iSi provides a variety of satellite-based mapping services. Source files contain the layers needed for GIS applications and can be updated and maintained frequently.
A DEM (Digital Elevation Model) is used for Orthophoto production and other mapping applications.
Quality DEM products are measured by the precision of the elevation represented by each pixel and how accurately the morphology is captured. High-quality DEM-derived products are measured against several important parameters:
• Terrain roughness
• Sampling density (elevation data collection method)
• Grid resolution or pixel size
• Interpolation algorithm
• Vertical resolution
• Terrain analysis algorithm
A Stereo Pair is required for DEM production.
An Ortho-rectified satellite Image, used for mapping applications
An Orthophoto Product is produced from satellite image and a DEM. The DEM used is obtained in one of three ways;
• Produced by iSi (DEM required)
• Supplied by the customer
• iSi can use an existing Free-for-Commercial-Use DEM – the SRTM, which has a grid spacing of 90m.
Comprised of several Orthophoto Products together, for mapping applications