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4. Examples
Example 1
Two vertical control points appear on adjacent aerial photographs. Photography flying height is unknown although it is needed for later computations. The elevation and and x coordinate on each photo for the points are:
Point | Elev (ft) | x (mm) | x' (mm) |
T34 | 882.53 | 60.922 | -35.909 |
M60 | 849.93 | 29.538 | -66.379 |
Determine the flying height.
Solution
Compute parallax for both points
Re-arrange Equation E-8 to solve flying height
H = 4.30x10^{3} ft
Example 2
A telecommunication tower appears on overlapping photographs. Coordinates of its top and bottom are:
Left | Right | |||
Point | x, mm | y, mm | x, mm | y, mm |
Bottom | 23.84 | -15.61 | -12.41 | -15.62 |
Top | 29.75 | -47.85 | -18.23 | 47.89 |
The terrain is generally flat and elevation at the tower base 1125 ft. The flying height was 3550 ft and camera focal length 152.44 mm. What is the tower height?
Solution
Compute parallax for tower top and bottom
Use Equation E-7 but don't add the tower's base elevation.
Elev = 590 ft