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.
Archive for the 'DEM' Category Page 8 of 8
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.
Over the next few weeks/months, I’ll be putting up a fair number of posts on software tools that work with Digital Elevation Models, or DEMs for short. A DEM is essentially a grid of an area where each point in the grid represents the elevation or altitude at that point. With a DEM, you can do things like determine the altitude and slope at a point, measure the terrain profile, make 3D views (both static and interactive), and so on. Before starting those posts, it makes sense to talk about a good source for that data.
Continue reading ‘The USGS Seamless Data Distribution System’
OgleEarth posts about Hey, What’s That?, a website that lets you enter a location and then gives you:
- A panorama of what’s visible from that location, marking the position of peak geographic landmarks
- A list of the peaks, and the ability to show their position relative to your location on Google Maps
- Terrain profiles (elevation versus distance from the location to any point on the map)
- A plot all the areas visible from that location in red on Google Maps (aka the “viewshed” or “weapons fan”)
- Contour lines (zoom in for these)
- Google Earth export of position, viewshed, horizon line and horizon extent. If the viewshed area is large, this might strain the memory capacity of lesser systems.
It uses 30-meter SRTM version 1 data for its calculations, so there may be some quirks depending on whether there are holes in the SRTM coverage for your area. They’re switching over to SRTM version 2 soon, which is better but still not perfect. It only works in the US right now, but according to OgleEarth, they hope to expand coverage worldwide. A cool site! Check the OgleEarth posting for more info.