Photogrammetry is the science of obtaining reliable information about physical objects through the process of recording, measuring, and interpreting photographic images. It allows the extraction of geometric information from photographs to create 3D models. There are two main types: aerial photogrammetry uses photographs taken from aircraft, while terrestrial photogrammetry uses ground-based photos. The fundamental principle is triangulation - by taking photos from different locations, lines of sight can be developed and the precise location of points can be determined through mathematical intersection of converging lines. Important applications of photogrammetry include topographic mapping, engineering and construction projects, archaeology, and military intelligence gathering.

1. Photogrammetry surveying
and it‘s important
Prepared by:
Roshan Rawal

2. Photogrammetric surveying:advance technology :
•The word Photogrammetry composed of the words photo, gram and metry which
mean light,calculation and measurement respectively ie. Measurement from
photo.
•It’s a art, science and technology of obtaining reliable information about physical
object, environment by means of photograph in order to primarily determine
geometric characteristics such as size, form and position of the object
•Photogrammetry gathers measurements and data about an object by
analyzing the change in position from two different images. It uses
things like perspective, advanced processing software and photo
analysis to get the job done.
•The photograph either taken from the air or from the station on the ground.
According to this photogrammetry classifying in two categories
1. Aerial photogrammetry :
2. Terrestrial photogrammetry:

3. • Aerial photogrammetry: photograph taken from by a camera mounted in an
aircraft flying over the area. Mapping of the terrestrial photography is the best
mapping procedure yet developed(advance technology) for large project and
invaluable for military intelligence.
• Vertical photography:
Angle between camera
axis and vertical line is
less than 3 degree.
• Oblique:more than 3
degree.
• Forward overlap:
between two image
• Lateral or side overlap:
overlap between
between imgae from
adjacent line of flight

4. 2. Terrestrial photogrammetry:
These images are taken from a fixed position on the ground with a camera’s axis
parallel to the Earth. Data about the camera’s position, such as its coordinates,
are collected at the time the photo is taken. The instruments used for terrestrial
photography are often theodolites, though regular cameras are sometimes used
as well. Terrestrial photogrammetry for surveying typically requires fewer
resources and skilled technicians to accomplish, but it may take longer to cover
a large portion of land.
The principle underlying the method of terrestrial photogrammetry is exactly similar to that
of plane table surveying, i.e. if the directions of same objects photographed from two
extremities of measured base are known, their position can be located by the intersection of
two rays to the same object. However, the difference between this and plane tabling is that
more details are at once obtained from the photographs and their subsequent plotting etc. is
done by the office while in plane tabling all the detailing is done in the field itself.

5. •Principle of streoscopy:
“if two overlapping air photograph containing the same object,taken from the
different Position are viewed through a stereoscope and under certain condition
corresponding object will fuse together and terrain appear in three dimension.
Stereoscopy: it is the production of the illusion of depth in a photograph,
movie, or other two-dimensional image by the presentation of a slightly
different image to each eye, which adds the first of these cues (stereopsis).
The two images are then combined in the brain to give the perception of
depth.
Streoscope( त्रि वमद शर्शि): a device by which two photographs of the same
object taken at slightly different angles are viewed together, creating an
impression of depth and solidity.
Greek roots, stereo, "solid or three-dimensional," and phone, "voice.
The fundamental principle used in 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.

6. •Triangulation is the principle used
by both photogrammetry and
theodolites to produce
3-dimensional point measurements.
By mathematically intersecting
converging lines in space, the
precise location of the point can be
determined. However, unlike
theodolites, photogrammetry can
measure multiple points at a time
with virtually no limit on the number
of simultaneously triangulated
points.
•triangulation is also the way your
two eyes work together to gauge
distance (called depth perception).

