Calculating the useable field of view for photogrammetry has several elements and here are some rough guides to estimate coverage.
A very useful site for calculating the FOV is here. (Use Dimensional Field of View calculator)
http://www.tawbaware.com/maxlyons/calc.htm
This works well for the total FOV calculations with different lenses at a distance (heights) and also compensates for crop camera sensors. From this we need to then calculate the effective area covered when compensating for overlap.
Photogrammetry requires overlap to correlate the different photos. A typical overlap is 60% in the direction of travel and at least 30% to each side (sidelap). Because the sensor isn't square and the direction of travel overlap is greater, the camera should be rotated to a portrait orientation in relation to the direction of travel.
Example Effective Coverage Numbers
60 ft. 16mm, 1.5 crop factor 60% overlap 30% sidelap
| HZ | 90' | w/ovrlp | 36' |
|---|---|---|---|
| VZ | 60' | w/ovrlp | 42' |
Effective area: 1,512 sq. ft.
80 ft. 16mm, 1.5 crop factor 60% overlap 30% sidelap
| HZ | 120' | w/ovrlp | 48' |
|---|---|---|---|
| VZ | 80' | w/ovrlp | 56' |
Effective area: 2,688 sq. ft.
100 ft. 16mm, 1.5 crop factor 60% overlap 30% sidelap
| HZ | 150' | w/ovrlp | 60' |
|---|---|---|---|
| VZ | 100' | w/ovrlp | 70' |
Effective area: 4,200 sq. ft.
Typically the quality of the aerial photographs is rated in pixels per cm. The obvious tradeoffs are coverage per image vs. quality.
150 ft. 16mm, 1.5 crop factor 60% overlap 30% sidelap
| HZ | 225' | w/ovrlp | 90' |
|---|---|---|---|
| VZ | 150' | w/ovrlp | 105' |
Effective area: 9,450 sq. ft.
Calculating pixels per inch
Square inches/Square pixels = inches per pixel
Ex: Nikon D600 (24mp 6016 x 4016) = 24,160,256 pixels
50.40 m x 33.6 m = 169,344 sq cm.
169,344 / 24,160,256 = .007009 m or 7 mm
Nex5 = 4912×3264 resolution or 16,032,768 megapixels
At 150 ft in height
Convert to square centimeters FOV = 31,354,776 sq cm.
31,354,776 / 16,032,768 = 1.955 cm per pixel
