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Derivative information
Examples of derived information
Digital terrain models contain more information than the altitude of the points. There is a lot of implicit information, which is not stored explicitly. It can be extracted using appropriate methods. Have a look at the following perspective illustration of a digital terrain model for the area around Türlersee (near Zürich, Switzerland). The following images illustrate the information which can be derived from digital terrain models.
The table below provides an overview of the information which can be derived from digital terrain models. To learn more about elevation, slope, plan curvature and profile curvature, have a look at unit 1.2. To learn more about intervisibility and the calculation of viewsheds, have a look at unit 1.3.
| Derivatives | Output type | Description |
|---|---|---|
| Slope | Number | Slope at a point |
| Gradient | Number | Gradient between two points |
| Aspect | Number | Orientation of the slope |
| Curvature | Number | Curvature in a certain direction (for example plan and profile curvature) |
| Intervisibility | Yes/no | specifies whether the viewer can see a certain point |
| Viewshed | Polygon | Area which is visible from one or more points |
| Hillshade | Image | Shaded relief under a given illumination angle |
| Stream networks | Line | Lines of water runoff in the terrain |
| Catchment | Polygon | Area where other areas drain in |
| Profile | Line | Change in elevation of a surface along a line |
| Volume | Number | Calculation of volume change between two surfaces |
| Perspective image | Image | Perspective relief representation |
| Line of greatest slope | Line | Path along the steepest slope |
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