[Proj] Troubles with Newton-Raphson inverse projections
support.mn at elisanet.fi
support.mn at elisanet.fi
Sun Oct 19 01:25:43 EDT 2008
"Gerald I. Evenden" <geraldi.evenden at gmail.com> kirjoitti:
>
> Secondly, finding the root may also be difficult when the precision of the
> derivatives start to fail. This is the case near the poles of both the
> Hammer and Aitoff projections. At a latitude greater than 89° the method
> fails for both these projections. One also gets suspicious that this will
> occur when the nature of the curve flattens out like the top of a sine curve.
> I have not tried the flat pole Winkel Triplel yet.
>
Can't you just switch the method near poles? Something like:
if (lat > 88) use_special_derivatives();
else use_normal_derivatives();
And figure out from the formulas (code) what is causing the problem near poles
and then eliminate that by using something that is more efficient near poles.
Regards: Janne.
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