Getting precise geometry with an image


Hello! I am new here and would have an important question that I can’t seem to answer myself.

I am basically taking an easter egg shell, super glueing it closed, drilling a hole in it, inserting a tube, and making it waterproof. I am then going to place a light source in the center and place fluence detectors along the boundary of the cavity.

It is incredibly important that I know the precise geometry of the cavity so that I can calculate the distance from the central tube to the outer shell and calculate other pertinent values.

I was thinking that I could take a photo of the egg and measure the dimensions through that – but many problems are introduced like parallax, etc. Theoretically I should be able to do this. PLEASE HELP!

Maybe Imagej Is not the answer, but I am confident that I can use this program to create a geometrical map.