Author Archives: leigh
TriMet, the Tri-County Metropolitan Transportation District, serving Washington, Multnomah, and Clackamas counties in Oregon, is a leader in open source technology. They still use ESRI desktop applications, but they are using open technologies, including PostGIS and OpenLayers, to power their web services. Article: http://www.govtech.com/e-government/Open-Source-Software-Oregon-Transportation.html Share this:EmailFacebook
If you’ve ever needed to export a shapefile or feature class to a GeoJSON text file, there’s a handy ESRI-supported Python script available. It’s easy to install into your ArcToolbox, and works quite well: http://arcscripts.esri.com/details.asp?dbid=15545 So what is GeoJSON? JSON stands for JavaScript Object Notation, an encoding format for web object data. GeoJSON is just […]
Dr. Matthew Wilson, a Geography professor at Ball State University (Indiana) recently posted a reading list for critical GIS. What exactly is critical GIS? It’s not a synonym for emergency GIS. What Dr. Wilson actually means is critical thinking about GIS – not how to use GIS, but why to use GIS. The list is […]
The hypsometric contour interval on the classic USGS quadrangle maps is 40 feet. Although it’s not a nice round number, I think it looks fantastic at that scale. It’s good at representing many different terrain types. Which is why USGS contours have become a bit of a standard for many GIS and cartographic applications. But […]
One source of data that I feel is under-utilized is the USGS Board of Geographic Names. The BGN is a (mostly) comprehensive list of definitive feature names, covering most of the United States. The features are organized by state, by county, and by feature type, and each one has a latitude and a longitude. The […]
If you ever get the opportunity to work with bathymetric data, you may encounter CARIS files. CARIS is an enterprise GIS suite that is well suited to marine and hydrographic applications. Many GIS offices don’t have access to CARIS, but that doesn’t mean the data is out of your reach. CARIS offers a free data […]
As a spatial professional, projections and geodesy have become second nature to me – often to a point that I take them for granted. In many cases, the projection becomes like a font in a presentation – if you used Helvetica on page one, you had better use it on page two. Generally, the consistency […]
PostGIS is a wonderful suite of tools, which really anchors the open source web mapping toolkit. However, it doesn’t always integrate well with an ArcGIS desktop environment. One obvious source of conflict relates to projections – most of ArcGIS’s projections are infinitesimally different than their real world counterparts. As an example, consider the Washington North […]
In my previous post, “When Scale Bars Lie”, I mentioned the dangerous things that can happen when the map unit is not set correctly. As I explained, it can lead to abnormal values, which are often manifested in scale bars. This week, a friend of mine was using GIS to calculate the areas of some […]
