Aerial Photo Mosaic and Orthophoto
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Questions and Answers

What is the main advantage of using a mosaic over a plan?

  • It can be produced more quickly and contains more landform detail. (correct)
  • It is more suitable for geological investigations.
  • It provides more accurate measurements.
  • It is easier to understand for people without a background in photogrammetry or engineering.
  • What is the primary characteristic of a controlled mosaic?

  • It has a lower level of accuracy compared to semi-controlled mosaics.
  • It is used primarily for geological investigations.
  • It is constructed from unrectified photographs.
  • It is prepared using ground control points. (correct)
  • What is the minimum end lap required for mosaic work?

  • 60% (correct)
  • 50%
  • 30%
  • 40%
  • What is the purpose of rectification in controlled mosaics?

    <p>To reduce the effects of relief and tilt displacement.</p> Signup and view all the answers

    What is a characteristic of uncontrolled mosaics?

    <p>They are prepared by matching image details of adjacent photos.</p> Signup and view all the answers

    What is the primary reason for creating a mosaic from individual photographs?

    <p>To obtain a more extensive coverage of an area</p> Signup and view all the answers

    What is the key difference between a mosaic and an orthophoto?

    <p>A mosaic is corrected for tilt and relief displacements, while an orthophoto is not</p> Signup and view all the answers

    What is the benefit of using special cameras to photograph large areas from the air?

    <p>It reduces the effect of blind areas</p> Signup and view all the answers

    What is the purpose of using marked and known ground reference points in constructing a mosaic?

    <p>To scale the individual photographs</p> Signup and view all the answers

    What is the end product of constructing an orthophoto?

    <p>A contoured photograph with small errors of position and height</p> Signup and view all the answers

    Study Notes

    Photo Mosaics and Orthophotos

    Types of Mosaics

    • Aerial mosaic: an assemblage of two or more individual overlapping photographs to form a single continuous picture of an area
    • Three types of mosaics:
      • Controlled mosaic: horizontally controlled by picture points established on the ground, constructed to give both high pictorial quality and good accuracy
      • Semi-controlled mosaic: utilizes some combinations of specifications for controlled and uncontrolled mosaics, prepared by using ground control
      • Uncontrolled mosaic: prepared by matching image details of adjacent photos, no ground control, no rectification, easier and quickly prepared than controlled mosaic

    Characteristics and Advantages

    • Mosaics show relative planimetric qualities, whereas objects on maps are shown with symbols and must be limited in number
    • Mosaic of large areas can be prepared in much less time and at a considerably lower cost than maps
    • Easy to understand and interpret by people without photogrammetry or engineering background

    Preparing Photo Maps

    • Overlapping photographs are placed down consecutively and stapled to a board
    • No height control is used during assembling
    • Central portion of a photograph is trimmed away, leaving a small amount of overlap
    • Minimum of 60% end lap and 30% side lap is required for mosaic work

    Rectification of Photographs

    • Rectification process allows for bringing all rectified points to the same scale
    • Rectification produces an equivalent truly vertical photograph, minimizing effects of relief and tilt displacement
    • Graphical and optical-mechanical methods are used for rectification

    Uses of Orthophotos

    • Orthophoto: a corrected photograph that has been corrected for tilt and relief displacements
    • End product may be a contoured photograph to correct scale containing very small errors of position and height
    • Useful in flood control, geological investigations, or irrigation works, where ability to see the areas involved is crucial

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    Description

    Learn about the concepts and applications of aerial photo mosaics and orthophotos, including their types, advantages, and uses in geographical mapping.

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