Photogrammetry Survey

Photogrammetry survey or photogrammetric surveying is one of the branches of surveying. It is an art and the science of obtaining accurate measurements by using photographs taken from terrestrial or air stations.

In the photogrammetric survey, the objects are measured without being touched. The photographs are used for interpolation of geology, classification of soils, topographical maps, military intelligence, etc.

Principle of photogrammetry survey

The principle is very similar to that of plane table survey.

“If the direction of the same point photographs from two extremities of the measured base is known to their position can be located by the intersection of the two rays of the same object.”

The photographs are taken by means of a photo theodolite which is a combination of a camera and a theodolite.

Use of photogrammetry survey

1. It is used to conduct engineering surveys Suitable for hilly and mountainous terrain with little vegetation.
2. Used for geological mapping.
3. It provides accurate measurements therefore used for projects where high accuracy is required.
4. Used for interpolation of geology and classification of soil and crops.
5. Used for urban and regional planning.

Limitations of photogrammetry survey

1. It is highly expensive.
2. Unsuitable for a flatlands and dense forests.
3. Highly killed manpower is required.

Also Read: Hydrographic survey

Types of photographs used in photogrammetry

(A) Terrestrials photograph

The photographs taken from a camera station from at fixed point on or near the ground is called a terrestrial photograph.

(B) Aerial photographs

The photographs are taken from a camera station in the air with the axis of the camera is vertical or nearly vertical. Photographs are taken by a camera mounted in aircraft flying over the area. Mapping of large areas from an aerial photograph is photogrammetric and cheaper.

(C) Vertical photograph

In photogrammetric, the photo is taken from the air with the axis of camera vertical or nearly vertical. They are used for the compilation of engineering surveys on various scales.

(D) Oblique photograph

The photographs are taken from the air with the camera intentionally tilted from the vertical. It covers a large area of ground but far ends of photographs are not clearly visible.

Similar, type of article: Photogrammetry- Surveying

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