NavList:

Thanks, Frank!

Your article is very relevant to what I was trying to ask.

I meant to clarify (for myself in the first place) that advancing a LoP by drawing a parallel line at a certain gap is NOT the same thing as an evaluation of the altitude of the first body at the time (and place) of the second sight. To do this evaluation the very different set of calculations is required. Period.

I started this topic because I am/was tempted to use "Lop advance gap" (call it " dH₁") as an altitude correction to use the (H₁+ dH₁) as the "altitude proper" along with the H₂ for direct calculation of the CoP's (circle of position) intersections. Several my attempts at this failed, so I started thinking why it fails?

Also, this my disillusion has re-surfaced when I read the "no plotting sheet required" booklet, where the LoP advance "gap" was given the Δh_z name. I wanted to get rid of this delusion once for all.

Thank you very much, your article helped me with this issue.

I hope Mike also could learn something useful from this particular thread, may be my "explanation" of the LoP advance procedure as the correction for the movement of the observer was not too unclear.

Warm regards,
Tony
60°N 30°E