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Thanks Hanno,

Whow! Looks too difficult even for me! I think Bygrave/Fuller/ BN much easier for amateur builders and probably get better results. However, a good engineer should be able to do this. ? There is a challenge Hanno. If I build the definitive Bygrave (already done) and BN (soon , I hope), maybe an engineer (like you ?) should be able to build this? Looks good but very difficult. The BN is always going to be easier to build  and probably more accurate than this. It is not exactly a direct plot, but very close and straight onto a flat surface as apposed to a spherical curve. Job done. I guess the constant altitude curves and dec curves use the maths, but the end result is a simple analogue, flat surface system that gives you the answer quickly and easily. Just as easy as a direct plot of circle of equal altitudes I think? Also, you get everything with just 2 quadrants. Still waiting to hear from you maths guys whether we could do an "orange globe direct plot" using just a quadrant or 2? (ie not whole globe) Cant as yet get my brain around that one.

Have a good trip.Nz will probably give you much hope for the future. Generally does.

Francis