Topic: Calibration an angle correction

Hello,

I measured some angles of a quadruped and I would like to correct the perspective effect for these angle measurements.

http://zupimages.net/up/16/38/uqr9.png

1) How can I do to retrieve the perspective grid properties ?

2) After having retrieved grid perspective properties, which mathematical function can I apply to my angle measurement so as to obtain corrected angle measurements ?

In fact, I have already my angle measurements and I would like to correct them.

Thank a lot for your help