7. Photo analyzing
Quantitative
That is size, length, shape, height, area etc.
Qualitative
Geology, vegetation, drainage, land use etc. This section is
primarily concerned with the quantitative evaluation of
survey photographs.
8. Types of Photogrammetry
• There are two types of photogrammetry as follows:
• Interpretative Photogrammetry.
• Metric Photogrammetry.
• Arial
• Terrestrial
9. Classification of Aerial
Photographs
Vertical Photograph
An aerial photograph taken with the optical axis of the camera held in a
vertical or nearly vertical position is classified as vertical photograph
Tilted Photograph
In practice, the camera axis is nearly held vertical. But due to
unavoidable aircraft tilts the camera axis is unintentionally tilted from
the vertical. Then the resulting photograph is called tilted photograph.
10. Oblique photograph
An oblique photograph in which the apparent horizon appears
is termed as high oblique photograph.
Apparent horizon
It is the line in which the earth appears to meet the sky as
visible from a point.
11. Low oblique photograph:
It is one on which the apparent horizon does not appear. A pair of low
oblique taken in sequence along a flight direction in such a manner that
both photographs cover basically the same area is called convergent
photographs.
12. Interpretative Photogrammetry
• Interpretative photogrammetry involves recognizing and
identifying objects and judging their significance through
careful and systematic analysis from photographic images.
Metric Photogrammetry
• It consists of making precise measurements on photographs
and other information to determine relative locations of
points.
13. Requirements of Photogrammetry
Technology rafay
Overlapping image for stereo view required for 3D vewing and
measurement.
Ground Control Points (XYZ) for establishing positional
relationship between photo and ground.
Stereo Pair Photograph
Green Dots showing GCP’s
14. Applications of
Photogrammetry
To prepare plan metric topographical maps (Surveying/mapping).
To determine the space position of ground objects.
For acquisition of military intelligence (Military/artificial intelligence).
To classify soil (Forestry/agriculture).
For the interpretation of geology (Geology/archaeology).
Assessment of crop damage due to floods or other natural calamities.
To prepare a composite picture of ground.
To relocate existing property boundaries.
16. 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.
17. 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.
Indivisibility 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.
18. Scale
Scale is the ratio of the size of any object or feature
or area within the photo to its actual size .
A large scale image will cover a smaller area but will
show ground features in more data .
Scale =
𝑃ℎ𝑜𝑡𝑜 𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒
𝐺𝑟𝑜𝑢𝑛𝑑 𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒
19. Calculating Scale
Feature of Known Size
One method is to use a feature of a known size in the photograph to calculate the
scale.
(e.g. football field or standard event field)
20. Feature of Known Size
• Example: You measure the straight length of a track to be 2.5 mm and you know that the real
ground distance is 100 meters, what is the scale of the photo
21. Focal Length
Focal length is the distance between the camera lens and the film .
The focal length of the lens affects the scale of the image captured.
A camera with a lens of long focal length will produce images which look as if they have been taken
close to the ground.
Conversely a short focal length lens will produce smaller scale photographs which can look as if they
have been taken at altitude.
The scale of a photograph (S) can also be expressed as the ratio between the focal length of the
camera (f) and the altitude of the platform aircraft (H) in the equation
Scale = f/H-h
22. Focal Length
• Example: A camera with a 152 mm focal length takes an aerial photograph from a flying height of 2780m
above sea level and the average elevation of the terrain above sea level is 500m. What is the scale of the
photograph?
24. TYPES OF OVERLAPPING
There are types of Overlapping
End Lap/Forward Overlapping
Side Lap/Lateral Overlapping
25. End Lap/Forward Overlapping
End lap/Forward lap is the overlapping of successive
photos along flight line.
For stereoscopic viewing (60 + 5) end lap is
necessary.
26. End Lap/Forward Overlapping
In hilly areas, 70-80% necessary because of coverage
gap produced by tilt, crab, flying height and terrain
variation etc.
27. Side lap/Lateral lapping
Side lap/Lateral lap is the overlap between photographs
in adjacent parallel flight strip.
For stereoscopic viewing, (30 + 5)% side lap is
required.
28. conclusion
By working on this report we have learnt about the photogrammetry technique
which is used for surveying to prepare the such map like details about the bed of
earth surface, bed rock, types of soil and rocks, the topographic map which give us
information about elevation of various places like hills, valley and river etc. the most
advantages of photogrammetry we prepare the map which shows us the information
about anything which are present on the surface of earth like the position of roads,
rivers, dams, and building etc.
