How to Read Topographic Maps

Contours join points of equal elevation on land with reference to a mean level, usually taken as the mean sea level. The height of various geographical features like mountains or depths of the oceans and steepness of the slopes can be measured and represented effectively by topographic maps. Streams, buildings, vegetation, roads and boundaries are also shown on a topographic map. In short, a topographic map represents three-dimensional area on a flat piece of paper. You may know the way to a destination by consulting a conventional map but it may not represent the obstacles in the path. A topographic analysis might show a mountain blocking the way, in which case a straight line path cannot be taken.

The first step to read a topographical map is to look for the title. Usually, it is found on the top right hand corner of the map. It gives an idea about the exact feature that is being studied. There are certain numbers marked all over the map. These form the grid system which determine the exact location of the feature. Latitude is an angular measure relative to the Equator. The Equator is at 0 degrees latitude and all other distances are given either north or south of the equator, starting from 0 degree to 90 degrees north or south, which indicates the poles of the earth. Similarly, there is an imaginary line running from the northern tip to the southern tip called the Prime Meridian. It is at 0 degree longitude. All other longitudes are given either to the east or west with reference to this line. The longitude ranges from 0 to 180 degrees. The 180 degree line is also known as the International Date Line.

UTM is an acronym for Universal Transverse Mercator grid system. This system is commonly used for military purposes and surveys. Each grid represented on the map is identified by a zone number at the top and a letter at the bottom right hand side, called the zone designator. For example, a city can be located as 'number letter' (20 S) or (16 B) and so on. The actual distance between two points and the corresponding distance on the map is given by a map scale. The contour lines, as stated earlier, give the elevation. As you scan across the lines, you see a change in elevation whereas if you move along the contour lines you are tracing the places with the same height. In the same way, if the lines are spread far apart, they represent a relatively flat area and if the lines are close to each other, it is an indication of a steep surface.

Topological maps are always direction oriented such the upper side is the north direction, the south is the downward direction, the west is the left side and east is the right side. There are two more representations- the grid line and the magnetic line. The magnetic line represents the actual north or the direction in which the compass will point. The angle between the magnetic line and the grid line is printed on the map. Thus, geographical directions can also be located with the help of a topographical map. At the bottom of the map, there is a scale indicating ratio between the map distances and the actual distances. For example, 50000:1 may mean 50000 miles represented as 1cm on the map. The scale varies according to the size of the map and the actual distance to be represented.

Colors too, have a special significance in a topographic map. For example, a solid green represents forest cover, blue indicates a water body while the color pink may represent a dense urban area. More specifically, a solid blue color indicates a river, stream, or pond. Thin blue lines indicate permanent flowing streams while a dotted blue area indicates intermittent flow. Marshy areas are represented by white color and wetlands are represented by a blue horizontal line and several blue vertical lines across it.
Dark red color indicates primary highways, alternate red and white lines show secondary roads and single or double black lines show crude or roads not in the best condition.

This information may help you get started with reading topographic maps. Regular practice with different types of topographic maps, is the key to master this technique.