SRV-29

Photogrammetric flying height

H = f B / p. Air base B, focal length f, parallax p of a point.

Reading speed

PhotogrammetryParallax height

Governing equation

H=f B/p

where

f: Focal length (mm)
B: Air base (m)
p: Parallax (mm)
H: Flying height (m)

Lecture brief

Historical brief

From chain and theodolite through Bowditch’s compass-rule (1802) to GPS PDOP, surveying is the propagation of small errors across a network. These sheets close traverses, reduce stadia and state map scale. This sheet (SRV-29 — Photogrammetric flying height) is the form associated with Parallax height. Working symbols: $f$ , $B$ , $p$ $\rightarrow$ $H$ . Similar triangles in a stereo pair. Differential parallax dp gives Δh = (H² / (f B)) dp ≈ (H/p) dp.

Purpose

Purpose: compute

H

from

f

B

p

in Surveying via

H=f B/p

H = f B / p. Air base B, focal length f, parallax p of a point. Use it when a real surveying question must be answered in SI before a code check.

Live realistic example

In symbols

Live case. Given

f = 152.000\,\mathrm{mm}

B = 450.000\,\mathrm{m}

p = 12.000\,\mathrm{mm}

, the governing relation

H=f B/p

yields

H = 5700.0\,\mathrm{m}

. Two photos, a floating mark, a height. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

Focal length f152 mmAir base B450 mParallax p12 mm

Outputs

Flying height H5700.0 m

Reading speed

Watch on YouTube

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Narration of this film

Two photos, a floating mark, a height.

Similar triangles in a stereo pair. Differential parallax dp gives Δh = (H² / (f B)) dp ≈ (H/p) dp.

Reading speed

Watch on YouTube