16 Computing in Geographic Information Systems
The core computing modules that make GIS are geodesic modelling which
models planet Earth, sea and space to an approximate geometry. The outcome
of this modelling is a mathematically defined surface or modelled surface. All
the spatial objects are located, measured and referenced with respect to the
modelled surface. The next set of computing involved in GIS is imparting
a suitable ‘frame of reference’ or ‘coordinate system’ to the datum surface.
There are different types of coordinate systems designed and being used in
different datum surfaces and different applications. In GIS often there is a need
to transform spatial data captured using one datum and coordinate system to
another datum or coordinate system ...