finding real coordinates in a DEM terrain.

[TheBadger]

Hey,

How might I overlay a map on a terrain built with a DEM? That is like a road map, for example? Is this something I would have to download with the data from USGS or earth viewer, or can I take something from google maps or google earth after the fact?

If I must download it when I take sat data, then what is the road map data map called in earth viewer / USGS? I mean to ask, which check box do I tick to get a typical looking road map?

And then, how do I add it to my TG terrain so that it correctly matches up with the terrain?

Thank you!

[RArcher]

You want the Geog Image Map Shader - http://planetside.co.uk/wiki/index.php?title=Geog_Image_Map_Shader

This will work with most georeferenced raster data and line it up with your georeferenced DEM file.  If you had a vector roadway file you would first need to turn it into a raster map and then load it.

[Oshyan]

1: You must find image/mask/map data with *georeferencing* information intact. This requires it be in a format that has georeferencing data, and that georef data be embedded in it. Most data from the USGS meets these criteria.

2: For vector data (most anything that is not height or aerial photos will be vector), you need to convert it to raster for TG to use it, as Ryan said. The caveat is that you must convert it *and maintain the goereferencing data*. This means converting to a common format such as GeoTIFF, and using a conversion program that will keep the georef data in the file.

3: This is the easy part. If you've done all the rest correctly, you have data that has embedded info to align it automatically. Just bring it into TG with a Geog Image Map Shader and it should align with any data of the same area that you have brought in with a Geog Heightfield Load.

So the trickiest bit of all this is stuff that unfortunately needs to be done outside TG. Global Mapper is great software for this, but fairly expensive and not Mac-compatible last I looked. There are other less friendly/easy options that are free and cross-platform, possibly Landserf, GRASS GIS, others...

- Oshyan

[TheBadger]

Thank you Ryan and Oshyan.

This is the next level for me. Once I have a way (including soft) that I can manage for this part of things, I feel like I will be in a good place. I dont feel like I need to be as good as some of you, but I do need to get to more of a middle ground.

Ryan,
Good to see a post from you man!

[TheBadger]

It is good that planetside improved and made simpler the process of using SAT data! Now these other things feel much more approachable than they did before.

After looking at the Landserf, GRASS GIS sites, I think GRASS GIS looks better supported. It does not look overwhelming to me in terms of how it works. And there are tuts. Landserf does not give enough info on its page to really form a view.

I will use the method Ryan posted for what this thread was about in the first. But I am downloading the other program too for later. There are a lot of things I want to try that I have posted questions about, and may now be able to pull off!

Thanks again.