What is Photogrammetry?

The classical definition of Photogrammetry is the process of deriving metric information about an object through measurement made on the photograph of the object.

Photogrammetry is the science of making measurements from photographs. Photogrammetry means the measuring of features on a photograph.

This is concerned about metric or measurement aspect of the process. In addition to this photo interpretation aspect is also involved while the technology is used for mapping where feature collection is required.

The fundamental task of metric information is derived through establishing the geometric relationship between the image and the object as it existed at the time of the imaging. Once this is established other information of the object are derived.

Fundamental principle of Photogrammetry

The fundamental principle used by photogrammetry is triangulation.

By taking photographs from at least two different locations, so-called “lines of sight” can be developed from each camera to points on the object.

These lines of sight (sometimes called rays owing to their optical nature) are mathematically intersected to produce the 3-dimensional coordinates of the points of interest.

Triangulation is also the principle used by theodolites for coordinate measurement. If you are familiar with these instruments, you will find many similarities (and some differences) between photogrammetry and theodolites.

Even closer to home, triangulation is also the way your two eyes work together to gauge distance (called depth perception).