Difference Between Orthophoto and Aerial Photo Quiz

Study Notes

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

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

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 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

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