L3DT Users' Community

Hay aaron,

OK a quick questain. If I was to say import in a terrain or "Sattelite data", say like the painted desert, would the information of the date that you cant see from above translate to mesh?
EXAMPLE: table rock is a thinner spier with a huge flat rock sitting on the top. would that show in this program and catch that data? Or Say a huge archway like you see in deserts that have been wind swept, would the date translate so you would see that when exported out?

I was thinking that maybe soundwaves/sonar in the data set would carry that info? I think it is out there somewhere. Just a questain for it has never been done in the private sector that I know of. But I am sure the .GOV boys are doing stuff like that.

Maybe PhotoGrametry DEV, using more data? I don't know it was just a questain. I have been wanting to do stuff like that for years in 3d other then model them and place them in the scene, that gets boring and not as acurate as I had in mind. Remember I am a artist not a programmer so I may ask stupid questains some times. But it seemed like a good questain to me so I ask it, HAHAhahaha

Thanks for letting the peanut gallery have a say /wink

DeathTwister
PS: if spelling bad I just woke up sorry, need more coffee!!!!!!

Hi DeathTwister,

OK a quick question. If I was to say import in a terrain or satellite data, say like the painted desert, would the information of the data that you can't see from above translate to mesh?

No satellite data that I know of contains topologically complex shapes like arches. This sort of data can't be represented by a 'heightfield', which is a data-structure used by DEM files, L3DT, and most other terrain programs. So, basically, if you can find a data file that contains this data, L3DT could not read it.

I was thinking that maybe soundwaves/sonar in the data set would carry that info? I think it is out there somewhere. Just a question for it has never been done in the private sector that I know of. But I am sure the .GOV boys are doing stuff like that.

I would be surprised if this sort of data didn't exist, at least for certain parts of the planet, but I'd be very surprised if it was available for civilian use. The resolution of such data would necessarily be very fine (i.e. <1m or so), which means the .mil guys and gals would be very unlikely to share. I'd say the best public data we'll have for quite a while is the 8.5m SRTM DEM data.

Cheers,
Aaron.

Edit: Err, that should be 30m SRTM data. The 8.5m data I was thinking of was from aerial LIDAR, is not in fact freely available, and nor does it cover much of the earth's surface.

Hay Aaron,

Ok I figured as much, but hay it never hurts to ask /smile.

DeathTwister

Actually there's 3M data for parts of Washington (St. Helens, Pueget Sound) and Texas (Dallas). So *that* is most likely the best we'll get for quite some time. It's really impressive stuff, you can see housing developments, roads, etc. But of course the level of detail has nothing to do with being able to store more than one altitude value for a given point, which is the limitation that keeps heightfields from being able to represent arches, etc.

- Oshyan

Hi Oshyan,

Care to shoot us a link to the 3-metre data? Sounds rather interesting.

But of course the level of detail has nothing to do with being able to store more than one altitude value for a given point, which is the limitation that keeps heightfields from being able to represent arches, etc.

No indeed, topology strikes again - you'd have to use a mesh or voxel based approach, I would suppose. However, my point was that for a survey to map any such features (regardless of how the data is represented) it must necessarily have sufficient accuracy to resolve them, which would mean something of the order of a metre to be useful.

Cheers,
Aaron.

Very true re: needed accuracy for overhangs/arches, etc.

The 3m data is available from the free, worldwide seamless data viewer/downloader at http://seamless.usgs.gov/ I use Global Mapper to convert and it works fantastically. To get the 3m data you want to select 1/9 NED in the Download panel of the data selector (right side of the applet). Note that, as I said, the area of availability is extremely limited. Last I checked it was only 2 areas of Washington (St. Helens and Pueget Sound) and Dallas, Texas. I will look again later on tonight to see if they've expanded it.

Fortunately you can see much of the detail in the online viewer if you zoom in close enough. Check out the amazing lava and flow shapes in the St. Helens data (even a parking lot for a visitor's center), or in Dallas you can "fly" over housing developments, etc. Pretty cool.

Also note that I've converted the St. Helens data and done some post-processing on it to remove some stitching and other artifacts. I've also converted to UTM, which I believe is more accurate as far as the real world goes. The data is in .ter format and is available in many sizes, from full-size 8193x8193 down to 513x513. You can find the downloads at Ashundar here:
http://www.ashundar.com/list.php?c=ter6

Edit: interesting, there are some more 3m data areas now. Some of the data appears to have some serious artifacts that virtually negate the 3m advantage. And anyway who really wants to see Lincoln, Nebraska in 3m? lol. There's some pretty impressive terrain in southern West Virgina though, including a small part of the Appalachian chain. Man that's a weird mountain range! Look at those long ridges...

- Oshyan

Hello,

Thanks a bunch for the info Oshyan. I've updated the data/resource downloads section on the links page to list the USGS site and the Ashundar downloads page.

http://www.bundysoft.com/wiki/doku.php?id=links

Cheers,
Aaron.

My pleasure. I love seeing what people can do with this level of detail in their data.

- Oshyan