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Archive for the '3DEM' Category Page 2 of 2

VRML Worlds Using 3DEM

At one time, Virtual Reality Markup Language (VRML) was going to be the next big thing on the Web; fully-interactive 3D environments were going to change the way we interacted with the Internet, and our computers. Didn’t quite work out that way – most people were on dial-up back then, which was too slow to make VRML practical. Even after broadband became more prevalent, it turned out that most people didn’t really want to interact with their computers that way. For displaying maps in an interactive 3D environment, Google Earth, World Wind, and other similar programs have pretty much supplanted VRML. But there may still be a place for it in some applications: you can use higher-resolution terrain than what’s currently available in Google Earth/WorldWind along with your own image overlays, the computing requirements are reduced, and the filesize for VRML worlds is usually pretty small. And you can get both stand-alone VRML viewers and browser plug-ins for multiple platforms for free.

3DEM makes creating a VRML world easy. From yesterday’s post, if you’re in a “Foreground” terrain view:


Select choose File=> Save VRML World; a file save dialog will open asking where you want to save the files. Next, you’ll be asked to specify some additional parameters for your VRML world:


Surface Smoothness and World Dimension set the effective resolution for your VRML world. Flat is less detailed than Smooth, and creates a smaller file size, but given the speed of modern computers, there’s little reason not to set Surface Smoothness and World Dimension to their maximum. Click OK, and two files will be created: an *.wrl file, which contains the terrain data, and a *.jpg file that contains the image data that overlays the terrain. You’ll need to keep both files together in the same folder when viewing the VRML world

To view the result, you’ll need a VRML viewer. Here’s a screenshot from GLView:

View of terrain and overlay in VRML

Using the controls in this program, I can walk or fly around the terrain, zoom in and out, change my viewing angle and altitude, take snapshots, and so on.

GLView is the best VRML viewer I’ve seen, but unfortunately it’s no longer available for public distribution. But there’s a good VRML browser plug-in called Cortona available for free from Parallel Graphics. There’s also a stand-alone VRML viewer available from Octaga, but I haven’t actually tried that one myself.

3D Perspective Views With 3DEM

The previous three posts on 3DEM have dealt with its capabilities on 2-D display of three-dimensional surfaces. But it’s also capable of producing three-dimensional images and animations. Not just standard perspective views, but a variety of animated and interactive views, both in standard and 3-D anaglyphic (red/blue) formats.

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Sea Level Rise, Storm Surge, And Flooding Effects Using 3DEM

Global warming is predicted to increase the sea level by:

  • About a meter over the next century in the best case (IPCC)
  • 5 meters if the rate of sea level rise continues to accelerate at the same rate it has since 1950 (Hansen)
  • As much as 12 meters in the worse case (melting/collapse of the Greenland and West Antarctic ice sheets) (Gore)

There is also reason to believe that it will increase the number and intensity of hurricanes, which in turn increases the likelihood of coastal flooding due to storm surges, wind and low pressure combining to drive ocean waters inland. And changes in weather patterns may result in increased flooding events. You can take a look at the potential effect of these events using 3DEM.

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Easy Map Relief Shading Using 3DEM

The Relief Shading website defines “shaded relief” as “a method for representing topography on maps in a natural, aesthetic, and intuitive manner”. A review of the many resources on that site, and on Tom Patterson’s excellent Shaded Relief website, will convince you quickly that getting the best possible results requires a great deal of knowledge, expertise and time. But you can get fairly satisfactory relief shading of your maps quickly and easily using 3DEM.

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DEM Terrain Depiction Using 3DEM

A DEM (digital elevation model) essentially consists of a grid of data, where every square in the grid corresponds to a geographic location, and the value at that position in the grid is the elevation above sea level. But those are just numbers, which are hard to visualize.

3DEM is a free program that opens DEM data and lets you visualize and use it in a number of different ways. It comes with a first-rate PDF manual, available from the Help menu. Today’s post deals with just the basics; upcoming posts will cover some of the interesting ways you can use the data to visualize topography and geography.

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