The Geospatial Search Engine (GSE) is a web application that provides a search engine for Geographic Information System (GIS) map servers and layers. GSE supports web map services (WMS), ArcGIS services, ArcIMS services, and shapefiles for download. The application is hosted in the Amazon Web Services cloud and is available at http://wildfireapps.org/GSE/GSE.aspx.
This system combines a searchable database of GIS map servers and layers, with a web crawler for both locating new data and updating existing data. GSE is currently a standalone application, but there are plans to build a user friendly API to allow further access to the search engine.
The GSE user interface is built using open source components such as Ext JS, GeoExt, and OpenLayers. The Google Web Search API is integrated to obtain web search results based on user specified terms. The user interface consists of the following parts.
Search Panel - The left side of the interface is used for specifying search terms and retrieving a list of map servers and layers. For shapefiles, a web page link is provided so that the user may review the web page containing shapefiles available to download. The GSE database is searched using the specified terms, and results are returned to the user in a tree view. There is a separate node in the tree view for each of the 4 server types (WMS, ArcGIS Server, ArcIMS, and Shapefile). Below the server type node is a node for each map server, and each map server has nodes for each layer that meets the search criteria. It is possible to have a map server node with no layer sub nodes. This occurs when the map server abstract or keywords contain the search terms but none of the layer abstracts or keywords contain the terms. As the user selects nodes in the tree view, the total number of layers and the number of layers that meet the search criteria are displayed in the lower right corner of the search panel.
View - The View button below the search panel will either display a preview map of the selected layer, or if a shapefile server is selected, open the web page.
Get All Layers - The Get All Layers button will retrieve a list of all layers for the selected map server, rather than just the layers that meet the search criteria. The layers will be listed in the layer list panel on the right side of the application interface.
Layer List Panel - The right side of the interface allows the user to specify a known URL and retrieve available map layers. When a URL is specified that is not found in the database, the GSE application will contact the map server to retrieve metadata and add this server to the database. This allows for a convenient method of manually adding map servers to the database. The list of layers is returned to the user and displayed in a table with Title and Description columns. By clicking on the column headers you can sort the layers by Title or Description.
Preview - The Preview button at the bottom of the layer list panel displays a preview map for the selected layer. This map contains a background map for reference purposes in addition to a map of the selected layer. On the right side of the map is a plus symbol. Clicking this symbol opens a small window allowing the user to turn layers on and off. On the left side of the map is a navigation bar, allowing the user to pan and zoom the map. Panning can also be accomplished by clicking and dragging the mouse. Holding the shift key down while clicking and dragging on the map will draw a rectangle defining an area to zoom to. The mouse wheel can also be used for zooming in and out. The user can also double-click a layer in the list to display the preview map. Note that the GSE application currently only displays preview maps for layers that support the following spatial reference systems:
EPSG 4326 (latitude/longitude based on the WGS84 datum)