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Archive for the 'DEM' Category Page 7 of 8

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Elevation Profile In Google Maps

Published by
Leszek Pawlowicz
 in DEM and Google Maps. 2 Comments

Once again via Ogle Earth, a nifty little tool called Elevation Mapper. Enter two positions in Google Maps, either by typing them in or clicking on the map, and get an elevation profile between the two:

Getting an elevation profile using a Google Maps interface

Counterintuitively, the “flat Earth” box needs to be checked for this to work.

If you have a DEM (digital elevation model) for an area, you can create a similar profile using 3DEM, either for a straight line or an arbitrary line/GPS track. With a high-resolution DEM, this would give you a more accurate profile.




Can You Use GPS Data To Make A DEM?

Published by
Leszek Pawlowicz
 in DEM and GPS. 7 Comments

A reader from New Zealand writes, “I’m looking for a tool that will assist in the production of 3d terrain models from GPS elevation and track data. Ideally I would be able to walk over the land and generate continuous track data that could then be used to build a 3d mesh with the ability to refine it over time, fill in areas with higher detail. What is the best tool (in your opinion) for achieving something like this?” Can’t think of a single tool off the top of my head, but several ideas for possible approaches to handling this kind of data come to mind. But while this might be a good idea conceptually, it relies on the assumption that you can get accurate, consistent, repeatable position and altitude data from a GPS. And that’s not a good assumption.

Continue reading ‘Can You Use GPS Data To Make A DEM?’




Animated Flybys Using 3DEM

Published by
Leszek Pawlowicz
 in 3DEM, DEM and Google Earth. Closed

There’s one last feature in 3DEM I want to talk about: the ability to create animated fly-bys over terrain, with or without an image overlay. Doing a comparable animation with Google Earth requires either the expensive Pro version, or a copy of FRAPS for $37. While 3DEM’s animations aren’t as fancy as the ones you can get with Google Earth, they’re pretty good.

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Free Digital Geographic Data For Canada

Published by
Leszek Pawlowicz
 in data, DEM, GIS and topographic maps. Closed

The Map Room posts on GeoGratis, the Canadian Government’s new web gateway for free geographic data, both raster (topo maps, satellite images, etc.) and vector (hypsographic, political, etc.). No DEM (digital elevation model here), but you can get 90-meter data for Canada from the Geobase website or the USGS Seamless Server.




GPS Track Elevation Profiles With 3DEM

Published by
Leszek Pawlowicz
 in 3DEM, DEM, GPS and GPX. 1 Comment

3DEM ostensibly comes with a number of GPS interface capabilities, including the ability to download waypoints, routes, and tracks, and upload waypoints created in the program. I say ostensibly because I could only get one of the features to work with my Garmin 60Cx, downloading tracks; maybe you might be able to get more to work with your GPS model. But even that one feature allows you to do something more than just display the track on top of a terrain image: it lets you see the elevation profile for the entire track.

Continue reading ‘GPS Track Elevation Profiles With 3DEM’




VRML Worlds Using 3DEM

Published by
Leszek Pawlowicz
 in 3DEM and DEM. Closed

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:

3dscene1

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:

vrmlparameters

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

Published by
Leszek Pawlowicz
 in 3DEM and DEM. Closed

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

Published by
Leszek Pawlowicz
 in 3DEM, DEM, global warming and Google Maps. 3 Comments

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.

Continue reading ‘Sea Level Rise, Storm Surge, And Flooding Effects Using 3DEM’




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