HI Paul,
VPB is built around working on earth data, hence the default to WGS84.
You can override the size of the spheriod via --radius-equator value
and --radius-polar value, a recent bug fix to VPB fixed this
functionality so it should work now. It should also be possible to
set the coordinate string for the output, but... I have to admit I
haven't tested anything other than earth based data - to start I only
have had earth data to work with so far and it's been the focus of the
work.
As for non the coordinate system the data is in causing problems,
again I've never had such data before so can't really provide any
guidance on whether GDAL can cope with it.
VPB should be able to handle what you after, but there is good chance
that we'll need to tweak it a bit to achieve it. What bits we need to
tweak I can't say off hand as.. again I have no experience with this
type of data. Would it be possible for you to post an example dataset
and the VPB options that you are using?
Robert.
On Thu, May 29, 2008 at 9:59 PM, Paul Brewster [EMAIL PROTECTED] wrote:
Hey all,
I have a couple questions about VPB. I've been playing around with it for
about a month now, and have reached as far as I can go. After some help
from here a month ago (thanks all) I spent some time digging through the
source code to see what I could find and have reached about as far as I can
go by myself. It appears that I am trying to do something that VPB does not
support yet. I was hoping I could find a simple change to do what I want,
but it doesn't appear to be that easy. Or at least, my mind couldn't get
around the code enough to figure it out. Anyway, here are my
questions/concerns:
1) I am trying to do a model of the Moon. I have data in PDS format that
reads into GDAL just fine. I can run osgdem -l 1 -d foo.pds -o bar.ive and
it works fine. If I peek at the resulting ive file, I can see it has a
CoordinateSystemNode at the top with the right WKT in it. There is no
Ellipsoid because the terrain is flat. And a quick look at the vertices
seem to put them in the right area (uses moon radius, not Earth radius).
But I really need to do a spherical model of the Moon, since I am doing
Lander simulations and things like that matter. The only way I know to make
a spherical terrain is to use the --geocentric command. After tracing all
over the code, it appears that this forces VPB to use the WGS84 coordinate
system, no matter what else I try. When the intermediate and destination
coordinate systems are created, it automatically creates the default WGS84
coordinate system with appropriate Ellipsoids, no matter what the input data
is. So no matter how I try, I always get an Earth-like Ellipsoid with WGS84
coordinate system in my output. Am I doing something wrong? Is there a
command-line to indicate what I want the final coordinate system to be? I
have a WKT for the moon. Is there a way to force that? I tried entering
that WKT in, but it was never used for creating the intermediate and
destination data sets.
2) My data is in a Polar Stereographic projection, rather than a
cylindrical type projection. Which means that the center of the image is
the North (or South) Pole. Lat lines radially extend from the center and
Lon-lines are concentric rings around the center. When I use this on for a
--geocentric data set, it shows up as a partial wedge or orange slice
from the north pole to about 75 degrees North. It appears to me that it is
being treated like a cylindrical projection. I have not looked into this
problem as much. Is this a GDAL issue? Where does the projection from a
given pixel to a Lat-Lon happen?
Anyway, thanks for the help. VPB is a pretty amazing piece of software.
I've been able to do huge datasets quickly and easily, so I'm really
excited to get it working on the Moon too. I appreciate any help.
Paul Brewster
Data Visualization and Analysis Lab
NASA Langley Research Center
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