Faisal Khan(On leave)
Instructor :Engr. AfedUllah Khan
The science of obtaining information about an object
by acquiring data with a device which is not in direct
contact with that object.
photo = "picture“, grammetry = "measurement“,
photogrammetry = “photo-measurement”
Photogrammetry is the science or art of
obtaining reliable measurements by means
using photographs taken from the air or from space
with the camera usually pointing vertically
Vertical aerial photographs are taken along parallel passes called flight strips.
Successive photographs along a flight strip overlap is called end lap – 60%
Area of common coverage called stereoscopic overlap area.
called a stereopair.
(does not include horizon)
(1deg< angle < 3deg)
Position of camera at each exposure is called the exposure station.
Altitude of the camera at exposure time is called the flying height.
Lateral overlapping of adjacent flight strips is called a side lap (usually 30%).
Photographs of 2 or more side lapping strips used to cover an area is referred to
as a block of photos.
Radial line method :-
This method can be used if three points in each
photograph are known.
The first step is to determine the scale of the
This is obtained from the ratio of the distance
between two points on the photograph and the
distance between them on the ground.
Two points chosen for scaling should lie nearly
equidistant on either side of the principle point.
A map is drawn to this scale and all the ground
points are plotted on it
Terrestrial surveying is also referred to as field or
ground-based surveying. It can be defined as the art and
science of taking measurements on or near the surface
of the earth.
The terrestrial photographic surveying considered
as the further development of plane
The principle of this method is exactly similar to
that of plane table surveying
The position of an object with reference to the
base line is given by the intersection of rays drawn
to it from each end of the base line
The main difference between plane table and
terrestrial survey is
In plane tabling most of the work is executed in
the field while in terrestrial surveying it is done in
Field work of terrestrial photogrammetry consist
The preliminary vision or inspection of an area
to be surveyed.
The control is established by triangulation
All camera station should be connected by a
The elevation of the camera station should be
determined by the direct or trignometrical
The photographs are taken in pair from the end of
the base line such that a line joining the camera
station which is carefully measured
This method is the modern development of
It consists of taking stereoscopic views of the
surface features in pairs at the end of a base line.
The two exposures(photos) must be made with the
photographic plates in the same vertical plane.
This can be done by taking two photographs at 90
angle to the base line.
Horizontal distance between parallel principle is
usually between 30 meter and 120 meter.
Pixel is derived from the combination of two
words: Picture and element.
Pixel is the smallest building block of a picture. If
the resolution is high, the pixels are many than in
Vector images are made up of basic geometric
shapes such as points, lines and curves. The
relationship of the shapes is expressed as
a mathematical equation which allows the image
to scale up or down in size without losing quality.
Raster images are made up of a set grid of dots
called pixels where each pixel is assigned a color
value. Unlike a vector image, raster images are
resolution dependent. When you change the size
of a raster image, you shrink or stretch the pixels
themselves which can result in a significant loss of
clarity and very blurry image.
The plotting of map detail and contours is normally
carried out using aerial photogrammetric methods
These methods are used for both original survey and
revision, and replace classical ground methods except
where the task is so small that flying is uneconomical
The technique needs a certain amount of ground
surveyed control, but this requirement is being
continually reduced with the improvement of aerial
triangulation techniques to provide supplementary
A final Field check is necessary
Large Scale Plans
Large scale surveys can be produced accurately and
quickly by air survey methods, but require more field
checking in addition to the provision of ground control
For large tasks, such as road building and major
constructions, air survey methods are quicker and
cheaper than ground methods
Profiles for determination of earthwork quantities and
other data useful to Civil Engineer may be simply
obtained from the same photographs
c. Cadastral Plans
– Similar advantages may be gained by an air survey for
cadastral purpose as are provided in the production of
large scale plans.
– As the accuracy of the cadastral plan is related to the
value of land, the traditional ground method trends to be
slower, costly but very accurate
– In most cases, the accuracy of a well planned air survey is
sufficient for cadastral purposes, and this method is used
in many countries
– Where boundaries are related to described features, or
land is very valuable, the additional accuracy of ground
survey may be necessary
d. Land use maps
– Air survey techniques may be used not only to define the
extent of an area, but also to identify its use and measure
the yield of a crop
– Forestry is a typical application where, by plotting the
limits of timber and measuring tree heights, an accurate
estimate of yield may be given.
– The use of special films, such as color and infra-red will
provide additional information about the quality of the
e. Hydrographic Maps and Charts
◦ Air survey techniques are particularly valuable in the
accurate plotting of coastlines, sandbanks and small
islands where the changing tide is a problem for ground
◦ The use of special film will again add more information,
either by clearly delineating water limits or by extra
penetration in shallow water
f. Exploration and Reconnaissance
– Information may be gained about areas to which access is
restricted by employing air survey techniques
– In the case of military reconnaissance, a high flying or
unmanned aircraft can obtain photograph that will
provide data for an accurate survey
– For explorers, and area can be mapped before the first
entry, either from photographs obtained by aircraft as in
the case of Moon or Mars, or by specially equiped
g. Terrestrial, Industrial and Scientific Uses
– Photogrammetry has provided rapid, accurate and in
some cases unique solutions to many non topographical
– The following are of particular interest
Detailed Survey of Historic Buildings
Precise plans of building facades and architectural
detail may be obtained without direct measurement by
terrestrial photogrammetric techniques
2. Traffic Accidents
– Terrestrial methods are also used to record details of
accidents in some countries
– This allows obstructions to be cleared without delay, the
scene being plotted at a later stage
3. Medical Applications
– Short range photogrammetry is in use by doctors and
dentists to define conditions requiring treatment and
also to study the results of treatment
4. Analysis of movement
◦ Tidal and Particle movement may be analyzed by
photogrammetric methods by taking photographs of the
moving surface with a fixed camera
◦ The stereo model obtained shows vertical “relief”
proportional to the amount of movement “contours” may