In a previous post, MicroDEM was used to determine when the sun was visible from a particular location for any day of the year, including blockage by topography. But MicroDEM can also assess that data for a number of contiguous locations, determine for each of them how much sunlight they get during the day, and create a map of that total daily insolation. In a sense, it can create a solar “viewshed” map for a specific area. That might be of interest to solar energy enthusiasts, or those studying plant/animal microhabitats.
Continue reading ‘How Much Sun Does That Spot Get - Plotting Solar "Viewsheds"’
An earlier post described how to use MicroDEM in conjunction with Trimble’s Planning Software to assess the effects of GPS satellite signal blockage by topography on GPS position error. But MicroDEM also has a built-in function that lets you calculate the times of day when the sun is blocked by the local terrain, and when it’s visible. Handy for photographers looking to shoot in sunlit conditions, campers who’d prefer shade early in the morning, and so on.
Continue reading ‘Determining Sun Blockage By Topography’
JS writes, “I am doing a very small wireless operation in Catalonia, and it would be very interesting to have the coverage map of the antennas. Do you know any free (or cheap) tools to do that and place it on Google Earth?” I know of two free Windows tools useful in analyzing radio coverage. The first one is a general purpose terrain analysis program that will give “quick and dirty” plots of line-of-sight coverage and required antenna heights fairly easily. The second, more sophisticated program is specifically designed for determining broadcast coverage and signal strengths, but is also more difficult to use. Getting the data products into Google Earth can take some work, but can be done.
Continue reading ‘Mapping Radio Coverage, And Viewing It In Google Earth’
A while back, I did a post on assessing the effects of sea level rise on coastlines using the program 3DEM. Here’s a terrain image of southern Manhattan Island at current sea level:
And here’s what it would look like with 8 meters of flooding, due either to a hurricane storm surge or global-warming-induced sea level rise:
The problem with the latter image is that 3DEM did a basin flood, i.e. it filled in all the terrain that was less than 8 meters below sea level, without taking topography into account. For example, a range of hills could lie between some lowlands and the sea, but 3DEM wouldn’t take that natural dam into account. But I also posted an animated flooding map of the same area that did take that terrain blocking into account (click on the “play” button to view the animation):
Today’s post will show how to create such a flooding animation.
Continue reading ‘Animated Flooding Maps - Storm Surge, Sea Level Rise And River Flooding’
Yesterday’s post dealt with Trimble’s Planning Software, which lets you calculate a GPS-satellite-geometry-dependent error parameter called “Dilution Of Precision”, DOP for short. The calculated DOP can tell you when the GPS satellite geometry is favorable (or unfavorable) for reducing errors due to GPS satellite geometry. But those calculations assumed that you had an unobstructed view of the entire sky, and had line-of-sight to every GPS satellite above the horizon. In many cases, though, your view of GPS satellites is likely to be obscured, either by local obstacles like buildings and vegetation or more distant ones like topography. There’s not much you can do about taking the former into account, but there is a way to deal with the latter to some degree.
Continue reading ‘Determining Terrain Effects On GPS Accuracy’
Previous posts have shown how to display parameters such as elevation, slope, and aspect in MicroDEM on a “global basis”, plotting these parameters individually across an entire DEM. But it’s also be useful to show which areas on a DEM fit within a specific range of values for these parameters, e.g. what areas have a slope greater than 50% but less than 100%. MicroDEM can do this kind of terrain categorization.
Continue reading ‘Selecting Areas Based On Terrain Categories And Values: Slope, Elevation, Aspect And Relief’
In addition to displaying elevation directly, either as terrain or colors, MicroDEM can also display elevation derivatives. Examples include curvature, relief, summits and ridges, but the simplest are probably slope and aspect.
Continue reading ‘Terrain Slope/Aspect Display And Analysis’
In earlier posts on MicroDEM, the digital elevation model (DEM) has been displayed in reflectance mode, terrain illuminated by light coming from an angle. But it’s also possible to display the elevations as different colors for use as a background image for maps, or for shading.
Continue reading ‘Elevation And Contour Line Display In MicroDEM - Make Your Own Simple Topo Maps’
