Hi Dragan

Many thanks for your reply.

Another question or two if I may!

1) How do you know the total angle of your camera? Is this sort of thing in the manual?
2) When the obstacle is a square (or I suppose a sphere) do I need to concern myself with the total vertical angle? (i.e. is the total horizontal angle not sufficient?)

For example:-

       nMaxPx=1280
       nPx=17
       nWidth=1.25
       nMaxAngle=88
 
       nAngle=nMaxAngle/180*pi()*nPx/nMaxPx
       nDistance=nWidth/atan(nAngle)

3) Are you aware of a link that gives more details of this algorithm?
4) Would you be able to parenthesise the expressions above to establish correct operator precedence?

Thanks again