Hope you have managed to sort this, but if not then yes you can.
Go to the Google Maps app page in Splunkbase -- http://splunk-base.splunk.com/apps/22365/google-maps -- and scroll down to the section "Use existing geolocation information available in search results".
In my test events there are two fields, lat & long, which were renamed so the "geonormalize command will detect those fields and emit the _geo field".
sourcetype="test" | rename lat as gps_lat long as gps_lon | geonormalize
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