11 replies to this topic

[David Medeiros]

I need to create some contour lines from DEM data I have. In the past I've done this in Arc but my current Arc copy at work does not have the required extensions. Is there a cheap (or even free) Mac based software package that can do contours from raster elevation data?

[redbeard]

There are some, I'm mostly drawing a blank but I do believe QGIS does this with a plugin. If that doesn't work, I can generate some for you (this evening even), just let me know where. In the meantime, I'll try to remember what other packages does contours.
I use GlobalMapper for many things (except cartography) and it does do contours. It is Windows based.

I need to create some contour lines from DEM data I have. In the past I've done this in Arc but my current Arc copy at work does not have the required extensions. Is there a cheap (or even free) Mac based software package that can do contours from raster elevation data?

[David Medeiros]

There are some, I'm mostly drawing a blank but I do believe QGIS does this with a plugin. If that doesn't work, I can generate some for you (this evening even), just let me know where. In the meantime, I'll try to remember what other packages does contours.
I use GlobalMapper for many things (except cartography) and it does do contours. It is Windows based.

I need to create some contour lines from DEM data I have. In the past I've done this in Arc but my current Arc copy at work does not have the required extensions. Is there a cheap (or even free) Mac based software package that can do contours from raster elevation data?

I'll take a look at qGIS and see if that will work. This isn't pressing so I have time to experiment, though I may take you up the the conversion offer later if I can't find a good solution.

[Martin Gamache]

I'm sure GRASS can do this.

[redbeard]

I'm sure GRASS can do this.

It can.
r.contour
http://grass.itc.it/.../r.contour.html
But GRASS is difficult to learn when you're used to arcgis, and all you want is contours. Granted, GRASS is much more valuable to learn when you have a bigger project to do.
QGIS does interface with GRASS, so that is a plus.

[David Medeiros]

anybody ever use dem2topo? It requires an installation of IDL Virtual Machine. I don't know much about either.

http://people.uleth....d.gom/dem2topo/

[Peter Finch]

I need to create some contour lines from DEM data I have. In the past I've done this in Arc but my current Arc copy at work does not have the required extensions. Is there a cheap (or even free) Mac based software package that can do contours from raster elevation data?

If you are familiar with using the Mac terminal window you can do this with the GDAL command line utility GDAL_contour which outputs a shapefile as default.

http://www.gdal.org/gdal_contour.html
http://www.gdal.org/index.html

[David Medeiros]

FYI, I downloaded dem2topo and the IDL Virtual Machine and had a go at it. It works pretty well. THe interface is simple and easy to understand, it only does one thing (create contours from DEMs) which I like. It's designed to work primary with Canadian DEM files (CDED) and didn't like my USGS DEM's but it will run GeoTIFs form the seamless server. It's platform independent as well. It could be polished up a bit, the file location interface is a bot doggy, and I can't seem to get it to load without always assigning an application first.

Attached Files

•  Screen_shot_2010_05_27_at_8.24.05_AM.png   706.13K   54 downloads

[redbeard]

Looks good. I didn't zoom in too closely, but perhaps you can answer a few questions...
When you zoom in pretty good, are the lines angular or is there a bit of smoothing built in? If so, it is easy to adjust?
Performance - how does it do performance-wise? Can it handle a large area (ex: 1degx1deg or larger)?

FYI, I downloaded dem2topo and the IDL Virtual Machine and had a go at it. It works pretty well. THe interface is simple and easy to understand, it only does one thing (create contours from DEMs) which I like. It's designed to work primary with Canadian DEM files (CDED) and didn't like my USGS DEM's but it will run GeoTIFs form the seamless server. It's platform independent as well. It could be polished up a bit, the file location interface is a bot doggy, and I can't seem to get it to load without always assigning an application first.

[David Medeiros]

Looks good. I didn't zoom in too closely, but perhaps you can answer a few questions...
When you zoom in pretty good, are the lines angular or is there a bit of smoothing built in? If so, it is easy to adjust?
Performance - how does it do performance-wise? Can it handle a large area (ex: 1degx1deg or larger)?

FYI, I downloaded dem2topo and the IDL Virtual Machine and had a go at it. It works pretty well. THe interface is simple and easy to understand, it only does one thing (create contours from DEMs) which I like. It's designed to work primary with Canadian DEM files (CDED) and didn't like my USGS DEM's but it will run GeoTIFs form the seamless server. It's platform independent as well. It could be polished up a bit, the file location interface is a bot doggy, and I can't seem to get it to load without always assigning an application first.

Performance was pretty good, it did 100' main and 500' index contours on 3500' of elevation (around 800 contour features in all) in an area roughly 45' x 44' in about 4 - 5 minutes. You can supposedly do multiple adjacent DEMs and output a seamless contour .shp file.

I used the default program simplification value and got vectors with very tightly spaced anchor points, all straight line segments. I used the simplify command in Illustrator to thin it down and convert to smooth curves. I'm relatively impressed, it did well for free.

[Charles Syrett]

Performance was pretty good, it did 100' main and 500' index contours on 3500' of elevation (around 800 contour features in all) in an area roughly 45' x 44' in about 4 - 5 minutes. You can supposedly do multiple adjacent DEMs and output a seamless contour .shp file.

I used the default program simplification value and got vectors with very tightly spaced anchor points, all straight line segments. I used the simplify command in Illustrator to thin it down and convert to smooth curves. I'm relatively impressed, it did well for free.

And the shaded relief? Photoshop?

Charles Syrett
Map Graphics
http://www.mapgraphics.com

[David Medeiros]

Shaded relief is done in Natural Scene Designer and finished in PhotoShop before importing to MAPub.

This is a section of a map that I have posted here before but without contours and a poor relief image. I've been playing around with my relief techniques and decided to redo this map. I'll re-post the whole thing eventually.