The U.S. Land Survey System is a way of dividing up land to describe locations. The Public Land Survey System (PLSS) is used in most states in the U.S. and is based on a grid system computed from survey records.
Unlike latitude and longitude, which measures points at the intersections of grid lines, the PLSS system describes squares in the grid. The grid starts with a baseline and a principal line of longitude in the region.
A township is a row of land generally six miles wide and measured as North or South of the baseline. Land in the seventh Township North is in row seven counting North of the baseline.
A range is a tier of land measured East or West from the line of longitude. Since a new range is measured approximately every six miles, it divides the Townships into six mile by six mile squares.
The township is further divided into one-mile sections and numbered from 1 through 36. The counting starts in the upper right hand corner, then continues to the left, drops down a row, and goes to the right, changing directions whenever it drops down a row. The numbers form a chain of land, snaking back and forth across the grid.
The United States Geological Survey (USGS) quarter quad system is a system of organizing squares of land into tiles on a map. As the USGS explains, "The USGS scans photos, almost exclusively from the National Aerial Photography Program (NAPP), an interagency effort coordinated by the USGS for map revision and a variety of other purposes. Each of these photos covers an area a little more than 5 miles on a side, representing about one-fourth of a standard, 7.5-minute USGS topographic quadrangle map. (Thus the occasional reference to quarter quad.)"
The Lake Region Classification System breaks Florida into 47 numbered lake regions grouped together based on similarities in physical geography, geology, chemistry, vegetation, climate, and other properties of surface water and soil. Lake management personnel use these regions to make comparisons among similar lakes and to predict effects of management techniques.
Each agency described above uses differing methods for collecting data.
Each agency described above uses various methods for calculating data.
The accuracy of location information is limited by data collection methods, classification system, and human error.