Tuesday, July 1, 2014

I keep hearing about Topographic Maps…..what are they?

This is a favorite subject of mine. Let's discuss what they are. Topographic maps are also commonly called contour maps or topo maps. The United States Geological Survey (USGS) took over responsibility for mapping the country in 1879 and has been the primary civilian mapping agency of the United States ever since. The best known USGS maps are the 1:24,000-scale topographic maps, also known as 7.5-minute quadrangles (1 unit on the map represents 24,000 units on the ground or 1 inch on the map represents 2,000 feet on the ground).  More than 55,000 7.5-minute maps were made to cover the 48 conterminous States. This is the only uniform map series that covers the entire area of the United States in considerable detail. 

Also it is worth noting that the green areas are forested and the white areas are open fields, pastures etc. Because many of the maps are 40 - 50 years old, what you find in the field (or on the ground) may be quite different. It is not unusual to find the white areas now covered in trees!!

A topographic map is a type of map characterized by large-scale detail and quantitative representation of relief, usually using contour lines. Contour line are lines on the map that connect all point with equal elevation above sea level. If you encounter a map where the contour lines are close together, that means that the relief is very steep. Traditional definitions require a topographic map to show both natural and man-made features.

Uses -  Topographic maps have multiple uses in the present day: any type of geographic planning or large-scale architecture; earth sciences and many other geographic disciplines; mining and other earth-based endeavours (such as planning and constructing ponds); and recreational uses such as hiking or, in particular, orienteering, which uses highly detailed maps in its standard requirements. Topo maps can be used determine % slope, potential pond site and other uses. A topo map can be used to determine the watershed area for a pond or potential pond. I use these extensively and here's how. I can draw a pond in on the map and my mapping program (Terrain Navigator Pro by MyTopo.com) will calculate the acres in the pond. Also, I will draw a polygon around the watershed area to determine how many acres drain into the proposed pond or lake site!


If you are dealing with LAND, your Realtor should provide you with a topographic map and an aerial photograph.... if not, you are not dealing with a Land Broker!!

For Information on Buying or Selling Land contact G. Kent Morris, ALC, RF at      (706) 457-0090