# Trigonometry and calculating the elevation angle from aerial photography

I was wondering whether anybody could advise me on a way to calculate the elevation angle from a camera to an object in an aerial photograph taken from a known elevation with no suitable reference objects.

Ultimately I would like to measure particular features within an image. I was thinking of a solution using trigonometry. Attached is a diagram illustrating the problem, as well as a sample of a picture to apply this to.

In the diagram, A represents the position of the camera. The Red triangle represents the focal view of the images. B is the centerpoint of the images. The Blue rectangles are objects I would like to measure.

To do it this way, I need to solve either angle E or F, however given that there is not tilt/angle/axis data stored within the photos EXIF metadata, I think the only way to do this would be to project the ground plane onto the image which I believe will allow me to calculate angle F. However I am unsure or unaware of whether there is software which may make this feasible?? As the goal would be for the solution to be applied to a series of photographs where the elevation angle could vary widely.

There aren't parallel lines, shadows, or objects of known size. However, topography shouldn't be an issue as the surface is flat (see image of ice).

• What camera is used to take photos? In most cases, there is some distortion in photos that can be eliminated by some not very easy technique. Hardly this is a matter of trigonometry. – Vadym Feb 8 at 15:09
• Photos are over 10 years old. Camera was a Canon EOS 40D – JinfengArsene Feb 8 at 15:32
• First of all the distortion of the camera should be eliminated using, for example, Adobe Lightroom software. Then you could calculate the desired angles only with the assumption that this photo was taken with the lens parallel to the surface i.e. the scale is the same in each point of the image. But I suspect that this is not the case according to change in size of the seals from the front to the back. Look at the character. Most of problems discussed in the paper: cis.rit.edu/class/simg782/lectures/lecture_02/lec782_05_02.pdf – Vadym Feb 8 at 16:14
• The images are not taken with a lens parallel to the surface. That's why i suggested the approach using trigonometry – JinfengArsene Feb 8 at 16:52
• Welcome to GIS SE! We're a little different from other sites; this isn't a discussion forum but a Q&A site. Please check out our short tour to learn about our focussed Q&A format. You had a tag for ArcGIS Desktop but make no mention in your question body as to how that relates to your question, and so I have removed it. – PolyGeo Feb 10 at 23:00