DEMs (no this isn't political)

[StevenB]

It's been a long time since I played with DEMs to get digital data for a map. I used to work with MicroDEM with some success in RTII.

What data and readers are you map builders currently using

Thanks,
StevenB

[AZ Rail Rat]

Here's something I put together several years ago. Have not seen it for almost as long. Links might not even be good anymore. Never did finish it. Not the "preferred" way, just what I learned.

Might give you some ideas though.

http://www.users.qwest.net/%7Egreames/A ... ZRR%20Blog

[Wolverine@MSU]

I still use Microdem on the rare occasion that I need to build a heightmap. There's a new version available ( v 10) that will allow a color table with more than 256 colors (I think it will hold up to 1024), so you don't need the special version I have posted. If you need an elevation table I can post one. The newer version also makes it easy to merge DEMs, so if what you want covers more than one DEM, it's easy to merge the needed DEMs and then crop to the dataset you want for the final map.

The link to the Microdem Download page is here:

http://www.usna.edu/Users/oceano/pguth/ ... emdown.htm

[WPandP]

I do most of my image editing at work, where we have Macintoshes. Thus, I use "MacDEMPPC" in classic mode on Mac OS X... which I would not be able to do if I upgraded my iMac for a newer Intel-based machine (they won't run classic environment). It took me a while to figure out how to turn off the shading, though - where it places highlight and shadow to make it look bumpy onscreen. Can't use a shaded DEM as your height map, otherwise you get canyons on all the southeast sides of your hills!

I can't wait for the day when 3-D map utilities start to hook into Google Earth and give you not only elevations but actual aerial imagery for your base map, with just a few clicks... like a better version of RRT3's map maker.

[Wooly]

I have a DEM question too. I downloaded Microdem, but I am having trouble opening the DEM files I downloaded. Mircrodem V10 that I downloaded came with one DEM file already, Hanging Rock Canyon, CA, and the exact file name is HangRockCanyon_DEM_2.tar.gz. It opens fine in Microdem. I downloaded 2 DEM files from the USGS website (following the tutorial I found here at the forums), but they won't open. They are the same file types though, w140n40.tar.gz and w140n90.tar.gz, respectively. I can't figure out why they won't open. They are in the same folder with the map that works too. I know they are compressed files, but apparently that is the correct format for the maps. Any ideas?

I should add, that in the tutorial, the files in the DEM folder are .hdr files for "header". But it appears to be different in this version of Microderm.

[JoshM]

I downloaded the "GridFloat" in a zip file which has a .flt file that opened in microdem. Also I have a program called "mapbuilder.exe" that I think came on my CD which is more simplified method.

[Hawk]

Mapbuilder came on the original release of RRT3, the one with 2 cd's but it's not included in the current one cd release that can be found on the discount racks.
The current one cd release comes with the 1.05 patch but not the Coast to Coast Expansion.

[Wolverine@MSU]

I have a DEM question too. I downloaded Microdem, but I am having trouble opening the DEM files I downloaded. Mircrodem V10 that I downloaded came with one DEM file already, Hanging Rock Canyon, CA, and the exact file name is HangRockCanyon_DEM_2.tar.gz. It opens fine in Microdem. I downloaded 2 DEM files from the USGS website (following the tutorial I found here at the forums), but they won't open. They are the same file types though, w140n40.tar.gz and w140n90.tar.gz, respectively. I can't figure out why they won't open. They are in the same folder with the map that works too. I know they are compressed files, but apparently that is the correct format for the maps. Any ideas?

I should add, that in the tutorial, the files in the DEM folder are .hdr files for "header". But it appears to be different in this version of Microderm.

The ".tar.gz" is a UNIX compression system and I don't know if WinZip will handle them. Get WinImp and unzip them to their final stage, which should yield all the files fully uncompressed.

[Hawk]

WinZip will handle .tar.gz files fine. This shot is from Version 9.

