USGS Data

[oliverz3d]

I'm encountering some scale and georeference issues in Terragen 2 from USGS data I've acquired from the new 2.0 National Map viewer. While the new viewer is in many ways easier to use than the old version, it introduces some issues, among them no more geotiff export as another thread already noted. So it seems one is stuck converting arcgrid data first. I looked into a few of the recommended solutions. I was unable to get the USGS provided conversion tools to work even though GDAL is installed and recognized; it strangely won't recognize the arcdata format from USGS. Landserf refuses to work with Java on my system, even though it's all updated. VTBuilder works, but I suspect it's producing the issues I'm encountering in Terragen.

Translating Arcgrid to a Terragen file in VTBuilder results in a 1m XY size heightfield. So I translated to a geotiff instead, which reads in at 10811m XY size in the heightfield load statistics field. That value however appears to be the number of vertices, not the actual size which is around 90000m XY. As a result, the height, is considerably stretched (though the values appear accurate) and need to be significantly reduced via the heightfield's displacement height multiplyer setting.

The segment I'm importing from the USGS is sizeable, approx 400 x 400km, so the data is delivered in several chunks and when two separate chunks were auto geo-referenced, they somehow end up on top of each other on the planet (note: I'm adjusting the camera, I haven't actually shifted the planet's apex to the imported terrain yet in Terragen) which would indicate an issue in the georeferencing from VT builder to Terragen.

I'm not sure how to proceed. As the USGS viewer is probably the biggest source of DEM data I can't be alone in experiencing these new conversion difficulties? Appreciate any help.

[jo]

Hi,

If you know the heights are correct in the TER file you're getting then you can use a Heightfield resize operator to resize the heightfield to its real world size. You can create a Heightfield resize node by selecting the heightfield shader in the Terrain node list and  choosing it "Heightfield resize" from the menu of the Add Operator button underneath. The way the node is set up default should work fine, just enter the correct size in the Re-size in metres fields.

I can't talk about it much just at the moment but a future version has much better DEM loading abilities.

GDAL should work to load the Arcgrid files BTW. You probably know this already but the file to load would be the one called "w001001.adf". I also found that the files were strangely named in the ZIP I got from the Map Viewer. For example the "w001001.adf" was called something like "NED_19314570\w001001.adf". I had problems until I renamed the file to just "w001001.adf". Slashes in filenames can't be good. I downloaded these DEMS some time ago though, it might have changed since then. If you have the GDAL command line tools installed try seeing if gdalinfo can load the files.

Regards,

Jo

[oliverz3d]

Thanks Jo. I also tried Global Mapper earlier and like VTBuilder it didn't convert the arcgrid georeferenced data and the pixel count ends up as the scale in Terragen, unless I'm missing an export setting.

I went back to GDAL and the USGS conversion tools and managed to get it to work. I had the right adf file all along, it just wasn't originally picking up the supplemental adf files from the directory that are provided with w001001.adf and as a result it gave back the file not recognized error. Now the size is correct in Terragen and it's correctly georeferenced. I also have terrain chunks seamlessly lined up.  I'd love to see streaming load capabilities of DEM files onto the planet in a future version of Terragen, much like what Chris West did with the Terrain plug-in for 3DS Max or GlobalMapper does with the orthoimagery.

[oliverz3d]

It seems the USGS 2.0 Viewer has new problems with orthoimagery files for texture mapping. Alot of the options have vanished: there's no Landsat for example. Just some staged color jpg2000's from local aerial flyovers that don't cover the entire space and dynamic NAIP UTM GeoTiff's which the USGS viewer indicates cover the entire area, but in actuality it covers only a very small portion at the center of the multiple arcgrid through ten images. I can view incredible satellite imagery through the separate USGS Landsat 7 Orthoimagery viewer site, but there's no apparent way to save out the data.

How are you all getting your textures now with the changes to the USGS system? I've been able to use Global Mapper to download an image from LandSat 7 matching and specifying the latitude/longitude bounds of an arcgrid unit, but there must be a way to access that same data that Global Mapper itself is accessing...

In Terragen 2, there also appears to be no way to have an image map shader use a non-elevation GeoTIFF positioned via georeferencing; or am I missing something? I've instead selected the corresponding terrain unit and at the center in the viewport, right clicked, copied the coordinates and pasted those into the image map shader position. However, that's dependent on the mouse cursor, so there's a slight degree of inaccuracy with the alignment. Perhaps there's another way of getting a completely accurate position center?

[jo]

Hi,

Unfortunately it's not possible to have images georeferenced at the moment. You need to enter the positions etc. manually. We realise that it's very useful to georeference images as well, however that's a bit further down the track than the DEM improvements I mentioned earlier. In some cases it should be easier to manually position images with the DEM improvements.

I'll make a note that you were interested in streaming DEM data.

Regards,

Jo

[TheBadger]

Hey Jo.

Since you guys said there is a good chance that the next update will include a bit of perks. Things like terrains and rocks and stuff. Would you also please consider making and providing some step by sep instructions for using satellite data correctly, with-in TG2.

Its not that its impossible to understand with out steps. Just I have found it difficult to keep track of all the right information. And most of whats here in the forum is, plainly speaking, unhelpful to me. The information is spread all over the place, and a good amount of it is incorrect/outdated.

I have been able to use sat data in a render. But I did not get the results I wanted. I expect that I did something wrong, used wrong/bad file kinds, or just missed a setting some place. I pretty much just gave up on that part of TG.

It seems to me that this technology changes pretty fast based on outdated links in the forum to data providers, or instructions in the forum that do not seem to match up with the data.
The data kinds also seem to change often, relative to the earliest posts I have read in the forums. There is also a ton of file extensions on the net for sat data. And its difficult for someone like me to know whats what. Not to mention that TG2 keeps improving and changing.

So a step by step for each data type used in TG showing how to correctly use data for best results would be sooooooo helpful.
It feels to me that being able to use this data in TG is one of the softs most powerful tools.  I really hope that some official guidance will be provided so everyone (mostly me) can take full advantage.

Thanks for thinking on it.

Sorry if this is a hijack, oliverz3d
But this is the most current thread on the subject.