Photogrammetry-part 1

Topics
Photogrammetry, Part-1
• Aerial photography – Types of aerial
cameras,
• Types of photographs, vertical, horizontal,
oblique.
Prasenjit Bhowmick

WHAT IS PHOTOGRAMMETRY?
FROM GREEK ROOT WORDS:
 - Y THE SCIENCE OF
 - GRAM SOMETHING WRITTEN OR DRAWN
 - METR MEASUREMENT
 - PHOTO WRITING WITH LIGHT (PHOTOGRAPH)
THE SCIENCE OF MAKING MEASUREMENTS FROM
PHOTOGRAPHS.
THE MOST COMMON APPLICATION OF PHOTOGRAMMETRY
IS MAKING MAPS.
Photogrammetry
Elements of Photogrammetry

What is Photogrammetry ?
Measure objects (2D or 3D) from Aerial photographs
and stereo images.
without being physically touched.
The results can be:
• Coordinates of the required object-points
• Topographical and Thematic maps
• DEM
• Orthophoto (Rectified photographs)
Photogrammetry

History of Aerial Photogrammetry (Photography)
• 1858, French Photographer, G.F.Tournachon took the
first Aerial Photograph of Paris City from a balloon.
• In 1895, Laussedat, created the first suitable camera
and procedure, called metro photographic
• In 1908 first Aerial Photograph was taken from
Airplane over le mans, France by Wilbur Wright
Photogrammetry

• World War I (1914) Lt. Law used Airplane
to take photographs of Germany.
• World War II (1939-45) all the countries
involved in the war made extensive use of Aerial
photography
• By the year 1940, Aerial photography as applicable
to study of geology, forestry etc.
Photogrammetry

History of Aerial Photogrammetry (Instruments)
• Until ~1980, opto-mechanical devices were used for
Photogrammety (Hardcopy photogrammetry)))
• Hardcopy photogrammetric instruments include:
– Monocomparator
– Stereocomparator
– Rectifier
– Streoscope
– Stereoplotter
Photogrammetry

• The advent of the desktop computer has brought about the
transition to fully digital systems (softcopy photogrammetry)
Typical components of a softcopy photogrammetric workstation:
Photogrammetry
Computer
Storage Scanner
Keyboard
and mouse
3D cursor
Stereo monitor
Monitor
Hardcopy
output
Network

AERIAL CAMERA
 Aerial Camera is one of the most important instrument in the
photgrammetry
 It is used to obtain the photographs upon which
Photogrammetry depends
 Success of Photogrammetry in recent years is due to availability
of high precision cameras
 The requirements of aerial mapping cameras are quite different
from those of ordinary amateur cameras
 The most common frame or format size of aerial cameras is 9 in
(23 cm) square
Photogrammetry

AERIAL CAMERA
 The primary requirement of any
photogrammetric aerial camera is a lens of
high geometric quality.
 Aerial cameras must be capable of exposing
great number of photographs in rapid
succession.
 Must have short cycling times, good lenses
and efficient shutters.
 They must be capable of functioning under the
most extreme weather conditions and in spite
of aircraft vibrations.
Photogrammetry

AERIAL CAMERA - Development
 The most important development is the perfection of lenses
of extremely high resolving power and almost negligible
distortion
 This has greatly increased the accuracy of photogrammetry
 Photographs in digital form. Earlier Aerial cameras use roll
film and have magazine capacities of from 200 to 400 ft or
more
Photogrammetry

TYPES OF AERIAL CAMERAS
Four main types of aerial cameras are
(1) Single-lens frame cameras,
(2) Multi-lens frame cameras,
(3) Strip cameras,
(4) Panoramic cameras.
Photogrammetry

1. Single-lens frame cameras,
 Single-lens frame cameras are the most common cameras in
use today.
 Used exclusively in obtaining photographs for mapping purposes
because they provide the highest geometric picture quality.
 The lens is fixed relative to the focal plane.
 The film is generally fixed in position during exposure,
Photogrammetry

 Single-lens frame cameras are often classified according to their
angular field of view.
 Angular field of view is the angle subtended at the rear nodal point of
the camera lens by the diagonal (d) of the picture format.
Photogrammetry
(a) Normal angle (up to 75°)
(b) Wide angle (75 to 100°)
(c) Super-wide angle (greater than 100°)
'- Rear nodal point of camera lens

Photogrammetry
 Available in a variety of focal lengths.
 mapping photography has a 6-in (152-mm) focal length and 9-
in-(23-cm) square format,
 Other format include
 3.5 in (89-mm),
 8.25 in (2IO-mm) and
 l2-in (305-mm) focal lengths
 The 6-in focal length with 9-in format provides the best for
geometric mapping.
 Longer focal lengths of 12 in are used for aerial mosaics and
for reconnaissance and interpretation purposes.

