look in the "official" fone book for your area and see if there is a set of maps in it somewhere.... in some areas those maps are taken from the county's gis office and the sectors are indicated as map squares.... if they aren't on those maps call courthouse and ask who handles the county mapping....the county where i work, for example, sells an atlas for about 30 bucks with the census tracts, sectors, girds, etc listed... and it is a really up-to-date map as well.... failing that make a trip to the sheriff's office and look on the wall.... maybe they have their coverage areas posted.