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
Last revision 11/1/2011