SDTS files are the new standard for DEM's. These files are similar to regular DEM's but with a few exceptions. Compressed files of this type will have a .gz or .tar.gz extension. Bryce 4 will import these with the .DDF extension.
Scroll down the US GeoData page until you see the section shown at left.
Select the FTP link of your choice and choose a file for download.
I again chose FTP via Alphabetical List and then went to the letter "G". I was searching for Grand Canyon AZ, found the link and clicked on it. On the following page I saw the file 188.8.131.528243.tar.gz listed. This file was then downloaded and saved to my hard drive.
» Download the file without leaving this page by clicking here. [If you have problems downloading the file, you may need to right click the link and "Save As".]
However when I tried to decompress it on my PC, WinZip told me that the file was named 30_1_1_1218243_tar.gz. I continued.....but decompression was a disaster!
Do you see the difference? The original filename ends in .tar.gz and the downloaded file ends with _tar.gz.
Before attempting to decompress again, I had to rename the file extension [i.e., 30_1_1_1218243.tar.gz] so that it would decompress correctly. When I did that, I got a list of 18 .DDF files.
See the example below.
On a Mac, it's a little bit easier. You just decompress into a folder and save. When you look, you should only see one file.....however all 18 files actually reside in that folder.
Importing the file is almost identical to the instructions for the regular DEM's. Open Bryce, select the File Menu and click on Import Object. Then locate & select the file named "****CATD.DDF" [see image above] and wait for Bryce to process the entire SDTS data set.
IMPORTANT TIPS Just remember all 18 files are one SDTS data set. All files in the set must reside in the same folder. Do not rename any of the individual files.
On the USGS website, there are STDS Digital Line Graphs (DLG's). Bryce 4 does not currently support these types of files.