photogrammetry cont.. stereoscopic parallax f the apparent displacement of the position of an object...
Post on 23-Dec-2015
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Stereoscopic Parallax The apparent displacement of the position of an object wrt a
frame of reference due to a shift in the point of observation, try it.
The shift is along the line of movement. The closer the object to the frame, the larger the shift for the
same shift, so parallax is a function of height. Parallax equations:
H-h = BfP
Parallax = p = x - x1
What is (x) ?get the flying heightor point elevation
X = Bp x Y = B
py
get ground coordinates
Stereoscopic Viewing The theory of
stereoscopic viewing and parallactic angles
Conditions for viewing a stereo model
Stereoscopic Plotters To compile maps, take cross sections, and DEM Three main components:
– Projection system– Viewing system– Tracing system
Major Types: – Optical, mechanical.– Analytical, and softcopy systems: mathematical model, require
computers
Orthophotos
Orthographic projection of photographs. Uniform scale, no relief displacement. Serve as maps Produced by “rectifying “ the photographs,
now mainly through “digital image processing”.
Advantage of orthophotomaps
Ground Control for Photogrammetry Each model requires three horizontal and four
vertical control points. Control points are chosen before (marked) or
after (usually) and measured by ground surveying
Using “Aerial Triangulation” control can be intensified on the photos
GPS may eliminate the need for ground control.
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