Photogrammetry
Fairchild KC-6A aerial mapping camera Wild RC-IO aerial mapping camera
The RC-1O is having nominal focal
lengths of 3.5 in (89 mm), 6 in (152
mm), 8.25 in (210 mm), or 12 in (305
mm).
Nominal 6-in- (152-mm)focal-
length lenses

Photogrammetry
 12-in (305-mm) focal length.
 film capacity is 4,000 ft (1,220 m).
 principal is addition to topographic mapping,
lTEK LFC Large Format single-lens frame camera
Hasselblad MK-70 camera
 The Hasselblad camera is a small format
single-lens frame camera
 used extensively for space photography.
 uses 70 mm film and can be obtained with
various focal-length lenses

2. Multi-lens Frame Cameras
 Have two or more lenses and expose two or more pictures
simultaneously
 All lenses simultaneously expose the same area,
 Different lenses contain films
 Also referred to as multi-spectral cameras..
Photogrammetry
MPC multilens camera - having six lenses

3. Strip Cameras
 Strip cameras takes continuous photograph of a strip of terrain
 The film passes over a narrow slit opening in the focal plane.
 Strip cameras may use a single lens or they may have two
lenses to get stereoscopic coverage.
 Useful in Route studies for Highways, railroads, pipeline etc.
Photogrammetry

Photogrammetry
4. Panoramic Cameras
 Panoramic cameras photograph a strip of terrain from horizon to
horizon.
 The strip terrain taken transverse to the direction of flight
 The exposure is made by specially designed camera which scans
laterally from one side of the flight path to the other
 The lateral scan angle angle may be 1800, in which case the
photograph contains a panorama of the terrain from horizon to horizon.
 Panoramic camera are generally of two types.
1. Scan by rotating the lens
2. Scan by rotating prism in front of camera lens

Photogrammetry
Panoramic Cameras

Types of Photographs
Two basic classifications of photographs used in
photogrammetry are
1.Terrestrial
•Taken from ground based cameras
2. Aerial
•Taken from air based cameras
Photogrammetry

Types of Aerial Photographs
Aerial Photographs can be classified in the following
manner
1. According to orientation of camera axis
2. According to Lens system
3. According Film properties
Photogrammetry

1. According to orientation of camera axis
 The vertical
 The oblique
• depends upon the angle of the camera
• with respect to the earth's surface
Photogrammetry

Vertical Photographs
Camera points as straight down as possible
Allowable tolerance is usually ± 3° from the plumb line
Plumb line coincident with the camera axis
A vertical photograph has the following characteristics
The lens axis is perpendicular to the surface of the
earth
It covers a relatively small area
The shape of the photos closely a square or rectangle
Distance and directions of maps if taken over flat
terrain
Relief is not readily apparent
Photogrammetry

Relationship of the vertical aerial photograph with the ground
Photogrammetry

V
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Photogrammetry

Low Oblique Photographs
Camera inclined about 30° from the vertical
- Characteristics -
Covers a relatively large area
Ground area covered is a trapezoid, although the
photo is square or rectangular
It have more familiar than viewing from the top
of a high hill or tall building
No distance can measure with Scale.
Azimuth cannot be measured
Relief is perceptible but distorted
It does not show the horizon
Photogrammetry

Relationship of low oblique photograph to the ground
Photogrammetry

L
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Photogrammetry

High Oblique Photographs
Taken with the camera inclined about 60° from the
vertical
Limited military application
- Characteristics -
Covers a very large area (not all usable)
Ground area covered is a trapezoid, but the photograph
is square or rectangular
Distances and directions are not measured
Relief may be quite discernible but distorted as in any
oblique view.
The horizon is always visible.
Photogrammetry

High oblique photograph
Photogrammetry

Vertical aerial photograph.
Low-oblique aerial photograph.
High-oblique aerial photograph
Pc: Kahola, Kansas.
Photogrammetry

Photogrammetry-part 1

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Photogrammetry-part 1