A 153MB DEM

Started by Costaud, January 30, 2008, 05:55:59 pm

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Costaud

Yes a DEM of Hawaii...153MB  http://www.soest.hawaii.edu/coasts/data/hawaii/dem.html but I'm unable to open it with 3DEM I get an memory error message.

old_blaggard

At 153MB, I'm not surprised....
http://www.terragen.org - A great Terragen resource with models, contests, galleries, and forums.

Oshyan

Big sucker. I recommend GlobalMapper http://www.globalmapper.com/ for working with higher resolution data sets. It's a bit pricey, but it's the best DEM tool around. :)

- Oshyan

gregsandor

I recommend Microdem for large datasets.  It is excellent, the author updates it continually, and it is free.

http://www.usna.edu/Users/oceano/pguth/website/microdem.htm

bigben

The resolution is 10m, so you can also download it in smaller chunks from the USGS http://seamless.usgs.gov/website/seamless/viewer.htm

And as most of the islands are under water you can combine this data with SRTM30 Plus http://topex.ucsd.edu/WWW_html/srtm30_plus.html or CleanTOPO2 http://www.shadedrelief.com/cleantopo2/ (post-processed version of SRTM30 Plus)

rcallicotte

Wow.  What a bunch of genius geeks.   ;D

Thanks.
So this is Disney World.  Can we live here?

Costaud

Quote from: gregsandor on January 31, 2008, 06:51:33 am
I recommend Microdem for large datasets.  It is excellent, the author updates it continually, and it is free.

http://www.usna.edu/Users/oceano/pguth/website/microdem.htm


Yes Microdem work for large DEM file but it does not export Terragen terrain like 3DEM.

bigben

February 01, 2008, 04:04:00 am #7 Last Edit: February 01, 2008, 04:06:45 am by bigben
When I was using an old version of GlobalMapper, I got around the TER size limit by exporting a geotiff of just the required area and then loading that into 3DEM to convert to TER.  There are a few limitations to this method but for most people's usage it works reasonably well.  I haven't used Microdem but it would be a surprise if it couldn't export geotiff

Quote from: calico on January 31, 2008, 08:37:08 am
Wow.  What a bunch of genius geeks.   ;D

Thanks.


Nah.. just geeks   :P  ;)

gregsandor

February 01, 2008, 08:19:30 am #8 Last Edit: February 01, 2008, 08:31:19 am by gregsandor
Microdem can subsample large dems and export as Geotiff.  Also you can georeference imagery, crop to the model, and export that as Geotiff with the references intact.  I particularly like its merge capablilities:  I modeled the Valley of Mexico and Tenochtitlan on a 1km dem base, overlaid with 90m elevation model, and for the immediate area of interest, 30m dem.  120 square kilometers modeled from different large datasets for a final dem of 4097 x 4097. 


bigben

Great stuff... looks like it's certainly a good alternative. 

A mix of resolutions is good for reducing memory usage, but if you have the RAM, disk space and data then you might as well make the entire terrain as high a resolution as possible as the final TER file size will still be the same. My old workflow of creating geotiffs in GlobalMapper (v4.7) and then converting these to TERs using 3DEMs could also be done with Microdem.

The only problem I had was with 3DEM. I was using UTM projection to allow for easy tiling of TER files and creating different resolution TERs. When I got to my larger, low res terrains I eventually ran into problems when the coordinates were too far out of the range handled by 3DEM (e.g. very large negative coordinates for terrains spreading across more than one UTM zone) 

My Swiss Alps terrain set was the first one to highlight this problem. I had to use a UTM zone closer to the western edge of the Alps in order to be able to extend the terrain to include the UK. With a direct export to TER (of any size) from the new version of Globalmapper that problem went away. I also found the final TERs were a bit cleaner without the intermediate conversion step but this is certainly a pretty good (free) alternative.