Photogrammetry Through Cell phone

[Ayman]

Hello,

I am a newbie in this field and as a beginner I am having problem in finding interior orientation parameters of my cell phone (from which I am taking pics).

Also, I am given a task to find the ground distance between two points by the formula f/H=x/X 

where f=focal length of phone camera

            H=total height

            x= image distance between  points

            X= ground measurements between points

The problem is that how to measure image distance. I mean if my display is small my points will show smaller difference whereas if the display is large my points will appear far. Also any app to calculate this image distance or the traditional ruler will work (accuracy issues). Attached image viewed from Cannon 60d DSLR but the image is shot from cell camera (Samsung Note 5).

Thank you.