Photogrammetric Surveying

 Photogrammetric Surveying

It is the branch of surveying in which maps are prepared from photographs taken from

ground or air stations. Photographs are also being used for interpretation of geology,

classification of soils, crops, etc. 

The art, science, and technology of obtaining reliable information about physical

objects and the environment through process of recording, measuring, and interpreting

photographic images and patterns of recorded radiant electromagnetic energy and

phenomenon.

Originally photogrammetry was considered as the science of analysing only

photographs. 

Advantages and Disadvantages: 

Some advantages of photogrammetry over conventional surveying and mapping methods are: 

 It provides a permanent photographic record of conditions that existed at the time the

aerial photographs were taken. Since this record has metric characteristics, it is not only

a pictorial record but also an accurate measurable record. 

 If information has to be re-surveyed or re-evaluated, it is not necessary to perform

expensive field work. The same photographs can be measured again and new

information can be compiled in a very timely fashion. Missing information, such as

inadequate offsets for cross sections, can be remedied easily. 

 It can provide a large mapped area so alternate line studies can be made with the same

data source can be performed more efficiently and economically then other

conventional methods. 

 It provides a broad view of the project area, identifying both topographic and cultural

features. 

 It can be used in locations that are difficult, unsafe, or impossible to access.

Photogrammetry is an ideal surveying method for toxic areas where field work may

compromise the safety of the surveying crew. 

 An extremely important advantage of photogrammetry is that road surveys can be done

without closing lanes, disturbing traffic or endangering the field crew. Once a road is

photographed, measurement of road features, including elevation data, is done in the

office, not in the field. 

 Intervisibility between points and unnecessary surveys to extend control to a remote

area of a project are not required. The coordinates of every point in the mapping area

can be determined with no extra effort or cost. 

 The aerial photographs can be used to convey or describe information to the public,

State and Federal agencies, and other divisions within the Department of

Transportation. 

Some disadvantages are: 

 Weather conditions (winds, clouds, haze etc.) affect the aerial photography process and

the quality of the images. 

 Seasonal conditions affect the aerial photographs, i.e., snow cover will obliterate the

targets and give a false ground impression. Therefore, there is only a short time

normally November through March, that is ideal for general purpose aerial

photography. A cleared construction site or a highway that is not obstructed by trees, is

less subjected to this restriction. These types of projects can be flown and photographed

during most of the year. 

 Hidden grounds caused by man-made objects, such as an overpass and a roof, cannot

be mapped with photogrammetry. Hidden ground problems can be caused  by tree

canopy, dense vegetation, or by rugged terrain with sharp slopes. The information

hidden from the camera must be mapped with other surveying methods. 

 The accuracy of the mapping contours and cross sections depends on flight height and

the accuracy of the field survey. 

History of Photogrammetry: 

1851: French officer Aime Laussedat develops the first photogrammetrical devices and

methods. He is seen as the initiator of photogrammetry. 

1858: The German architect A. Meydenbauer develops photogrammetrical techniques for

the documentation of buildings and installs the first photogrammetric institute in 1885 

(Royal Prussian Photogrammetric Institute). 

1885: The ancient ruins of Persepolis were the first archaeological object recorded

photogrammetrically. 

1889: The first German manual of photogrammetry was published by C. Koppe. 

1911: The Austrian Th. Scheimpflug finds a way to create rectified photographs. He is

considered as the initiator of aerial photogrammetry, since he was the first succeeding to 

apply the photogrammetrical principles to aerial photographs 

1913: The first congress of the ISP (International Society for Photogrammetry) was held

in Vienna. 

1980: Due to improvements in computer hardware and software, digital photogrammetry

is gaining more and more importance. 

1996: 83 years after its first conference, the ISPRS comes back to Vienna, the town,

where it was founded. 

Classification of Photogrammetry: 

Photogrammetry is divided into different categories according to the types of photographs or

sensing system used or the manner of their use as given below: 

I. On the basis of orientation of camera axis:  

a. Terrestrial or ground photogrammetry 

When the photographs are obtained from the ground station with camera axis horizontal

or nearly horizontal         

b. Aerial photogrammetry

If the photographs are obtained from an airborne vehicle. The photographs are 

called vertical if the camera axis is truly vertical or if the tilt of the camera axis is less

than 3 degree

. If tilt is more than (often given intentionally), the photographs are

called oblique photographs. 

