Showing posts with label boundaries. Show all posts
Showing posts with label boundaries. Show all posts

Wednesday, 28 August 2013

Natural Earth for GIS data

People often ask me where they can get GIS data to use for projects, analysis and general mapping. In the UK we now have OS OpenData, which is very nice and very detailed. There's also a new GIS portal from the Office for National Statistics - built using the Geoportal Server. Other GIS datasets are available, from organisations like Natural England, but in this post I thought I'd highlight the excellent - and totally free - Natural Earth site which is very well known in the geodata community but perhaps not more widely. It really is absolutely fantastic.


A little bit of technical information....

  • Natural Earth Vector comes in ESRI shapefile format, the de facto standard for vector geodata. Character encoding is Windows-1252.
  • Natural Earth Raster comes in TIFF format with a TFW world file.
  • All Natural Earth data use the Geographic coordinate system (projection), WGS84 datum +proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs
Whether you're looking for data to make a general world map or a more detailed local area map you will find what you are looking for here. It's not as detailed as OS data for Great Britain but then many GIS users don't need that level of accuracy. Another screenshot below showing the various download options...


Finally, taking my inspiration from the worst website in the world, and Ken Field's blog - I've made an absolutely awful map using some of this data*. Can anyone do a worse one?


*I actually did this as part of my work in developing some new GIS modules. I tried to pack in as much bad practice as possible just as an extreme example of what not to do.





Friday, 19 December 2008

Simple is often better

When working with GIS boundaries, I'm often only really interested in them from a general point of view so that I can create simple choropleth maps. Also, if I'm trying to publish them over the web, there's no need to provide very accurate boundaries. Therefore, it's always useful to have different ways of simplifying boundaries. I have used various tools for this, including ET GeoWizards free tools and some of the in-built functionality of ArcGIS 9.x. However, the most convenient and flexible tool I've come across so far is MapShaper. They have an alpha testing version of their Flash-based interface here and it's really easy to use. There is a 16MB file size limit, but I've still found it to be very effective. It doesn't require much (if any) expert knowledge of GIS or of file formats, and you can simplify or smooth using a number of different methods (see images below). All in all, a very useful tool!