Hi all,
> Hi Paul,
>
> That new image helps quite a bit actually. The elevation
> values for your image are extremely strange. All of the
> values are negative except for the areas that are in the
> craters. I'm using OpenEV to inspect the values and it looks
> like the craters have extremely high positive values and the
> rest of your image has negative values.
>
> It seems as if the areas in the craters are NoData and are
> potentially not being specified correctly. I believe that
> osgTerrain will just use 0 for values that are NoData, which
> will typically result in small holes in the data that go
> *down* to 0. Since your actual elevation values are
> negative, the holes are going *up* to zero, which is why you
> see the plateaus.
>
> It seems to be that this is a problem with your data, not VPB.
I haven't examined the data to closely but I suggest the magic
is buried in the last line of the gdalinfo output
> > Band 1 Block=10240x1 Type=Int16, ColorInterp=Undefined
> > NoData Value=-32768
*************** *********
> > Offset: 1740000, Scale:0.6
*************** *********
HTH
Norman
>
> Hope this helps you track the issue down!
>
> Thanks!
>
> Jason
>
>
> On Fri, Apr 4, 2008 at 1:50 PM, Paul Brewster
> <[EMAIL PROTECTED]> wrote:
>
>
> Thanks Jason,
>
> I guess the geo info was lost when I rescaled the
> image. I'll include another GTiff with the info in it. The
> NODATA value is -32767, which is the smallest value possible,
> of course. I don't know the exact value of the bad areas,
> but if you look closely, you can see craters on top of the
> "plateaus", so I don't know if it is purely a NODATA problem.
>
> Thanks for the help.
>
> Paul
>
> Jason Beverage wrote:
>
>
> Hi Paul,
>
> I tried to take a look at the sample file you
> created, but it doesn't have any coordinate system attached
> to it so can't reproduce the problems you were seeing with that data.
>
> My gut feeling is that it has something to do
> with the handling of NODATA values in osgTerrain. What are
> the actual pixel values of the file you are using where the
> spikes are occurring?
>
> Thanks,
>
> Jason
>
>
> On Fri, Apr 4, 2008 at 10:29 AM, Paul Brewster
> <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>> wrote:
>
> Hey all,
>
> I'm using VPB to build some terrains and
> have found a few anomalies
> going on. I have a single 10240x10240 DEM
> of part of the moon in a
> 16-bit unsigned format. I can run gdalinfo
> and gdal_translate on it
> just fine, so I will include a 2.5% version
> of the DEM so that you
> can see
> what I am talking about. When I run "osgdem
> -l 1 --TERRAIN -d DEM.pds"
> everything works really well, except I get
> some areas in the terrain
> that just don't look right. My nice round
> craters suddenly jump out
> into plateaus in the middle. It appears
> that somebody put some
> monoliths in my moon craters. Does anybody
> know what is happening here?
> These anomalies are consistent throughout
> the levels, even if I
> go all
> the way down to full resolution. At first I
> thought these might be from
> signed/unsigned problems. But as I look at
> the data, I'm not convinced
> that is true. Anybody have any ideas what
> is going on? I'll include
> some pictures to show what I mean.
>
> Thanks for your help.
>
> Paul Brewster
>
> Oh, and here is the vital information:
> OpenSceneGraph: 2.3.5
> VirtualPlanetBuilder: 0.9.6
> GDAL: 1.5.0
> OS: CentOS 4.5 (linux)
>
> The header to my DEM:
> Driver: PDS/NASA Planetary Data System
> Files: LDEM20723Sm.LBL
> Size is 10240, 10240
> Coordinate System is:
> PROJCS["POLAR_STEREOGRAPHIC MOON",
> GEOGCS["GCS_MOON",
> DATUM["D_MOON",
>
> SPHEROID["MOON_polarRadius",1737400,0]],
> PRIMEM["Reference_Meridian",0],
> UNIT["degree",0.0174532925199433]],
> PROJECTION["Polar_Stereographic"],
> PARAMETER["latitude_of_origin",-90],
> PARAMETER["central_meridian",0],
> PARAMETER["scale_factor",1],
> PARAMETER["false_easting",0],
> PARAMETER["false_northing",0]]
> Origin = (29.614999890327454,-29.614999890327454)
> Pixel Size = (59.229999780654907,-59.229999780654907)
> Corner Coordinates:
> Upper Left ( 29.6149999, -29.6149999)
> Lower Left ( 29.615, -606544.813)
> Upper Right ( 606544.813, -29.615)
> Lower Right ( 606544.813, -606544.813)
> Center ( 303287.214, -303287.214)
> Band 1 Block=10240x1 Type=Int16,
> ColorInterp=Undefined
> NoData Value=-32768
> Offset: 1740000, Scale:0.6
>
>
>
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