Exploring the world of free tools for GIS, GPS, Google Earth, neogeography, and more.
Rich at GPS Tracklog cites OpenStreetMap’s recently-completed importation of the TIGER road data for the US, and challenges me to take a look at exporting it to a Garmin GPS (based on this post, I assume). OK, sure.
Continue reading ‘A Look At OpenStreetMap's TIGER Data Exported To A Garmin GPS’
Via the Kelly Lab Blog, the Berkeley/Penn Urban & Environmental Modeler’s Datakit has an enormous set of vector and raster data for the contiguous 48 US states:
Vector:
• Municipal, county, metropolitan area, and state boundaries, as assembled from the US Census Bureau’s 1990 and 2000 TIGER data.
• 1990 and 2000 census block and census tract boundaries and selected attributes, including net housing and population densities.
• Highway, railroad, and urban rail transit networks; and air and seaport locations as assembled from the U.S. Department of Transportation’s Bureau of Transportation Statistics.
• Locations of major employment centers and employment data for 1994 and 2003.
• Boundaries of all federal lands, including national parks and monuments, national forests, Bureau of Land Management lands, and military facilities.
• Locations of all major water bodies including rivers, streams, lakes, and reservoirs.
Raster:
• Municipal, county, metropolitan area, and state boundaries.
• Census block and census tract boundaries and selected attributes, including net housing and population densities (blocks) and population, housing, and demographic data (tracts).
• Boundaries of all federal lands, including national parks and monuments, national forests, Bureau of Land Management lands, and military facilities.
• Elevation and slope data generated from the National Elevation Dataset (NED).
• Comprehensive land cover data for 1992 and 2001 from the U.S. Geological Survey, including agriculture, forest, pasture, urban, and wetland locations.
• Locations of all major water body polygons, including lakes and reservoirs.
• Locations of lacustrine, palustrine, and riverine wetlands from the National Wetlands Inventory.
Data is in Lambert Conformal Conic NAD83 projection.
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.
Continue reading ‘Options For MGRS Coordinate Conversion And Viewing’
Prune is a Java-based GPS-track viewing and editing program that runs in Windows, Mac and Linux. When I last posted about it, the photo geotagging capability was a bit awkward – it required you to manually link a photo to a trackpoint, not automatically correlating trackpoints with photos based on time like most photo geotagging software. Version 4.1 is now out, and it now can automatically correlate and tag photos with data from a GPX track file. You need to have EXIFTool installed on your system; for Windows, put it the same folder as Prune, or into a system folder. Open a GPX track with File => Open Command, select either individual photos or an entire folder with File => Add Photos (or Photo => Add Photos). Select the photos you want to geotag in the file list at left, then select Photo => Correlate All Photos:
Prune lets you adjust for the time difference between the camera time and the GPS time (the former is usually the local time, the latter UTC). You can also set the correlation limits, i.e. how close the time or distance a trackpoint needs to be in order to be correlated with a picture. After correlating photos with track, you still have to select Photo => Save to EXIF to have the position data written into the picture’s data:
If you leave “Overwrite file” unchecked, the original will be saved with “_original” appended to the file extension; it would probably make more sense to append it to the filename instead, but that’s apparently a limitation of EXIFTool.
Another useful new feature in Prune is the ability to create a GPX file from an imported set of geotagged photos. Add the photos to the file list with the Photo => Add Photo command, select File => Export GPX, and Prune will create a GPX track file, connecting all the points where a photo was taken in the correct order.
Other new features in Prune:
Prune is released under GPL, and there’s a copy of the source code available for download. Not sure I would use Prune instead of GeoSetter for photo geotagging in Windows, but it looks like a great free alternative for Mac and Linux users, who have fewer free geotagging options.
Route Converter, covered in a previous post, is a program for editing GPS routes, and converting them from one format to another. The biggest complaint I had about the previous version is that it didn’t have a visual interface for viewing and editing routes. The program’s author writes to say that he’s now added a Google Maps interface that not only displays the route points, but lets you edit them within that interface:
Add, delete, and move points within the list using the buttons at right; they’re not directly labeled, but a popup label will show up when you hover over them with the mouse. Click on a position in the list, and that position will be shown in the Google Maps window with the red pin; click and drag to move that pin to wherever you want, and the position in the list updates automatically. To enter a position directly, or to change the point description, double-click on the appropriate field in the list to select it, and enter the new data.
Other new features include a few additional route formats and bug fixes. While it still doesn’t support as many formats as ITNConv, I now prefer RouteConverter’s interface. The version of RouteConverter described here is for Windows; the download page also includes versions for both Linux and Mac, but they’re labeled “experimental”, and “reduced functionality”, and I haven’t tried them myself.
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:
Continue reading ‘Creating "Transparent" Topo Map Overlays For Google Earth’
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:
Continue reading ‘Google Earth Ground Overlays With GIF Transparency’
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
Continue reading ‘Creating Google Earth Ground Overlays From Georeferenced Images’
