# Recreate aerial photograph: find correct position

My father has an old aerial photograph of the neighbourhood where he lives (and where I grew up), while it was still under construction, taken around 1975. It's not digital of course, but I photographed it (higher resolution in this Dropbox folder):

Over 40 years later, some things have changed and some things have stayed the same: (Aerial view from Google Maps)

My cousin has a drone, and we're planning to recreate that photograph to better compare things now and then. I'd like to get as close as possible to the original perspective, meaning we should try to position the drone as close as possible to where the camera was originally. I tried it out in Google Earth and Google Maps, and it turned out to be harder than I expected.

Are there any tricks to do this, or is mainly trial-and-error?

1. draw VERTICAL lines through selected landmarks in your photo

1. draw lines through the same landmarks on the map and find the crossing point

1. repeat using more lines and more landmarks for better precision

2. this simple method does not give you any information on the altitude - just fly up until your picture starts to look right :)

To get the same perspective you'll need to not only shoot from the same optical axis, but also from the same distance above the ground.

To do it either mathematically or via trial and error you'll need to select three points that are constant in both photos and triangulate the camera position in the original photo from them. The very complex math/geometry involved in such triangulation is probably better reserved for one of the mathematics sites here at stack exchange.

I have a strong hunch that at the altitude of the original photo your drone will be too far from the ground to recreate the same field of view (unless your drone's camera has a much longer than a typical drone's focal length), so you'll probably wind up having to crop the drone image to match the field of view.

• Yes, I know, most likely the we'll have to crop. Or compromise and get a bit closer, even if it means we lose the perfect perspective. – Roel Schroeven Dec 26 '17 at 19:13