II. On the basis of sensor system used:  

     Following names are popularly used to indicate type of sensor system used:  

 Radargrammetry: Radar sensor  

 X-ray photogrammetry: X-ray sensor  

 Hologrammetry: Holographs  

 Cine photogrammetry: motion pictures  

 Infrared or colour photogrammetry: infrared or colour photographs  

III. On the basis of principle of recreating geometry:  

When single photographs are used with the stereoscopic effect, if any, it is

called Monoscopic Photogrammetry.  

If two overlapping photographs are used to generate three dimensional view to create relief

model, it is called Stereo Photogrammetry. It is the most popular and widely used form of

photogrammetry.  

IV. On the basis of procedure involved for reducing the data from photographs: 

Three types of photogrammetry are possible under this classification:  

a. Instrumental or Analogue photogrammetry: It involves photogrammetric

instruments to carry out tasks.  

b. Semi-analytical or analytical: Analytical photogrammetry solves problems by

establishing mathematical relationship between coordinates on photographic image and

real world objects. Semi-analytical approach is hybrid approach using instrumental as

well analytical principles.  

c. Digital Photogrammetry or softcopy photogrammetry: It uses digital image

processing principle and analytical photogrammetry tools to carry out photogrammetric

operation on digital imagery.  

V. On the basis of platforms on which the sensor is mounted:

If the sensing system is space borne, it is called Space Photogrammetry, Satellite 

Photogrammetry or Extra-terrestrial Photogrammetry. Out of various types of the

photogrammetry, the most commonly used forms are Stereo Photogrammetry

utilizing a pair of vertical aerial photographs (stereo pair) or terrestrial photogrammetry

using a terrestrial stereo pair.   

Application of Photographic Survey: 

Photogrammetry has been used in several areas. The following description give an overview

of various applications areas of photogrammetry  

a. Geology: Structural geology, investigation of water resources, analysis of thermal patterns

on earth's surface, geomorphological studies including investigations of shore features.  

• Stratigraphic studies 

• General geologic applications 

• Study of luminescence phenomenon 

• Recording and analysis of catastrophic events

• Earthquakes, floods, and eruption.  

b. Forestry:  Timber inventories, cover maps, acreage studies 

c. Agriculture: Soil type, soil conservation, crop planting, crop disease, crop-acreage.

d. Design and construction: Data needed for site and route studies specifically for 

alternate schemes for photogrammetry. Used in design and construction of dams,

bridges, transmission lines.  

e. Planning of cities and highways: New highway locations, detailed design of

construction contracts, planning of civic improvements.  

f. Cadastre: Cadastral problems such as determination of land lines for assessment of

taxes. Large scale cadastral maps are prepared for reapportionment of land. 

g. Environmental Studies:

h. Land-use studies.

i. Urban area mapping.

j.  Exploration: To identify and zero down to areas for various exploratory jobs such as 

oil or mineral exploration. 

k. Military intelligence: Reconnaissance for deployment of forces, planning manoeuvres, 

assessing effects of operation, initiating problems related to topography, terrain

conditions or works.  

l. Medicine and surgery: Stereoscopic measurements on human body, X-ray

photogrammetry in location of foreign material in body and location and examinations

of fractures and grooves, biostereometrics.  

m. Mountains and hilly areas can be surveyed easily.

n. Miscellaneous 

Classification of Photographs:    

The following paragraphs give details of classification of photographs used in different

applications     

A. On the basis of the alignment of optical axis  

 Vertical: If optical axis of the camera is held in a vertical or nearly vertical position. 

 Tilted: An unintentional and unavoidable inclination of the optical axis from vertical

produces a tilted photograph.  

 Oblique: Photograph taken with the optical axis intentionally inclined to the vertical.

Following are different types of oblique photographs:  

i.  High oblique: Oblique which contains the apparent horizon of the earth. 

ii. Low oblique: Apparent horizon does not appear.  

iii. Trimetrogon: Combination of a vertical and two oblique photographs in which

the central photo is vertical and side ones are oblique. Mainly used for

reconnaissance. 

iv. Convergent: A pair of low obliques taken in sequence along a flight line in

such a manner that both the photographs cover essentially the same area with

their axes tilted at a fixed inclination from the vertical in opposite directions in

the direction of flight line so that the forward exposure of the first station forms

a stereo-pair with the backward exposure of the next station.