Re: [Flightgear-devel] Global data positional lookup

[Christian M. <ma...@Ch...>]

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Mathias Fr=F6hlich schrieb:
> On Sunday 19 February 2006 19:44, Christian Mayer wrote:
>> As my last post to this topic was probably a bit cryptic for some I've
>> looked in the net a bit and have found:
> Hehe, not really cryptic.
> Rather interresting!

For people who can read German,
http://www5.in.tum.de/lehre/vorlesungen/algowiss/ss05/vorlesung/rfk.pdf
has a great and easy understandable introduction to this topic.

>=20
>>   http://taltos.pha.jhu.edu/htm/
>>
>> Probably we can use their software directly - or use their algorithm t=
o
>> partition the earth in such a way that we can cheaply query points (li=
ke
>> navaids, METAR stations, ...) on the earth.
> Ok, a 'triangular quadtree' :)
> Should not be too hard to implement.

I think so, too. And it would be handy in quite a few places in FG.

<puting on flameproof suite>We could even change the scenery format to
use this as a base</puting on flameproof suite>

> Your note was that well done that it appeared that you will come up wit=
h an=20
> apprioriate solution in a few minutes ...

In a few minutes I had written a program that converts a 3D ball with
the peano curve into 1D - and then turns it into 2D to plot it.
It looked quite interesting and very abstract :)

> At least it made me believe that you already have something more or les=
s ready=20
> to share ...

No, not in C++ code.
(Again for people who understand German and have Maple,
http://www5.in.tum.de/lehre/vorlesungen/algowiss/ss05/material.html
has a few Maple-Worksheets that show some useful properties of the space
filling curves)

The Code / Ideas I had so far was mainly working on a unit square or a
unit cube. But I soon came to the conclusion that that wasn't optimal
for mapping spherical coordinates as it doesn't care about the "seams".
So thinking and searching for a better solution I came up with the link
above. This could help us answer all the locality questions very fast
with only very few code.

CU,
Christian


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