Re: [Opengc-devel] nav display status

[Manuel B. <li...@va...>]

On Fri, May 09, 2003 at 08:15:23PM -0400, Damion Shelton wrote:
> Thanks for the reply,
> 
> I've been doing some reading today (I find this an interesting problem) 
> and came up with the following information:
> 
> According to http://mathworld.wolfram.com/topics/MapProjections.html 
> the Lambert conformal conic projection does not display either great 
> circles (orthodromes) or lines of constant heading (loxodromes) as 
> straight lines. Apparently, one of the few projections where 
> orthodromes are straight lines is the gnomonic projection, but it's 
> nonconformal (does not preserve small angular relationships) and 
> results in rather extreme distortion away from the center of the 
> projection.

Hmmm... I thought that lambert did show great circles as straight
lines... but its been several weeks since I looked into this.
I do remember looking at gnomonic projections, maybe I was confusing
those... I just have forgotten what I came up with thru my research.
I must have taken some notes... just have to find'em in my filesystem.

What I seem to remember is that the best projection was the one most
frequently used for aviation maps.

Once I get to the ND part of my glass cockpit software, I'll have to
come back looking at the projections.

BTW: for conversion routines, there's the PROJ project. This might help
you in OpenGC

Some time back I looked at OpenGC and what kind of
transformation/projection you used... this seemed to be a special local
projection from the Netherlands, if I remember correctly. I was
wondering why you choose that one.



My project (X11GC) can be found at:
http://cockpit.varxec.de/software/x11gc.html
along with my flightgear-based cockpit contruction project:
http://cockpit.varxec.de


Regards,
Manuel