Author Topic: Problem with 3D rendering (Read 7002 times)

dumketu · « **on:** March 26, 2006, 05:54:54 AM »

I was trying to create a 3-D plot of a flight I took around Everest recently and discovered that there seems to be a problem with the way Topofusion deals with higher elevations in 3D mode. Basically it does not seem to render accurately above 25,000 feet. I first noticed this with Everest, then checked it with several other Himalayan peaks. Same result. To be sure it wasn't a region problem with the data I also checked it on the Andes and had the same result. I checked Mt. Mckinley, and there does not appear to be elevation data for there as it produced a flat 3-D image. I also tried Kilimanjaro and it resulted in a good rendering (it is just over 20,000 feet which leads me to the 25,000 or above conclusion).

BTW - topofusion makes some great 3-D images of the Himalyas with elevation data and landsat photos.

Brian

Krein · « **Reply #1 on:** March 26, 2006, 12:32:53 PM »

Interesting! I must say I've never tested TopoFusion above 25,000 feet.

'>

If you don't mind, I'd love to take a look at your data from the flight and it'll get me to debug the problem, too.

smorris@topofusion.com

dumketu · « **Reply #2 on:** March 27, 2006, 06:07:39 AM »

As luck would have it my GPS was set to wrap when full, so I ended up over-writing the flight with my great wall of China trek. I was using a GPS V, and didn't realize it has a much shorter track log than my e-trex vista. I had saved the track to mapsource on my laptop (which doesn't have topofusion) after my second day in China and I had not gotten around to moving it over to the computer w/topofusion.

'> So, I have a great track of the muytanyu section of the great wall, but no everest. I may go back next year so I'll have to try it again. I know that the everest track had a lot of breaks because of the airplane hull, my new GPSmap60csx should eliminate that problem.

dumketu · « **Reply #3 on:** April 06, 2006, 04:47:31 AM »

Well, I may have found the problem. I downloaded the 3' DEM files from the USGS seamless site and when I loaded it into 3DEM guess what - the data is full of "holes" corresponding to what should be the higher elevations of everest. The resulting 3d image is even stranger than using the auto-dem download. I also loaded some of the 1 km elevaton data which did not have the "holes" and everest looked great, although not as detailed.

I would be interested to know why the higher elevation data is not there in the DEM data.

Brian