This article was previously published at GeoChalkboard in the form of a two-part article, and has been reproduced here with permission.

User expectations for web mapping applications have changed dramatically in the past few years thanks largely to Google Maps and Microsoft Bing Maps (nee Virtual Earth) technologies which brought “Web 2.0” to the masses and forever changed our expectations of how these applications should look, perform, and access data. With the advent of “Web 2.0” your applications must meet certain expectations including sleek interface controls, a better user experience driven largely by asynchronous data processing and client-side scripting, drag and drop capabilities, and the ability to combine or “mashup” multiple data sources into a single application. A number of JavaScript toolkits including Dojo, jQuery, Yui, Mochikit, and many others have been developed to enable these capabilities. ESRI recently released the JavaScript API for ArcGIS Server which was built on top of the Dojo toolkit and enables developers to take advantage of the capabilities provided by this JavaScript toolkit. Dojo is also a highly flexible toolkit that allows you to pick and choose the pieces of the toolkit that best fit your needs. According to Jayant Sai of ESRI, “We like the fact that our users can use the whole Dojo toolkit to build their next generation web 2.0 mapping application, or use just our mapping components, without really getting into the hardcore JavaScript pieces of the toolkit.”

This article concentrates on the use of Dojo for building web mapping applications. We will not only examine how Dojo is used with the ArcGIS Server JavaScript API, but you’ll also see how you can use this toolkit with other mapping API’s including Google Maps. We will start with a simple overview of Dojo and how it can be used in your web based GIS applications.

This is the second part of an article written by Chris Duncan. The first part of the article introduced Plug & Play Maps and was published on Monday.

This is the fun part – bringing your data to life by displaying it in a visually engaging way that immediately and intuitively conveys to your visitors what you want them to understand about the data. There are two general aspects of data display you can control: what type of symbol to use when displaying the data (icons, charts, lines, or polygons), and how to vary those symbols to reflect your data values (no variation, varying color, or varying weight).

The WMS standard is a popular choice for delivering map tiles from a web server. When combined with a modern AJAX client (eg. OpenLayers) it can produce a compelling geoweb application, but the download performance of WMS tiles can sometimes be inadequate. The easiest way to improve the WMS tile rendering performance for the end user, is to implement a tile cache.

Here we look at two WMS tile cache applications: TileCache and GeoWebCache.