Digital Geography

The Spiegel Magazine and their “maps”

Today I stumbled upon a “map” on Spiegel Online ( an import news page in Germany ) which shows the spied countries of the NSA. As we already know leaflet quite good and also tried other mapping possibilities I was interested in what they are using for this map which is more informative than this useless map. So looking on the source code: It’s a library called jvectormap.

Online GeoJSON Editor

The web is built upon a small set of languages that are present everywhere. Besides HTML, Javascript is the most common technology around here.  So it is not a surprise that web cartography adapts this technology and uses the native javascript object type to store its vector data. The specification is called GeoJSON (for Javascript Object Notation) and extends the JSON model with geometry fields. But if you ever needed to write some lines of Javascript, you’ll know that it’s brackets can drive you crazy. So why would someone want to write table-like structures in such a quirky format? The…

how to create clustered points in leaflet

The leaflet API is very simple and tries to deliver best performance and style for commonly used features like tilelayers, points and lines and markers in general. So when we would like to visualize points it is possible to have a very large numbers of points. So lets have a look on such an basic example. I’ve created a point shape file with QGIS which has approx. 1.000 points embedded. Let’s have a look on a normal webmap with this density of information: As you can see, we’ve inlcuded a second js file with the point information called points_rand.js. You…

Make it simple – How to add Line Simplifcation to your Web Mapping

When Mike Bostock published his (re-) implementation and demonstration of Visvalingams algorithm for line simplification he attracted considerable attention on that. What is a little bit strange in my opinion. This algorithm is old hat as like the second more well-known algorithm invented by Douglas-Peucker. Both can be seen as the basic concepts for the simplification of linear geometric objects when a quick & easy implementable point reduction is essential. And this is what they can achieve…reducing the amount of points, by analysing the topology of each point…not more but also not less! They are well-known and (relativ) easy implementable…

D3-Basics – All you need is a selection!

Since a while I am programming with the JavaScript library D3.js … and … I am addicted to it! As I would like to present some tutorials on D3’s fantastic possibilities to create and design webmapping solutions … I think it would be good to give you a description on the things that I would identify as elementary. Caution! This tutorial could be a little bit too detailled for you, when you are a skilled JavaScript programmer! I am sorry for that! But when you are a noob in JavaScript, as I was when I began to program with D3,…

a minimal web-map using OpenLayers (part 1)

Web-mapping is used everywhere since GoogleMaps and GoogleEarth revolutionized our topographical and geographical perception. Keeping that in mind it is useful to get some insights in web-mapping possibilities. An easy-to-use open source application for that is a javascript library called OpenLayers. You can run this on your local Windows or Linux machine easily: Download it from the OpenLayers website or if you are using Ubuntu as your Linux distribution just search for “openlayers” in the Software-Center or use your terminal: But for a real minimal example you will only need 2 files in a folder: the openlayers.js and a index.html…