What Are the Different Types of Photogrammetry Jobs?

Photogrammetry refers to the technique of measuring the shape, size, and spatial position of an object using a combination of a camera and a film. Since the invention of photography by Nipps and Dayle in 1839, photogrammetry has a history of more than 170 years.

Photogrammetry is the use of photos obtained by optical cameras, which are processed to obtain the shape, size, position, characteristics and interrelationships of the subject.

The main task of photogrammetry is to measure topographic maps of various scales, establish topographic databases, provide spatial basic data for various geographic information systems, land information systems, and various projects, while serving non-topographic fields such as industry , Architecture, biology, medicine, archeology and other fields. ^[1]

Invented by Nipps and Dayle in 1839

Although there are various types of photogrammetry, their basic theoretical basis is common, which is the mathematical model of photogrammetry. For a single image, this mathematical model is based on the three points of the object point, the lens center, and the image point being on the same straight line during the photography. The equation thus established is called the collinear condition equation or conformation equation. For a stereo image pair (two images taken by different photography stations with a certain image overlap), a mathematical model that can indicate the internal and external geometric relationship can be derived. In actual work, these mathematical models constitute The theoretical basis of single-image photogrammetry and dual-image (stereo) photogrammetry was introduced. ^[3]

The main features of photogrammetry are:

(1) Obtain subject information without touching the object itself.

(2) Reconstruct 3D objects from 2D images.

(3) Surface data collection method.

(4) Simultaneously extract the geometric and physical characteristics of the object.

Image acquisition methods include frame-type cameras, optical-machine scanners, panoramic cameras, CCD solid-state scanners, and synthetic aperture side-view radars. ^[5]

According to the distance, it is divided into space photogrammetry, aerial photogrammetry, ground photogrammetry, close-range photogrammetry, and microphotogrammetry.

It is divided into topographic photogrammetry and non-topographic photogrammetry according to use. Topographic photogrammetry is mainly used to map and map scientific and technical issues in the country's basic topographic industry, architecture, archeology, geological engineering, and biology and medicine.

According to the processing method, it is divided into analog photogrammetry, analytical photogrammetry and digital photogrammetry. The results of analog photogrammetry are directly drawn on the drawing table through mechanical or gear transmission, such as topographic maps or various thematic maps. They must be digitized before they can enter the computer; the results of analysis and digital photogrammetry are various forms of digital products and visual products. Digital products include digital maps, digital elevation models, digital orthophoto maps, survey databases, and geographic information systems. And land information systems. The visualization products here include topographic maps, thematic maps, vertical and horizontal section views, perspective views, orthophoto maps, electronic maps, and animated maps. ^[6]