Author Topic: Feature request: compress DEMs (Read 5817 times)

KanyonKris · « **on:** December 07, 2004, 09:26:30 AM »

With the (fairly) new 3D features in TopoFusion, I'm starting to collect a good set of DEM files. While hard disk space is cheap these days, at close to 10 MB per "quad" I already have more DEM data than map tile data. A while ago I ZIPed up a few DEM files to send to a friend and noticed that they compress pretty good - down to 2-3 MB or so. I'd like TopoFusion to compress DEM files - either as an option or standard - unless it would slow down TF too much to do the decompression.

Krein · « **Reply #1 on:** December 26, 2004, 09:43:17 PM »

It probably wouldn't slow down TF too much, but it would take some slow development time.

With the (soon to be released) NASA server capabilities, we are looking at automatic downloading of elevation data, which could make standard DEM files a bit obsolete.

The 3D data would all go into a 3dmaps.dat file, which I suppose could be compressed. We haven't worked out the details of this yet.

KanyonKris · « **Reply #2 on:** December 28, 2004, 01:44:43 PM »

For compression, you could use the free (of cost and patents) zlib (source and DLL available).

Pulling elevation data from a server sounds nifty. I'd like to read up on this NASA server and dataset, is it the Shuttle Radar Topography Mission data?

It would be nice if TopoFusion continued to support DEMs - especially if there might be holes in the elevation data from the server.

Thanks for the reply!

jmstacey · « **Reply #3 on:** January 11, 2005, 09:43:52 PM »

What is the time-table we could be looking at?
Along with this new capability, new and easier to obtain data, would 3d digital shading of topo maps by TopoFusion be possible?
For an entire map and not by block.
For example, 3d shaded topo maps that look like the National Geographic, or near to them?

When printed they look vitually store bought. (at least on my printer ':p'

)

Krein · « **Reply #4 on:** January 12, 2005, 07:18:54 PM »

Time table - possibly soon. I'm working on the basic version now.

We'll still continue to support DEMs, yes.

Shaded relief -- possibly, but that will be a ways off. It would be nice but we have other things to work on first.

gtc · « **Reply #5 on:** February 01, 2005, 04:52:49 PM »

If your file system is NTFS, you can compress the files automatically by right clicking the DEM file, selecting Properties from the context menu, clicking the advanced button, and then checking the compress button.

If you put your DEMs in a subfolder, you can right click on that folder, as above, slect Apply, and then also choose to apply the changes to all files and subdirectories.

I did this and got about a 50% reduction in files sizes on the disk. (You can check this by just hitting Apply rather than OK when you compress, or right clicking for Properties after you compress the file(s).)