Click on image to view full size

[Wooly]

Well you guys helped me with one area, but now I am stuck on another.

I unzipped my .gz file to a .tar file like was suggested to me. Then I unzipped the .tar file to get several files, including a .hdr file. That opens in Microdem, just like the tutorial says. I followed the tutorial and I resized a section of map that I wanted, and then I colored it. I saved it as a bitmap, and then as a .tga file, and then opened it as a new heightmap in the editor. But the map that opens has no physical relief...it's just a blank map.

I have had this happen with all 3 maps I have tried to make with Microdem, and I have had mixed results even doing simple shapes with MS Paint. I must be doing something wrong, and I am sure it's the coloring of the map to be used as a heightmap. I have played around and used different color parameters, including grayscale in Mircrodem.

Any suggestions?

[Wolverine@MSU]

You have to color it by using the "ELEV_COLORS_0-9999.dbf" file. The file can be found as part of the ZIP file here:

http://www.msu.edu/user/bowlby/rrt3/MD4RT3.zip

If this is the elevation color file you have been using then I don't have a clue why it isn't working. The colors should look like those in the tutorial:

http://www.msu.edu/user/bowlby/rrt3/tut ... orial1.htm

[Wooly]

Thanks Wolverine, that fixed it. I was using the wrong elvation color database file. I guess I missed the part about adding that specific .dbf file. Thanks for your help, and for your tutorial. I would have taken me a very long time to learn all of that myself.

[Hawk]

Question Wolvy - is the GTOPO30 the only data we can use for RRT3?

[Wolverine@MSU]

Question Wolvy - is the GTOPO30 the only data we can use for RRT3?

No, there are several data sets that are compatible with MICRODEM. There are some lower resolution data sets, as well as some sets that I think offer 1 meter resolution. I'm not sure what they are, but I think I remember them being some special satellite data. Anything that you can bring into MICRODEM should be suitable for generating a heightmap. Check the MICRODEM documentation for compatible data types. If I get some time (next week is Spring Break) I'll look into it.

[Hawk]

OK! Thanks!
I was looking through the latest version of Microdem and that's why that question came up. There is more detailed data available now, as you said-down to 1 meter resolution.

[Wooly]

Question Wolvy - is the GTOPO30 the only data we can use for RRT3?

Yeah, Wolverine answered it better than I could. There were several different databases at the USGS website, and I think Microdem can handle several of them. There was one called SRTM, which I think was better than GTOP30, but I think you had to pay to get that data. The GTOP30 was free, and it had a tutorial, so I have never tried anything else. I have been VERY pleased with the GTOP30 data and Microdem though. It was very easy to use and learn, and it gave fantasic results. Sometimes when I have a spare minute, I make a 3d map of someplace just for the fun of it (yea, I am a map nerd). It takes like 15 minutes to make a nice map.

The tutorial was INVALUABLE. I would have never picked it up fast without it, but once you use that, the program becomes pretty easy to navigate. I should add what I have learned about merging maps to go along with the tutorial. Not that I am an expert, but I noticed it was not in the tutorial, and (even thought it's pretty straight forward) someone might find it useful to have step by step instructions for merging data from different GTOP30 map sections.

[Wolverine@MSU]

Not that I am an expert, but I noticed it was not in the tutorial, and (even thought it's pretty straight forward) someone might find it useful to have step by step instructions for merging data from different GTOP30 map sections.

I'm pretty sure the newest version of Microdem will do this automatically, or at least there is a menu command for merging them when loading.

[Wooly]

Not that I am an expert, but I noticed it was not in the tutorial, and (even thought it's pretty straight forward) someone might find it useful to have step by step instructions for merging data from different GTOP30 map sections.

I'm pretty sure the newest version of Microdem will do this automatically, or at least there is a menu command for merging them when loading.

Oh yeah, it's a menu command, and pretty easy to do. I just thought that an exact step by step guide with a few pointers might be useful to some people.