Investigation into the Applicability of Flex 3 Technology to Support Mapping and Spatial Data Visualization on Web Pages, 10-R8029

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Principal Investigator
Stephen R. Johns

Inclusive Dates:  01/05/09 – 05/05/09

Background - A variety of technologies is currently being used to present spatial data to the general public. Companies like Microsoft and Google have produced web-based mapping tools that allow organizations to quickly and easily display spatial data. These mapping technologies rely on transferring the map data from public servers, and this means that a map may be unavailable because of issues with the map server or with the network connection to the map servers. The purpose of this project was to determine if a map based on Flex 3 technology was a viable alternative for supporting web-based mapping and spatial data display. To be considered a viable alternative, the Flex 3 map would have to perform basic navigation functions (i.e. pan and zoom), load base-map data files, render and manage multiple data layers, and meet the performance requirements for loading and rendering map and spatial data.

Approach - The investigation into methods for implementing a map using Flex 3 focused on two areas. The first area of investigation was to identify and evaluate the specific features within Flex 3 that could be used to support geographic map rendering. Features investigated included bitmap and vector data rendering, text label rendering, user input processing, pan and zoom operations, and clipping of data that exceeds the current map view. Finally, performance was compared to other web-based technologies. The second area of investigation involved identifying sources of geographical data that could be used to build maps.

Accomplishments - A map prototype based on Flex 3 technology was developed that successfully demonstrated the map objectives. Maps were created using combinations of bitmap image data, Scalable Vector Graphics (SVG) data, and other types of spatial data. Updating the map quickly during pan and zoom operations required an in-depth study of how the Flex 3 user interface components were implemented and organized. A variety of Flex 3 components were evaluated and prototyped before a combination of components and techniques was found that provided an acceptable level of performance. Mechanisms to render and independently update layers of spatial data on the map were developed. These mechanisms were capable of keeping the map current with data update rates of one-second intervals. Two different mechanisms to render text labels were developed. A variety of geographical and spatial data sources was identified. The overall performance of the map was compared against similar implementations using Google Maps and Microsoft Virtual Earth maps. Performance of the Flex 3 map prototype compares very favorably, and in many cases exceeds, both Microsoft Virtual Earth and Google Maps.

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