GIS and the Internet

GIS can use the Internet for a variety of things:

• Data download portal, such as the USGS Seamless Server.  In this model, you go a web page, select data, download it it your computer, and then use it locally.  This is just a faster and more convenient way to get data than the old alternatives of CD-ROM or similar hardware solutions.
• Live feeding of data, much as Google Earth or Google Maps do.  If you lose the internet connection, you lose the maps.  The GIS program decides you want data for a map area, and requests it from a web server.  For this operation the web server has two choices, which determine whether the server has to do more processing or store more data:
  • Serve the data in tiles.  You request a tile, of a specific area at a specific scale, and the server just finds the file and returns it to you.  It will probably have a pyramid of coverage, with several scales available.  Larger scales have smaller tiles, with much larger downloads to cover the same area.
  • Serve the data exactly as requested, by scale and coverage area.  This requires the server to run a program to get the data, merge or subset as required, and then send you the file you want.
• Live creation of maps on the web, in a browser, where you can download a final map.  This will probably not be a good choice for further GIS analysis, but can be very useful for casual users.
• Services like Address Geocoding, converting between street address and geographic coordinates.

Last revision 11/1/2011