Photogrammetry and its Types

Photogrammetry is a technique for obtaining precise measurements and three-dimensional information from photographs. Photogrammetry is classified into numerous categories, each with its own set of applications and techniques. Here are some examples of common forms of photogrammetry:

1. Terrestrial Photogrammetry
2. Close range photogrammetry
3. Aerial Photogrammetry
4. Satellite Photogrammetry
5. Stereo Photogrammetry

1. Terrestrial Photogrammetry: It deals with the photograph taken from the ground surface as a platform from a device like a camera. It is used in applications like road design, building documentation, and the protection of cultural heritage.

2. Closed-range photogrammetry: If the distance between the object and the photographer is less than 300m then it is known as closed-range photogrammetry. It's commonly utilised in forensic analysis, archaeology, and engineering applications including measuring building dimensions and creating 3D models of archaeological sites.

3. Aerial Photogrammetry: It deals with the photograph taken from the air by mounting a camera on an aircraft. It may be vertical or oblique. Aerial photogrammetry is used for various purposes, such as mapping, land surveying, and topographic modelling.

4. Satellite Photogrammetry: Satellite photogrammetry is the processing of photographs taken by Earth-observing satellites. These satellites collect high-resolution pictures that can be used for landscape modelling, urban planning, disaster monitoring, and other purposes.

5. Stereo Photogrammetry: Stereo Photogrammetry deals with the overlapping of two or more photographs, obtained with a stereoscopic device. It is based on the parallax principle, which states that the shift in an object's position between two photographs is utilised for calculating its 3D coordinates. This method is necessary for terrain mapping and topographic analysis.