A series of aerial photographs are taken and then used to create a stereoscopic image of the ground in a certain location.
Each photo must have several points of known XYZ coordinates identifiable in the photo.
These known points are used as the basis to create an accurate photographic model or digital terrain model of the subject area
Accurate horizontal and vertical information can then be obtained from the photos.
What are the advantages over traditional survey methods? Aerial mapping and aerial photography can have increased efficiency in gathering large amounts of information, especially on larger sites. There are potential drawbacks however. These include:
Features obscured by trees of other objects unidentifiable from aerial photos
The possibility of less precise, though not necessarily less accurate, information than that obtained by traditional survey methods.
It's important that all cameras meet National Aerial Photography Program (NAPP) specifications and are calibrated by the United States Geological Survey (USGS).
The Surveyor's Role
