There are many different reasons for gathering and understanding elevation data. Professionals in various fields rely on elevation data for developing water treatment services, water supply lines, highway construction, bridge locations, assessing environmental hazards, and even creating racecourses for marathons.
There are a few key terms to be familiar with in order to understand what you are seeing when you look at a topographical map.
- Elevation: In terms of land, this refers to the distance in relation to sea level. Where the ocean meets dry land is sea level; it is normally measured in feet.
- Contour lines: These invisible lines connect points of equal elevation to each other. They are essential to understanding elevation data. They show bands of elevation, as well as spot elevation on a map.
- Hachures: Hachures are marks pointing downwards and are found on contour lines. These marks indicate a depression in elevation. These depressions can be the result of erosion, meteor craters, or just naturally occurring dips in elevation.
- The first rule is sometimes called the rule of V's. They are usually found in stream valleys, with drainage channels passing through the point where the hachure is located.
- Another is often referred to as the rule of O's. The O's are closed loops that have higher elevations on the inside and head downhill on the outside. If the closed loops are craters or depressions, they are indicated by hachures.
- The third is the spacing of contours. If the contour lines are close together, this indicates a steep hill, and if they are far apart, it indicates a gentle slope.
Reading elevation data is not that difficult; so don't be afraid to try it. By following these simple tips you'd be surprised at your own elevation data reading skills.