Or from an oblique angle, looking in one direction:
Exploring the world of free tools for GIS, GPS, Google Earth, neogeography, and more.
Or from an oblique angle, looking in one direction:
I use to recommend the TatukGIS Viewer as a good free program for merging raster imagery and export it in georeferenced full resolution, but as last week’s post indicated, the latest version of it drops this functionality. Someone asked me for a recommended free alternative, and for now I’d pick MicroDEM for that. It does have some limitations:
The Portuguese chapter of the Association Of Volunteer Emergency Response Teams, in collaboration with Peter Guth and Donald Springer, is working to create a general-purpose set of symbols useful in mapping the position and condition of infrastructure, resources and incidents during emergency situations. You can download these Disaster Response Map Symbols as a True Type font from the DRMS website, along with a PDF file that documents the symbols There are 253 symbols depicting infrastructure, resources and incidents (graphic from the help file for MicroDEM, Peter Guth’s freeware GIS):
And additional dot symbols that represent the status of the higher-level symbol:
These status symbols would be plotted directly below the higher-level symbol, to indicates its condition/status:
Any GIS software that can use True Type fonts for symbols or labeling can use the DRMS symbol set directly. But MicroDEM has some special capabilities built in for working with this symbology. Make sure you’ve used the most recent program install, which includes the DRMS True-Type font; also, download the latest executable and copy it into the program directory.
From MicroDEM’s File => Tools menu, selecting Military icon generator brings up the icon composer window; make sure the DRMS tab is selected:
Double-click on an icon to select it, and then modify it as you like:
Once the symbol design is complete, you can save the symbol to the clipboard to paste into a graphics program, or choose “Save to file” to save it as a PNG, GIF, JPG, BMP or Targa format graphic file for those GIS programs that let you select graphic images to represent points.
You can also plot these symbols directly on a map in MicroDEM. Open up a georeferenced raster image in MicroDEM:
Clicking on the Map Annotation button on the toolbar (second from the left), choose Military icons from the drop-down, and then enter a filename to save the locations for the icons you want to place. You’ll then use the same Icon Composer interface as above to design your DRMS icons. The Left text is used as a feature ID in the DBF file, and also in the KML file you have the option of creating later on. Once you’ve designed your icon, you can double-click on the raster map to place the icon on that map:
Click on the “Close” button in the Icon Composer when you’re done. You can now export this map image directly to a generic image file or GeoTiff using the appropriate File => Save … option. But by right-clicking on the map, choosing Load => Google Earth overlay, you can export both the raster image and vector points to Google Earth. Here’s the raster overlay in Google Earth (vector overlay is turned off):
And here are the vector points, with the selected icons, for the same area (raster overlay turned off):
These data files are loaded into Google Earth automatically, but they’re not saved; to keep them for future use, right-click on the dataset listed in the Google Earth Places pane, choose “Save Place As”, then save it as a KMZ file.
Closing the Icon Composer will also open up a DBF table window with the locations of the points you’ve just created; you can convert that to a point shapefile by clicking on the Report button, then selecting point shapefile. There’s also an option with this Report to create a KML file, but make sure you save this KML file in an empty folder. As I found out by testing it, this option creates a KMZ file, copies every single file in that folder into the KMZ file, then deletes the original file from the folder. If this happens to you, rename the KMZ extension to ZIP, then use your favorite unzipping program to extract out the original files. Also, the KMZ file contains only the KML text data, which references the graphic icon files in a local directory on your computer for display in Google Earth. If you want to save this file for future use on your computer or another computer, and keep the graphics, you will need to open the file immediately in Google Earth, then save it as a KMZ file (right-click, choose “Save Place As”,etc.).
…would you know an easy (and free) way to query a DEM (Digital Elevation Model) to get elevations for a list of points (potentially as many as a few thousand)
Well, I know one way to do it with free software:
My visitation logs show a surprisingly large number of visitors interested in converters for the Military Grid Reference System (MGRS), the standard geocoordinate system used by members of the NATO Alliance. So I thought I’d do a quick roundup of previous links/posts related to MGRS, and then talk about another program that might be useful if you’re working in that coordinate system.
In a previous post, I used MicroDEM’s ability to create GIF Google Earth overlays with transparency to create selective overlays of MicroDEM terrain analysis products. But you can use this ability with any georeferenced raster image, including topo maps, as long as the areas of the graphic you want to have transparent are white. One example would be USGS 24K topo maps, but these often have large areas that aren’t white, as in this case:
In a previous post, I talked about using MicroDEM to easily create Google Earth ground overlays, images draped over Google Earth terrain in the correct position, like this terrain-shaded topo map (viewed in Google Earth):
But you can also create a Google Earth ground overlay in MicroDEM as a GIF with transparency, where any part of the image that’s white will be invisible in the Google Earth overlay. There are a number of MicroDEM analysis functions that can produce a graphic product with the data product in color and the background in white. One example would be the terrain category function, where you can select parts of terrain based on parameters like slope, elevation, aspect ratio, and relief. Suppose I have a DEM displayed in reflectance mode:
In Google Earth, a ground overlay is an image that’s been imported into the program and “draped” over terrain as a substitute for the default imagery. In the Free and Plus versions of Google Earth, you have to position the overlay manually to put it in the right geographical context, stretching and rotating it until it’s properly positioned. Google Earth Pro is able to open some kinds of georeferenced images (like GeoTiffs), and automatically drape them in the correct geographic position, but at $400 it’s not for everyone. The free GIS program MicroDEM has recently added the ability to automatically create a Google Earth overlay from any georeferenced image it can open, including GeoTiffs, and formats like JPEG and BMP if they have worldfiles associated with them