Wednesday, May 25, 2011

Choropleth mapping techniques for Web2.0

For my recent project, I have to display county wise time series data of disease pattern in web map for the conterminous United States for 20 years. In addition, I have to use Google maps as base layer and should overlay images on the top of it.  The concept sounds easy, and it was also similar with choropleth or thematic mapping. However, it should be in the Web 2.0.

I tried to figure out what are the possible ways to achieve this, I tried and few of them. Here I am going to share the pros and cons of these methods in a real quick and dirty style.

Choropleth with GFT
1) Google Fusion Tables

Easy, No understanding of computer programming needed. Upload small or large data sets from spreadsheets or CSV files. Visualize your data on maps, timelines and charts. Pick who can access your data; hide parts of your data if needed. Merge data from multiple tables.

Not much flexible and you can’t tweaks easily according to your needs. 

Choropleth with Cartographer.JS and Google API
2) Cartographer.js and Google API

Pros: It generates choropleth maps directly from database or other standard data handlers. Fast for small area mapping.

Understanding of JavaScript is needed. It supports only US (County and State level data). I got performance is worst if we map entire 50 states. I recommend it to use to map few states only. Although cartographer.js's documentation claims browser friendly, it is horrible with IE, works so so with Firefox and chrome. 

Choropleth with Polymaps
3) Polymaps

Pros: Polymaps is a free JavaScript library for making dynamic, interactive maps in modern web browsers. Simple. You can find cool demos here.

Programming Knowledge is necessary. 

Choropleth with Geoserver and Openlayers
4) Mapserver or Geoserver & Openlayers Map

Finally, I use Geoserver & Openlayes Map for my project.

Pros: More control over maps, projections, and Legend, supports tiles cache, not limited to US Shape only, supports Google/Bing/OSM/Yahoo maps as a background layer as well as can switch among layers. Based upon Javascript/JSON and AJAX. Browser friendly.

Cons: Knowledge of Javascript/JSON, WMS, and WFS required. Cross domain AJAX problem will be occurred if Geoserver and Apache server are running from different locations or different port.

Fusion tables , Geoserver , GIS , Google , Map , Openlayers , PolyMaps


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