In addition to the latitude and longitude, a range is required for location information. The range (together with lat and lon) should describe a circle that just barely encloses the geopolitical entity (not the receivable range).
Also, if you are having to do some conversions to get lat and lon in that format, know that the actual administrative interface uses decimal lat and lon (i.e. 45.162306, -67.251389, xxx miles).
Also, if you know how the channel is used (i.e. Dispatch, tactical, talkaround, etc) that helps ensure that the channel will be properly selected based on service tag.