For projects requiring a more detailed look than can be offered by the common free sources of elevation data and for those in cloudy or hard-to-reach regions where this data is of poor quality, Astrium GEO’s Elevation10 product suite is the ideal solution. Elevation10 is a 10-meter digital elevation model (DEM) derived from stereo pairs collected by the radar satellite, TerraSAR-X. These DEMs are often delivered within a month of order placement utilizing data obtained in the past two years.
TerraSAR-X is a synthetic aperture radar (SAR) satellite, meaning it is an active sensor unlike the optical satellites most of us are familiar with such as QuickBird, Pleiades 1 and WorldView-2. An active sensor (1) creates an energy pulse, in this case radar waves; (2) aims them at a surface, in this case our planet; and then (3) very accurately measures the amount of time it takes for this pulse to return to the sensor. Radar waves can pass right through clouds which are an optical satellite’s worst nightmare.
As TerraSAR-X measures the time it takes for energy pulses to return to its sensors as well as its position in space in the XYZ directions, radar stereo pairs have higher accuracy than do traditional pairs collected by optical satellites. This means that elevation data extracted from TerraSAR-X stereo pairs is accurate even without the use of ground control points. Ground control points can be expensive to collect – particularly in remote and unsafe areas – so this can be a significant cost savings vis-à-vis other elevation products.
Elevation10 is created from TerraSAR-X radar stereo pairs collected in StripMap mode. StripMap data has resolution up to 3-meters with a footprint that is 30 kilometers (km) wide by 50 km long. By employing TerraSAR-X stereo pairs collected in both ascending and descending directions, Astrium GEO is able to remove many of the anomalies that are common in SAR elevation data.
Elevation10 is offered as both a digital surface model (DSM) which includes vegetation, buildings and other human-made structures; and as a digital terrain model (DTM) where these have been removed. DTMs are hydrographically enforced to make sure that features which impact water flow, such as dams and embankments, are represented. Hydrographic enforcement is also offered with DSMs. The accuracy specifications for Elevation10 are as follows:
- Absolute Horizontal Accuracy – 5 to 10 meters (Circular Error 90%, CE90)
- Absolute Vertical Accuracy – 5 to 10 meters (Linear Error 90%, LE90)
For regions of the world with limited access, such as the Himalayas and the Andes, or in regions with persistent cloud cover and/or haze, such as Malaysia and Beijing, Elevation10 is the ideal solution. Elevation10 data is priced by the square kilometer according to the product type with academic discounts available. For more information about Elevation10, contact your Apollo Mapping sales representative at (303) 993-3863 or [email protected].