Google Contacts using Lat and Long

I try to fill in ready made field with the Lat and Long inside Google Contacts to drive a map to a particular location (destination of a route). As I understand we can save coordinates of a contact. An example save the coordinates in the formattedAddress field of a gd:structuredPostalAddress and to use the format “lat,lon” (in decimal).

Which code can be used to fill in LAt and Long?