Photographic Surveying - Types & Uses

Types of Photographic Survey:

Photogrammetry may be divided into two classes.

• Terrestrial or ground photogrammetery.
• Aerial photogrammetry

1. Terrestial or Ground Photogrammetry:

In terrestrial photogrammetry maps are prepared from terrestrial (or ground) photographs or terrestrial photogrammetry employees take photographs from different points on the earth surface for measurement purposes.

The terrestrial photographic surveying considered as the further development of plane table surveying.

2. Aerial Photogrammetry:

In aerial photogrammetry maps are produced from air photographs (photographs taken form the air). Photogrammetry encompasses two major areas of specialization:

• Metrical
• Interpretive

The first area is of principal interest to surveyors since it is applied to determine distances, elevations, areas, volumes, cross-sections and to compile topographic maps form measurement made on photographs.

Interpretive photogrammetry involves objects from there photographic images and judging their significances. Critical factors considered in identifying objects of shape, sizes, patterns, shadow.

Uses of Photogrammetry:

Photography dates to 1839.

• Photogram try is used in preparing topographic maps, advantages include.
• Speed of coverage of an area
• Relatively low cost
• Ease of obtaining topographic details
• Reduce likely wood of omitting date due to tremendous amount of detail shown in photographs.
• It is used in land surveying to compute co-ordinates of section corner, body corner or pts of

Evidence that help locate these corners.

• Photogram try is used to make shore line in hydrographic surveying.
• It is used to preside ground co-ordinates of pts in control surveying.
• Used to develop maps and cross-section route (road or railways) and survey.
• Photogram try is also used successfully in many non-engineering fields’ e.g, geology, archeology, forestry, agriculture, conservation, military intelligence, traffic management accident investigation.
• It is particularly suitable for inaccessible regions, forbidden properties (restricted arrears) etc.

Photo Theodolite:

A photo theodolite is a form of ground camera. It is a combination of camera and theodolite and is used for taking photographs and measuring the angles which the plane of collimation makes with base line.

The optical axis of the camera is arrange parallel to the line of collimation of the telescope and the theodolite allows the determination of the orientation of the camera axis.

The angular measurement needed to fix the camera stations (A and B) during the control survey.