The location of objects in space describes both, its position in space as well as its relation to other objects. The
location includes two concepts: The position and the neighborhood.
In everyday life, the notion of neighborhood is often used to locate objects; for example, one would say that the
grocery store is located next to the church. In this example, location involves the concept of neighborhood, the measuring
of proximity in relation to a reference object whose position is perceived implicitly. Obviously, such a location does
not fit to the
description of a set of complex objects such as those described in GIS. In GIS the requirements are even higher as they
were for
conventional mapping. In this case, one talks about the positioning of objects on the terrestrial surface. The establishment
of a
reference system and the definition of a metric space to measure distances are necessary. The simplest and most frequently
used system
is the Euclidean metric. The space is assumed to be flat; the metric space is assumed to be constant, defined by a perpendicular
axis
system. The mapping systems based on this principle are adopted by GIS.
In addition you can consult the book
Datums and Map Projections for remote sensing, GIS and surveying
(Jonathan Iliffe 2000).