How do you choose the best contour interval for your survey project?

1 What is contour interval?

Contour interval is the vertical distance between two adjacent contour lines on a map. It indicates how steep or flat the terrain is, and how much elevation change occurs over a given horizontal distance. For example, if the contour interval is 10 meters, it means that each contour line is 10 meters higher or lower than the next one. The smaller the contour interval, the more detailed and accurate the map is, but also the more complex and crowded it becomes.

2 Why does contour interval matter?

Contour interval matters because it affects how well your map communicates the features and characteristics of the land. A good contour interval should balance clarity and precision, and suit the intended use and audience of your map. For instance, if you are mapping a large area with gentle slopes, you may want to use a larger contour interval to avoid cluttering the map with too many lines. On the other hand, if you are mapping a small area with steep cliffs, you may want to use a smaller contour interval to show the variations and details of the terrain.

3 How to determine the scale of your map?

One of the main factors that influences your choice of contour interval is the scale of your map. The scale is the ratio between the actual distance on the ground and the distance on the map. For example, if the scale is 1:10,000, it means that one centimeter on the map equals 10,000 centimeters or 100 meters on the ground. The scale determines how much detail you can show on your map, and how much distortion you can tolerate. Generally, the larger the scale, the smaller the contour interval, and vice versa.

4 How to consider the purpose and audience of your map?

Another important factor that affects your decision on contour interval is the purpose and audience of your map. You need to think about why you are making the map, and who will use it. For example, if you are making a map for a civil engineering project, you may need a high level of accuracy and detail, and therefore a small contour interval. However, if you are making a map for a recreational activity, such as hiking or biking, you may prefer a lower level of accuracy and detail, and therefore a larger contour interval.

5 How to use standard contour intervals?

A helpful way to choose a contour interval for your survey project is to use standard contour intervals that are commonly used by other land surveyors and map makers. These standard intervals are based on empirical and practical experience, and are designed to produce clear and consistent maps. For example, some common standard intervals are 1, 2, 5, 10, 20, 50, 100, 200, and 500 meters. You can select the one that best fits your scale, purpose, and audience, or adjust it slightly if necessary.

6 How to test and refine your contour interval?

The final step to choose the best contour interval for your survey project is to test and refine it. You can do this by creating a draft map with your chosen interval, and checking how well it represents the terrain and meets your objectives. You can also compare it with other maps of similar areas and scales, and see if there are any discrepancies or improvements. If you are not satisfied with the result, you can try a different interval, or modify the existing one, until you achieve the desired outcome.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?