature to "test" to have a look if I will get the error message from google. So I would be sure that the client and signature is passed correct. Unfortunately I don't get the error message instead I get the correct Geolocation.
If you call the webservice without the parameters client and signature you always get correct response messages. So I guess the http_client doesn't pass the "set_header_field" parameters correct to google. I also added the address parameter as a "set_header_field" and got a "ZERO_RESULTS" back.
I think your solution is working, but it doesn't send the client ID and signature to google...
Maybe someoneelse has any solution or experiance with that who wants to share this with us?
Best Regards
Markus