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Download WhitepaperElevation Models
An elevation model is a digital representation of the earth’s terrain. A digital elevation model (DEM) is an important component of many geospatial projects, particularly for engineering, energy and academic studies. A DEM is created with stereoscopic data, similar to how a 3D movie is made. Let us help you source the raw data necessary for an elevation model that satisfies both your monetary and geospatial project constraints.
Depending on the desired outcomes of your project, the earth’s surface can be represented in two manners:
- As a digital surface model (DSM) which includes surface features such as vegetation and human-made structures.
- As a digital terrain model (DTM) whereby the surface features in a DSM have been removed so that it represents bare earth.
Our Elevation Products
The table below summarizes the key specifications of the elevation models we offer. These DEM products have been chosen from a variety of commercial offerings for their superior quality, competitive prices and global coverage.
| Product Name | Post Spacing (Resolution) |
Vertical Accuracy (LE90) | DSM or DTM? |
|---|---|---|---|
| Elevation30 | 20 to 30 m | 10 to 20 m | DSM |
| WorldDEM | 12 m | < 4 m | DSM + DTM |
| Elevation10 | 10 m | 5 to 10 m | DSM + DTM |
| WorldDEM Neo | 5 m | < 4 m | DSM + DTM |
| AW3D Standard | 2.5 and 5 m | 7 m | DSM + DTM |
| Advanced Elevation Series (AES) | 2 to 8 m | 2 to 8 m* | DSM + DTM |
| Custom DEM | Up to 2 m | Up to 1 m* | DSM + DTM |
| Elevation1/4/8 | 1 to 8 m | 1.5 to 2 m* | DSM + DTM |
| Precision 3D (formerly Vricon DSM/DTM) | 50 cm and 5 m | < 3 m | DSM + DTM |
| HxGN DSM | 40 cm, 80 cm and 5 m | 2X nominal stereo GSD | DSM |
* Vertical accuracies assume the use of ground control points during DEM production.
Deliverables
What can you expect to receive when you purchase elevation models? Elevation models can generally be delivered in two formats:
- As a raster grid where each pixel has a known footprint on the ground (e.g., 1 m by 1 m) with an associated elevation (e.g., 525 m). This delivery format is far more common.
- As a vector file with continuous lines, or contours, at known increments (e.g., spaced apart every 5 m) with an associated elevation (e.g., 110 m).
Useful information on terms used here
Circular & Linear Error
Circular error 90% (CE90) is the distance within which 90% of the points in the elevation model fall from their actual location in a horizontal or XY direction. Linear error 90% (LE90) is measured the same as is CE90 only it assesses vertical (Z) accuracy.
Ground Control Points
Ground control points are locations that are visible in the imagery used to create your elevation model with a known latitude, longitude and elevation. They should have an accuracy equal to the pixel size of the input dataset or better. We prefer to use points with an accuracy that is at least half the pixel size.
Contour Interval
We suggest extracting contours with a contour interval equal to a 4:1 or 5:1 ratio of the vertical accuracy. For example, a DEM with a vertical accuracy of 1 m LE90 should have contours with a 4 or 5 meter interval. An interval smaller than this represents over interpolated data. Another reliable estimate of the maximum contour interval possible is the relative vertical accuracy of the elevation model.
DEM Quality
While there are a variety of factors that control the final quality of a digital elevation model, here are several key factors: (1) the slope of the terrain – i.e. higher slopes can lower the accuracy; (2) the resolution of the raw stereo data – i.e. higher resolution can increase the accuracy; (3) ground control and breaklines – i.e. use of them improves accuracy; and (4) base to height ratio of the stereo pair – i.e. the suggested range is 0.25 to 0.8.
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