What Is Aerial Photogrammetry?
Aerial photogrammetry is not a very popular form of photography. Basically, aerial photogrammetry is a division of aerial photography. With aerial photogrammetry, you combine aerial photography shots to create 2D or 3D models. Specifically, cartographers will combine the aerial shots, as long as the shots feature at least two difference angles of the same general area. This guideline will go over the uses of aerial photogrammetry and how the photographs for photogrammetry are obtained.
Uses of Aerial Photogrammetry
Generally speaking, aerial photogrammetry is used to create topographical maps. Topographical maps are created so that both small and large geographical areas can be analyzed. In many cases, topographical maps are used in conjunction with geographic information systems. Topographical maps used to be created by hand, but there are now computer programs that can be used to create them.
Aerial photogrammetry is most popular in architecture and land development. It is very time consuming and costly to examine a very large portion of land by foot, which is why overhead shots are obtained. The government will also use aerial photogrammetry for city planning. When environmental research is being performed, aerial photogrammetry may be used to examine watersheds and deforestation research.
When 3D landscape models are being created, aerial photogrammetry is often unable to capture shots of the entire land area. In instances like these, aerial photogrammetry will be combined with other photographic technology that is able to capture photographs of the entire area. Examples of photographic technology that aerial photogrammetry might be combined with include white light digitizers, laser scanners, and LiDAR technology.
Why Are Multiple Shots Needed?
As previously mentioned, aerial photogrammetry requires at least two photographs that feature different angles of the same general location. To determine the estimated positions of objects that are in the photos, multiple angles of the same general location are needed. Aerial photogrammetry involves cartographers isolating the same objects in each photo. By isolating the same objects, cartographers are then able to triangulate the position of the objects. To compare multiple angles of the same general location, cartographers will typically use stereo plotters, which is a form of computer software.
How Are Aerial Shots Obtained?
With traditional aerial photography, photographers will simply take pictures from the window of an airplane or helicopter. That is generally not the case with aerial photogrammetry. Aerial photography is concerned with obtaining crystal clear photos of a particular object. Aerial photogrammetry is concerned with taking pictures of large portions of land.
Photographs for aerial photogrammetry are generally obtained by mounted digital cameras. Advanced digital cameras will be mounted to the bottom of an airplane and a person inside of the airplane will be controlling when the photographs are taken. If close-up shots are needed, the digital camera may be mounted to a remote controlled airplane. Due to flight patterns, airplanes are not able to fly too close to the ground. To obtain multiple shots from different angles of the same general location, the airplane will fly back and forth in different locations.