Photo Mosaic and Orthophoto

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Photo Mosaic and Orthophoto
Dr. M. M. Yagoub Department of
GeographyFaculty of Humanities and Social
SciencesUnited Arab Emirates UniversityP. O.
Box 17771, Al-Ain United Arab Emirates Tel
00971-3-7064-674 (O)Tel
00971-3-7612-316 (H)Fax
00971-3-7671-706 E-mail myagoub_at_uaeu.ac.ae E-
mail myagoub_at_hotmail.com URL
http//www.angelfire.com/mo/yagoub
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Mosaic (page 93)

• An aerial mosaic is an assemblage of two or more
  individual over lapping photographs to form a
  single continuous picture of an area . The
  assembly is made by cutting and piecing to gather
  part s of photographs , being careful to make
  common images coincide as closely as possible at
  the match lines between adjacent photos .

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Photographic coverage
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FIRST MOSAIC
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Mosaic advantages

• Show relative planimetric qualities , whereas
  objects on maps which are shown with symbols must
  be limited in number .
• Mosaic of large areas can be prepared in much
  less time and at considerably lower cost than
  maps
• it is easy to understand and interpreted by
  people without photogrammetry or engineering back
  ground .

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Uses of mosaic

• Mosaic are widely used . Their value is perhaps
  most appreciated in the field of planning , both
  in land-use planning and in planning for
  engineering project .
• Use to study geologic features

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Orthophoto (page 90-91)

• Aerial photographs are not planimetric map,
  because they have geometric errors ,those error
  comes from tilt and relief displacement .and when
  we correct the photos from those problems the
  result is Orthophoto .

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Orthophoto Maps

• It show the correct planimetric position and
  preserve consistent scale throughout the image it
  valuable because they show the fine detail of an
  compiled much more quickly and cheaply than the
  usual topographic maps .

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Mosaic-photomap

• A photo is central projection while map is
  orthographic projection
• Tilt and distortion in a photo can be eliminated
  using restitution instruments
• A photo that is free from tilt and distortion
  (relief displacement) is called orthophoto
  (Planimetrically correct aerial
  photograph-orthophotoscope)
• A series of adjacent photos can be overlapped to
  produce a mosaic
• In the past orthophoto is produced by optical
  means, currently it is produced by using computer
  algorithm and image processing software
• Names and other information can be added to the
  mosaic to produce photomap-orthophotmap

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