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Chapter onePhotogrammetry and Photo
Interpretation

• LaAd2052

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Cont.

• What is Photogrammetry?
• The science, art and technology of obtaining
  reliable measurements through the process of
  recording, measuring and interpreting
  photographic images.
• Photogrammetry can be defined as the art,
  science, and technology of obtaining reliable
  information about physical objects and the
  environment Science of measuring in photo
  qualitatively and quantatively
• Photogrammetry is the first remote sensing
  technology ever developed.

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• Photogrammetry is an art, because obtaining
  reliable measurements requires certain skills,
  techniques and judgments to be made by an
  individual.
• It is a science and a technology because it takes
  an image and transforms it.
• The photogrammetric process consists of project
  planning, image acquisition, image processing,
  and control data for image orientation, data
  compilation and presentation of an end product.
• The end product of the photogrammetric process
  can be coordinate values of individual points, a
  graphic representation of the ground surface
  (topographic map), or a rectified image of the
  ground surface with map-like characteristics
  (orthophoto.)

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• Images used for photogrammetry can originate
  camera, an ordinary camera or from digital
  sensors.
• The image can be recorded from a device mounted
  on a satellite, on an airplane (including
  helicopters), or on a tripod (terrestrial
  photogrammetry) which is set up on the ground.
• In this module, only applications that are based
  on aerial photographs recorded with a metric
  camera will be discussed.

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Photographs

• Its most important feature is the fact, that the
  objects are measured without being touched.

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PHOTOGRAMMETRY

• objects are measured WITHOUT TOUCHING.
• It is a REMOTESENSING technique.
• It is a close range method of measuring objects.
• It is a 3-dimensional coordinate measuring
  technique that uses PHOTORAPHS as the fundamental
  medium for measurement.

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CLASSIFICATION 1 from analysis perspective

• Metric Photogrammetry making precise
  measurements from photos and other information
  sources to determine, in general, the relative
  locations of points.
• This enables finding distances, angles, areas,
  volumes, elevations, and the sizes and shapes of
  objects.
• The most common application of metric
  photogrammetry is the preparation of planimetric
  and topographic maps from photographs.
• Interpretative Photogrammetry recognizing and
  identifying objects and judging their
  significance through careful and systematic
  analysis
• depending on our own individual perceptions and
  experience

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Modern photogrammetry covers a considerably wider
domain. Imagery of all types, both passive, such
photography, and active such as radar imaging, is
used. The imagery may be collected either in
hardcopy form (e.g., on film) or in digital
form by electro-optical sensors. The analysis may
be performed on single images or on overlapping
(stereo) imagery The fundamental task of
photogrammetry is to rigorously establish the
geometric relationship between the image and the
object as it existed at the time of the imaging
event.
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Once this relationship is correctly recovered,
one can then derive information about the object
strictly from its imagery This relationship can
be established by various means, which can be
broadly classified into two categories analogue,
using optical, mechanical, and electronic
components or analytical
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CLASSIFICATION 2 location perspective

• Terrestrial Photographs
• Aerial Photographs

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TERRESTRIAL PHOTOGRAPHS
Taken from the ground Normal cameras can be
used
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TERRESTRIAL PHOTOGRAPHS
Photo Thodolite is used to acquire precise
terrestrial photos
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TERRESTRIAL PHOTOGRAPHS
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AERIAL PHOTOGRAPHS
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AERIAL PHOTGRAPH VS. PLAN/MAP
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Components of photogrammetry
 In general, photogrammetry has three major
components. These components are image
acquisition, image control and product
compilation.   Image acquisition - includes
planning the over flight, selecting an
appropriate camera system, photo taking film
processing, film inspection and annotation,
printing of paper prints and diapositives, and
image scanning (if necessary.)   The control
component - includes selecting locations for
ground control and targeting, field surveying
control points and aerial triangulation., this
component could be eliminated when advanced GPS
methodology will be able to solve the photo
orientation problem without needing ground
control.
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Components of photogrammetry
  The product compilation component - of
photogrammetry varies and depends on the nature
of the product. Topographic maps, orthophotos, or
monoscopic updates are all photogrammetric
products. A successful photogrammetric survey
project depends on a thorough understanding of
these components
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Role of Photogrammetry in a GIS
 In fact, Heipke 2004 has identified the role
of imagery within a GIS as Imagery is the prime
means of geospatial data acquisition. Imagery is
the ideal medium to use as a base or backdrop
upon which map data can be overlaid to facilitate
the user understands of the GIS data. As 3-D
rendering increases, imagery is critical in
providing a more realistic rendition of the
conditions found at this site.  A third issue
relates to the handling of change within an area
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Advantages of photogrammetry
 Some advantages of photogrammetry over
conventional surveying and mapping methods
are It provides a permanent photographic record
which have metric characters 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. It can provide a large mapped area can
be used in locations that are difficult, unsafe,
or impossible to access///it is an ideal
surveying method An extremely important for road
surveys can be done without closing lanes Once a
road is photographed, measurement of road
features, including elevation data, is done in
the office, not in the field.  Inter visibility
between points and unnecessary surveys to extend
control to a remote area of a project are not
required
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Limitations of photogrammetry
 Every science is not perfect. Therefore,
photogrammetry has also its own
limitations Weather conditions (winds, clouds,
haze etc.) affect the aerial photography process
and the quality of the images. Hidden grounds
caused by man-made objects, such as an overpass
and a roof, cannot be mapped with
photogrammetry. The accuracy of the mapping
contours and cross sections depends on flight
height and the accuracy of the field survey
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END OF LECTURE 1