Functions of GIS
Functions of GIS include:
1- data entry
Data acquisition is often the most expensive and time consuming part of any GIS project , It may require:
• Purchasing data from commercial vendors
• Acquisition of data through field collection
– Aerial photography
– Satellite imagery
– GPS
– Manual digitizing
• Download from government or other sources
The advantages of digital versus analogue data are outlined in the table below:
GIS Data Sources
• A practical question: Where does one get GIS data?
- Construct GIS data from GPS measurements and attributes for particular locations.
- Transfer existing spatial locations and non-spatial attributes into a GIS.
- Digitize data from existing paper maps, photographs or imagery (either in vector or raster format).
- Obtain through data providers.
• Many existing GIS data sets are freely available.
• The Internet is widely used to distribute GIS data:
– Local, state, federal government agencies.
– Universities and research institutions.
– Private sector data providers.
• It is critical to have the following issues in mind when downloading data:
– Metadata including formats, resolution and projections.
– Data sources (remote sensing, census, GPS, etc).
– Data cost (if any).