If a forest area is heavily wooded, or has other dense vegetation cover, it will not be possible to derive a DTM ground surface because the ground is not visible.

It should not be used for image orthorectification unless the source imagery is nadir looking, with no building or feature lean, to produce true orthoimages. The DSM is a valuable analytical dataset used for classifying features in orthoimages, such as discriminating asphalt pavement and asphalt roofs.

Digital surface model (DSM)-Digital elevation of the earth, including the elevation of objects on it such as trees and buildings.

The bare earth DTM dataset is used to produce the orthoimage and orthomosaics. This is also referred to as bare-earth elevation.

Digital terrain model (DTM)-Digital elevation of the earth, not including the elevation of any objects on it.

The 3D points generated from stereo pairs in the DEMs wizard are classified into two categories:

Thus, the DEM generation step is often not used, and existing USGS NED DEMs or SRTM DEMs, together with accurate GCPs, can produce Class I or Class II orthoimages at a scale of 1:5,000 or smaller.

These factors, together with accurate orientation information in the form of rational polynomial coefficients (RPCs), result in the condition that DEM accuracy and dense postings are less important in producing accurate orthoimages, as long as the adjusted exterior orientation and control points are adequate. Nadir (vertical) viewing, high-resolution satellite imagery is not affected much by distortion that is inherent in aerial imagery due to the large distance between sensor and ground, long sensor focal length (on the order of 10 meters), and small field of view.

Lost via domus 3d models rip