"Wolfgang Wieser" <wwi### [at] gmxde> wrote in message
news:40118be9@news.povray.org...
>
> I'm rendering landing sites as well currently, but Christoph was
> faster, as always :)
>
> Just a question:
> Spirit is located at 14.59 S, 175.30 E (IAU 2000)
> Is my assumption correct that we're in the tile megt00n090.. ?
> (I just want to be sure, there seem to be different zero longitude
> definitions around...)

Yes, that's the one. "000" for longitudes 000 to 090, "090" for 090 to 180,
"180" for 180 to 270, lastly "270" for 270 to 360. Apparently only files
needed are the megt*.img ones too.

What confused me at first was how the megt00n000hb.img to megt00n270hb.img
tiles are really for the southern hemisphere too. As you might have already
discovered, it goes southward from 00*n* to 44s and for northward is 44n to
88n. Oh, and watch out for those missing 2 degrees at the poles. I finally
worked that out for a orthographic rendering which pieces all the tiles
together for a spherical image map I used afterward. Polar tiles were
shifted up or down by about 6% of a unit, for my unit-sized tiles which are
30 X 30 degrees each.

I'm using 3DEM, http://www.visualizationsoftware.com/3dem/downloads.html ,
to convert those IMG files to bitmaps and it's both free and very good at
manipulating or displaying them.

P.S.
Something strange about the Mars image/bump maps I got from
www.space-graphics.com was that I needed to rotate a little to align with
POV's map_type 1, 'rotate (+80.88-175.2)*y', or else it was offset from the
wrapped ends. Using the start/end wrapping point to judge where the planet
surface features are when the camera is directly along -z (or +x if not
rotating away from the 0 degree longitudinal line) it makes it a little
tricky if that line isn't at zero.

Bob H.

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