Thematic Mapping Timeout

The summer and everlasting days are here. I need to prioritize my free time in the upcoming months. All the work reflected on this site has been unpaid - and it won't be continued unless I'm able to earn a salary... 

I wish my readers a great summer (or winter if you're down under)!  

KML projections

I'm waiting for a geobrowser capable of showing KML maps in different projections. The projections commonly used by geobrowsers are not the best choice for thematic world maps. Many cartographers dislike thematic maps rendered on virtual globes, and the Mercator projection is not suited for large area maps. Greenland looks like the same size of South America, while it is actually 8 times smaller.

The coordinate system of KML is geographic (latitude/longitude) coordinates on the World Geodetic System of 1984 (WGS84) datum. Geobrowsers use different projection techniques to render a KML document. Google Earth uses a General Perspective projection, which is similar to the Orthographic projection (see Larry Moores informed speculation of the Google Earth projection). Google Maps and Microsoft's Live Maps both use Mercator projection, which is a good choice for a map that can be panned and zoomed seamlessly. 

My favorite projection for world maps is Winkel Triple, which is the standard projection for maps made by National Geographic. How can I display my KML based thematic maps in a Winkel Triple projection?

Axis maps recently announced indieprojector. This is a web service (based on Adobe Flash) that allows you to (re)project KML files and export the result as SVG. I tried the service with one of my choropleth maps from the Thematic Mapping Engine. 

The above image shows my KML file in Google Maps using the Mercator projection. 

Indieprojector nicely and quickly projects my KML file, but the service is not preserving colour styles.  When will we see a Flash based KML viewer capable of showing KML documents (with styles!) in various projections?  

And what about raster data - is Flash capable of converting image tiles into a seemless Winkel Triple projection?

Introducing Thematic Mapping API

The brand new Thematic Mapping API enables you to create KML based thematic maps from your own data source. This JavaScript library is the missing link between Google Visualization API and Google Earth API (or other geobrowser APIs supporting the KML standard).

A few examples:

• Choropleth map
• Prism map
• Proportional symbol map
• Pie chart map
  

The API is still in beta. Please email me if you would like to try the new API: bjorn[at]thematicmapping.org

Thematic Mapping API will be free to use on non-commercial sites.

Virtual Globes are a good idea for thematic mapping

It's important to seriously discuss and measure the quality of different thematic mapping techniques. I appreciate the critique from Dr. Mark Harrower on the Axis Maps Blog. I encourage everyone to read Mark's blog post - it's an interesting and timely read. This is a quick response to this critique - more blog posts will follow.

In short, I agree with most of the arguments put forward, but I disagree with the conclusions:

1. I agree that my 3-D graduated symbol maps are "pure chart junk", but there are some good examples of 3-D symbol maps. (See previous blog post)
   
   
2. I disagree that 3-D prism maps are chart junk - but thematic world maps on a 3-D globe are problematic. (See previous blog posts: [1], [2], [3]).
   
   
3. I very much disagree that Virtual Globes are a bad idea for thematic mapping, but it's certainly not the only or the ultimate way of showing thematic maps.

I hope more people will engage in this important debate. What is your opinion about 3-D visualisations?

Update 28 April: This issue is currently debated on Axis Maps Blog, Google Earth Design and PTS Blog.  

KML in Research Award to thematicmapping.org

Today, Google announced that one of my KML visualisations won a prize in the KML in Research contest. The animated prism map shows Global Infant Mortality from 1960 to 2005. The statistical data was downloaded from UNdata, a great resource for global statistics. 

The statistics can be explored in time and space. Click here to download the KMZ file.

My dissertation, Using KML for Thematic Mapping, was also awarded the MSc Dissertation Prize at University of Edinburgh. The second part of my dissertation gives a detailed description of the Thematic Mapping Engine, and can be downloaded from thematicmapping.org. 

My Google Tech Talk

My Google Tech Talk "Using KML for Thematic Mapping" is now on YouTube:



Poor video quality, but the slides are also available on Slideshare:



You can try the Thematic Mapping Engine online, and download the source code and documentation. Some funding is required to make a general purpose library for KML based thematic maps. Any ideas?

Merry Christmas and Happy New Year!

I need a vacation from blogging and computers, so I'm going to take one. Have a great Christmas and a Happy New Year! I'll be back in 2009.

(The population prism map is from Edmar Moretti's Brazilian version of the Thematic Mapping Engine. The highest prism is São Paulo, with its metropolitan area ranking seventh among the largest urban areas in the world.)

Michael Jones, Google Earth Chief Technologist, in live webcast at AGU Fall meeting today

The lecture is titled The Spread of Scientific Knowledge from the Royal Society to Google Earth and Beyond and will be given at 6:30 pm San Francisco time. 

Watch AGU webcast

Thematic mapping at Googleplex

After I handed in my MSc thesis in August, Google invited me to San Francisco to present my work. Yesterday, I gave a tech talk at Googleplex about the Thematic Mapping Engine (now open-source) and how KML and Google Earth could be improved to better support popular thematic mapping techniques. My slides are available on SlideShare.

My talk was filmed and will probably appear online. I was a bit nervous during the presentation, so its not my best performance :-&

Anyway, I really enjoyed the discussions with the geo developers, the lunch talks, and the guided tour around Googleplex. Thanks Google!

The next event is the AGU 2008 Fall Meeting starting on Monday. I'm an invited speaker at the Virtual Globes at AGU session on Thursday. 

Thematic Mapping Engine: Source code and technical documentation now available

Many people have asked, - and today, I've released the source code of the Thematic Mapping Engine (TME) under a GPLv3 license. The engine takes statistical data, spatial features and thematic mapping parameters as input and returns a KMZ file. This file can be viewed in Google Earth, or other geobrowsers supporting the KML standard. TME can be accessed from a web interface or a PHP script. 


TME web interface
With the TME web interface, thematic maps can be created in a web browser, without a single line of code. This is achieved through an interactive web form where the user can select between statistical indicators and various thematic mapping techniques. Mapping parameters, like the colour and size, can be readily changed. The form returns a KMZ file which can be visualised directly in the web browser using the new Google Earth plug-in, or downloaded to a computer. 

TME Application Programming Interface (API)
The Thematic Mapping Engine can also be used as an application programming interface (API). This allows thematic maps to be created with a few lines of PHP code. Existing or new applications can use this API to add thematic mapping functionality. This is the code required to create a choropleth map: 

include ('TME_MySQL_DataConnector.php');
include ('TME_Engine.php');

$dataConnector = new DataConnector();
$dataStore = $dataConnector->getDataStore(68, 2005, 0);

$parameters = array( 
'mapType' => 'choropleth',
'indicator' => 68,
'year' => 2005,
'classification' => 'equal');

$map = new ThematicMap($dataStore, $parameters);
$file = $map->getKML();

Requirements
The Thematic Mapping Engine requires the following software (all are open source and available free of charge):

• PHP 5
• MySQL 5+
• Apache HTTP Server 
• Ext JS 2.1
• Google Earth Plug-in

Documentation
This PDF document (7 Mb) gives a detailed description of the Thematic Mapping Engine. The documentation is available under a Creatice Commons Attribution-Share Alike License 3.0.

You should have a basic knowledge of PHP, MySQL and JavaScript before installing the Thematic Mapping Engine.

Download the TME source code on Google Code. 

Enjoy!