Measuring distance with a photograph...

[Wildewinds]

I believe this is a math question more than anything else...

Let's say a specific object it 60" long. If I take a photograph of the object from an unkown distance using a 200mm lens, is there a way to measure how far away it is by measuring how big the object is at that distance?

Let's assume I'll first take a picture of it from a known distance first so I can use that photo to compare it with the distance photo.

I assume accuracy would decrease the farther away the object is, but can I expect any real degree of accuracy at about 1500 feet with a 60" object?

Any help would be appreciated.

[KatmanDu]

I think it's called photogrammetry (sp?). Accident reconstructionists will use it when they only have photos of the wreck scene to work with, either because no measurements were taken or the baseline markings are gone for some reason. There are also a lot of other applications, obviously. Try http://www.univie.ac.at/Luftbildarchiv/wgv/intro.htm
for a basic intro...

I think that's what you were asking about...