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This short article describes the architecture of the EcoMap Costa Rica map pages as an example of a typical geospatial web application that uses multiple software technologies. It is the first of two articles. The second article uses examples from the EcoMap Costa Rica website demonstrating the use of OpenLayers in order to combine Virtual Earth with other map technologies.
During development of the EcoMap Costa Rica project and website, it quickly became apparent that both Google Maps and Virtual Earth simply did not have the required detail in the study area. Therefore we had to create our own maps. MapServer was chosen as our main map serving engine. MapServer serves the Outline map, ASTER Satellite image, and Synthetic Stream data to the browser as a series of map tiles. The map webpages use OpenLayers to control the map. This is an open source Javascript client that can receive online maps from a variety of sources. OpenLayers receives the map tiles from MapServer using WMS and also implements a cache for faster response times. As well as the WMS layers, OpenLayers reads three layers (Icons, Map Survey, and Map Survey) from static KML Files delivered by HTTP. These KML files were created from field data using a combination of file conversion utilities and text editors. Finally, the grid layer is 'manually' drawn using Javascript. A second version of the map uses a Microsoft Virtual Earth base map instead of the MapServer Outline base map. OpenLayers is very flexible and can easily incorporate a Virtual Earth layer. Virtual Earth adds better coverage of wider Costa Rica, but lacks detail in the study area. This architecture is illustrated in the following diagram: 
The Outline Map layer shows country and administrative boundaries. These are shapefiles that are available from the US Centers for Disease Control as a part of their Epi Info™ system. The ASTER Satellite Image layer is a near infra-red daytime image taken by the ASTER imaging instrument flying on the NASA EOS Terra satellite. The image that we have used is taken from the ASTA Volcano Archive AVA) for Arenal. These images are available via Smithsonian's Global Volcanism pages for Arenal. It was acquired on 29th August 2005, and has a Granule ID of SC:AST_L1A.003:2030725270. The Synthetic Stream layer plots rivers, creeks, and streams that have been derived from DEM (digital elevation model) data. Ie. these are theoretical river positions based on height data. This works well for hilly areas, but it is poor for flat and low gradients areas. The data was calculated by the Inter-American Biodiversity Information Network (IABIN).
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