[Kstars-devel] HTM questions

[Jan Kotek]

Hi,
I have a few questions about HTM indexing mechanism. My program is
using Java version. I know howto convert point to it trixel
representation.  My program is using it and it works as charm.

But after a few days of trying I still do not know how:

1) convert area (ellipse, pollygon) to set of trixels
2) get neighbours of trixel in defined distance (ie get all objects in
distance from point)
3) convert trixel to ra dec coordinates (ie inverse function).

Did you handle this in KStars? Can you point me to source code?

Thanks Jan Kotek
http://kotek.net/opencoeli

PS:
There is also an alternative to HTM:
HEALPix (Hierarchical Equal Area isoLatitude Pixelization).
http://healpix.jpl.nasa.gov/index.shtml

Features are impressive..  It is more simplier then HTM (does not uses
trigonometry), well documented and should be very portable.