8. How do we represent geographical information in a computer?
Location can be described using
a number of methods including map grid references, postcodes and place
names. A GIS can find location based
on any of these. The
Environment
Agency website is a good example allowing you to search for information
about your local area by any of these methods.
The shape of features can be represented using points lines and polygons (vector)
and grids (raster). Multimap is able to integrate both forms of representation
together. By overlaying the map (made up of points, lines and polygons) on
the aerial photograph (a raster) it is possible to see how a GIS can represent
the
same features in two different ways.
Tables of geographic information are used to describe many features (known
as attributes). The Census website is able to access these tables and display
records
from them so that descriptions are displayed when your mouse pointer is placed
over the map.