7. Method to
view
streoscope pair
• Crosss eyes view
• Anaglyphs

8. •However, aerial photogrammetry is often unable to show all the details of
the objects that were captured. For example, in the 3D models it is not
possible to show all the details of the buildings such as building interfaces
and facades. Therefore, a necessity for another technology is emerged to
merge with, such as close-range photogrammetry.
Close range photograph:
Close-range photogrammetry (CRP) is a special type of terrestrial
photogrammetry that used to collect data about the objects such as
lengths, size, shape, and position from two or more images taking from
different stations by using a digital camera mounted on the ground and
facing the object as shown in Figure

10. Importance of photogrammetry:
1. To create 3D model:(digital elevation model)
•three-dimensional representation of an object created by plotting individual
points in 3D space on the X, Y, and Z-axis. The points are connected by
geometric shapes, such as triangles, lines, or curved surfaces, to form the
model. The points are connected by geometric shapes, such as triangles,
lines, or curved surfaces, to form the model.

11. •The way photogrammetry works is it looks at photos of a subject taken from
two or more locations. It uses the different perspectives from the images,
along with the location data of where the images were taken, to triangulate
the locations of points on the subject.
•To get the best results of creating a 3D model with your drone, you need to
do two things. First, you need to make sure there is a 60 to 70 percent
overlap in your aerial photos. This helps the triangulation process be more
accurate and track the same points between images.
•The second thing you want to do is to make sure you capture photos of your
subject at different angles and altitudes. Typically you want to capture
straight down images from around 150-200 feet. Then you want to circle
your subject at a high altitude with a 30º degree angle, at a middle altitude
with around a 45º degree angle, and a lower altitude with a 70º degree angle

12. •You can create a 3D model by
hand using 3D modeling
software, by using an algorithm,
or by scanning a physical object.
You can use a variety of available
software applications to process
your images and create your
model.

13. •Autodesk 3ds Max

14. •Architecture and
engineering firms are
using 3D models to
create realistic and
detailed context models
for their buildings and
development projects.
Architects use these
context models to
present how their
finished project will look
and to present their
project to investors and
key stakeholders.
•
•

15. •Engineering
•Since photogrammetry is so dependent on accurate
measurements, it’s no surprise that one of the first
industries to adopt this technology is engineering. When
building complex structures, buildings, or other feats of
technology, everything needs to be as accurate as possible.
•By using photographs from drones, engineers are able to
evaluate a construction project on a step-by-step basis to
ensure everything runs smoothly. Another valuable way to
utilize this technology in this industry is to show clients and
construction workers perspective images. Thanks to 3D
renderings, it’s easier than ever to create in-progress visuals
or prospective results.

16. •Topographical Mapping –
•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
control.
• A final field check is necessary

17. •Earthwork volume estimation:

18. •Calculation of catchment area:

19. •Town and city planning:

20. Road and railway enginneering: an extremely important advanatage of
photogrammetry is that road surveys can be done without closing lanea, disturbing
traffic. Once the road is photographed, measurement of road feature, including
elevation data, is done in the office, not field
•Study of geology of soil and crop patterns:
•Preliminary surveying:
•Town and country planning:
•Mining prospects
•Military intelligence:
World war ii gave rise to new development of aerial photography techniques.
•Water supply and power scheme
•Application in the department of transportation:

21. Advantages
• It can be used in locations that are
difficult,unsafe, or impossible to acess.
• It provide the broad view of the project area.
Identify the both topographic and cultural
feature.
• Aerial photogrammetry can provide information
of large area with very less time.
• )Information to the concerned authorities, public
etc can be easily conveyedthrough aerial
photograph
• aerial photogrammetry is the most popular in
architecture and land development because it
saves time and reduces cost during data
collection in comparison with fieldwork, which
may take days to complete work. It is also used
by the government for city planning and when
conducting environmental research.
Disadvantaged
• Can’t used in densely forest area.
• Costly for small area mapping.(highly
equipped and manpower and instrument
are used)
• Weather conditions affect the aerial
photograph.
• Also seasonal conditions affect. Snow
cover will give a false ground
impression.(November through march is
best for aerial photograph)

22. •Scale of photograph:
Scale= photo distance between two point/ real distance between two
point =focal length /distace of aircraft from ground.[using similar triangle
properties]

24. Thank you!