Displaying Your Remote DBMS Data
The process for displaying spatial data from Oracle, SQL Server, or PostGIS is different from the tables we have discussed so far. For more information about accessing remote data, see Getting Started.
Displaying and Importing Data from a Web Map Service
A Web Map Service (WMS) is a technology that gives you a source for data over your Intranet or over the Internet. This innovation is based on a specification from the Open GIS Consortium (OGC) and allows you to use raster map images from servers that also comply with the specification. You must specify the coordinate system within your data request to ensure that the images you retrieve "sync up" or register with your other map data.
This specification supports transparent pixel definition for image formats as well. This allows you to use the images you retrieve as overlays and not solely as the bottom layer of your map.
WMS data may not exist for the geography you are looking for. Further, the data that is provided is determined by the WMS server.