gps_only API option

[mco...@cs.umass.edu]

In the API orders have a field named gps_only which is documented as "Bid on impressions with device-provided GPS coordinates only.". (I don't see a corresponding option in the UI).

I assume that this really means a location provided by an exchange?  Exchanges may be geolocating the IP address and not providing actual, high-accuracy device location API results.  Or is there something else going on?   

I ask because I am interested in targeting real, device provided GPS coordinates, but I believe that the lat/lon I am getting through macros and bidding are mostly IP translations (maxmind, ip2location, etc) and thus accurate only at say a "city" level. 

Through my own testing Mopub seems to provide the most accurate IP->GPS translations, but only when the "gps" macro is filled in.  When lat,lon is filled in, but not "gps", it seems to be inaccurate.  But this isn't really documented.

Any additional information around accurate GPS results would be helpful.