What tool(s) to use to make measurements in photogaphs for 3D design?

[Raymond Herrera]

Note: This is the first forum that I could think of for this question. If you know of one, please point me to more specialized sites.

I do a lot of 3D modeling based on photos and need to know the object's dimensions as accurately as possible. Sometimes people in my job are lucky to find "straight" (forgot the actual name) images. This is an excellent example:

Alas, I need something more general.

TIA

-Ramon F Herrera
JFK Numbers