Exploring the world of free tools for GIS, GPS, Google Earth, neogeography, and more.
Part three of this series (part one, part two).
Type: Freeware, open-source
Platform: Windows
Last update: 2007
Personal experience: Minimal
Description
Continue reading ‘The Big List Of Free GIS Programs - N Through R’
A continuation of this list from the first post.
Type: Freeware (formerly commercial), open-source
Platform: Windows
Last update: 2006?
Personal experience: Minimal
I plan to look at this one in greater detail in the future - looks like it has some really useful capabilities. Here’s a list of chapter titles from the Applications Guide to give you a feeling for what it can do:
Continue reading ‘The Big List Of Free GIS Programs - I Through M’
The backlog of topics for this blog continues to grow beyond my ability to keep up with it, and current work demands make it unlikely I’ll be able to catch up soon (though I should still be able to put up new posts at about the same rate). So I thought I’d do a quick set of posts on various types of GIS software, including both those that I have looked at in some detail, as well as those that I’ve given either a cursory look, or none at all. Let me know which ones I’ve missed, and I’ll add them to the list (and put up a separate post on them if warranted). I welcome comments on any of these programs, especially those I haven’t really posted on yet; if the comment is long enough, I’ll put it up as a full guest post. And I’m likely to come back to some of these in greater detail in the future.
Continue reading ‘The Big List Of Free Basic GIS Programs - A Through H’
GeoConverter: GeoConverter is an online front-end for ogr2ogr which lets you convert a limited number of vector file formats to each other. Free registration is required; while the registration page is currently in German the registration page is now available in English. Formats supported are:
You can convert to/from any of these formats except for KML, which is write-only currently. Formats with multiple files (e.g. shapefiles with .shp, .shx and .dbf files) require that all files to be upload are zipped up into a single file (100 MB max). I suspect the conversion system is Unix-based, which is usually happier with files that have no spaces in their filenames. Also worth remembering that certain formats like GPX and KML require the coordinates to be lat/long WGS84, so you’ll have to make sure your source data is in that coordinate system. I converted a fairly complex polygon shapefile into a KML file successfully, with the attributes written into the KML polygon properties, but there’s no ability to modify display based on attribute properties, as with shp2kml or Shape2Earth.
Thanks to Professor Stefan Keller, one of the creators of this utility, for the tip.
D2M Converter: A new online utility from Data2Map, currently in beta; free registration required. Converts from any of these formats:
to either Microsoft MapPoint (.ptm) or Google Earth (KML).
A few notes:
The service is still in beta, so it may have some quirks, but Data2Map has been very responsive to any issues I’ve encountered.
Zillow has released shapefile boundaries describing neighborhoods in 150 major cities, grouped by state. Available under the Creative Commons license, they’re free for general use in any application as long as you attribute Zillow as the source. Coverage is still limited; in Arizona, only the two largest urban areas (Phoenix and Tucson) are included. But Zillow encourages submissions of neighborhood boundaries for cities not currently covered in their database, and will work on including those submissions after they’re verified. Projection is geographic (latitude/longitude), NAD83.
Phoenix neighborhoods (created with the TatukGIS Viewer)
I’ve posted before about using OpenOffice’s Calc spreadsheet for use as a DBF editor (and why it doesn’t have the serious problem Excel 2003 has with editing DBF files). But Calc isn’t really designed to be a DBF file editor per se, which means that if, for example, you want to add new data columns to your shapefile’s DBF file, you’ll need to know a bit about column data formatting, and that’s kind of a pain. For basic DBF file editing, I find DBF Explorer easier to use, since it’s designed specifically and exclusively to work with DBF files. Adding and defining data column types is easy using the “Structure” button, as is modifying the values of individual data elements and searching for specific text elements (hint: use the Tab key to move to the data record you want to change). You can also delete full individual records, but that can easily screw up the relationship between the shape data and the associated DBF records, and should be done with care. Also be aware that the DBF file is updated continuously as you modify records, so if you want to keep the original unchanged, you should edit a copy of the original file.
Not a particularly fancy interface:
but it doesn’t need to be. And the help file tells you everything you need to know.
Addendum (1/29/08): Dave McGraw points out that if you use the “Structure” button to modify some of the parameters of an existing field, like the name, it will wipe out the data in that field, which is a bad thing; it will give you a warning first, though, that you may lose some data after such a modification. Other parameters, like field type and width, seem to be modifiable without nuking the original data; adding or deleting a field does not seem to cause any problems, either. Another argument in favor of editing a copy of the original, rather than the original itself.
The author also has some other free utilities on his site, including FTP/Web/Mail server software, and a simple install file builder.
Ever get an error message when opening a shapefile like, “Number of shapes does not match number of table records”? Yeah, well, neither have I. But if you ever do have such a problem, the Shape Checker utility might be able to rescue at least some, if not most of your data. It can re-generate a new .shx index file for your .shp file, add or delete lines to the .dbf file to match the number of shapes, and if your DBF file is totally hosed, can recreate a blank DBF for that shapefile. Not great, since you’ll lose whatever data you had in that datafile, but better than losing everything.
As the web page suggests, it’s probably best to do this on a copy of the corrupted file, rather than the original itself. Run the program:
Select the problematic .shp file with the left button, then recreate the .shx file with the “Build Shx” button. You can then check the DBF file for the proper number of records with the Check DBF button; if there are problems, or if the DBF file is missing, you’ll be given the option to fix it or create a blank one from scratch. I’ve tried it on point, line and polygon shapefiles I screwed up deliberately, and it worked as advertised. The program hasn’t been updated since 1999, but the author also provides the Delphi source code if you want to modify it yourself.
There are any number of ways to convert a digital elevation model (DEM) to shapefile vector contour lines, but most of the ones I’ve come across have had limitations of one sort or another. The best solution I’ve come across is the free program dem2topo; while it only supports a limited number of DEM formats, it has more flexibility in units and simplification than other methods, and the graphical interface is easy to use (unlike some command-line programs).
The program is written in IDL, an interpreted language, and you’ll have to download and install the IDL Virtual Machine first (free, but a 100 MB download, requires registration, and you may get a sales call). DEM formats supported are Canadian Digital Elevation Data (CDED), and nominally the GeoTiff format, but I’ve had some GeoTiff DEM rejected by the program for unknown reasons. NED GeoTiffs from the USGS Seamless Server work fine, and if you can open your DEM in the program 3DEM (which supports a number of DEM formats) and export it as a GeoTiff DEM from there, those should work with dem2topo as well. Once you’ve loaded your DEM into dem2topo:
you can choose contour intervals (meters or feet, regardless of what the original units were), the simplification factor (larger simplifies more, but at the cost of detail), whether to close the outer contours, and whether to display the contours as they’re being processed (for faster processing speed, leave these unchecked. More on these options is available in the helpfile.
Once configured, you have the option of converting the DEM into either shapefile contours, DXF contours, or into the .mp format used in creating maps for Garmin GPS units. For the shapefile format, major/intermediate/minor contour intervals are defined in the DBF file by the same hex code used in the .mp format: 0×0020 for minor contours, 0×0021 for intermediate, and 0×0022 for major . Processing speed will depend on the size of the DEM and level of detail, but don’t expect instant results. Converting the above 10-meter DEM to shapefile contours took well over an hour, albeit on my fairly pokey 2.4 GHz system; more memory also speeds up the process. But the results are worth the time; here’s a blow-up of the shapefile contour map of a very small section of this DEM:
A simple process, and if you run into problems, the help file is well done.
