Aerial Photo Scale Calculator
A free, browser-based calculator. Runs entirely in your browser — no sign up, nothing stored.
Enter Values
How to use this calculator
- Enter the camera's focal length f in millimetres (from the photo's calibration data).
- Enter the flying height above the ground H in metres.
- Optionally enter a distance measured on the photo to convert it to a ground distance.
How it works
For a truly vertical photograph the scale is the focal length over the flying height above the ground: scale = f ÷ H. Expressed as a representative fraction it's 1 : (H ÷ f) with both in the same units.
Any distance measured on the photo multiplied by the scale denominator gives the ground distance. Terrain relief changes the exact scale from point to point, so this is the average (datum) scale.
Worked example
f = 152 mm, H = 1520 m. Scale denominator = 1520 m ÷ 0.152 m = 10,000, so the photo is 1:10,000. A 50 mm line on the photo is 50 × 10,000 ÷ 1000 = 500 m on the ground.
Frequently asked questions
Is flying height the same as elevation?
No — use the height of the aircraft above the ground being photographed, not its altitude above sea level. On varied terrain the scale changes with ground height.
Why isn't the scale exact everywhere on the photo?
A central-perspective photo only has one true scale at the datum; higher ground is closer to the camera (larger scale) and lower ground is smaller. Orthophotos correct for this.
Is this official course material?
No. It is free study support mapped to surveying course levels — not official North Metropolitan TAFE content or advice. Always follow your lecturer and the official assessment brief, and check your own working.
Related tools
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.