Geography Reference
In-Depth Information
PRINCIPLES OF GI AND CARTOGRAPHY
Surveying, GPS, Digitization
Chapter 7
Surveying, GPS, Digitization
Collecting and communicating reliable geographic information about things
and events requires knowing in a systematic fashion where they occur. Pro-
jections, location systems, and coordinate systems provide key geographic
reference frameworks for systematically locating observations and measure-
ments of distinct locations. Geographic representation and cartographic rep-
resentation rely on the collected location information to make accurate and
reliable GI. With various techniques of recording location, surveying, GPS,
and digitalization are three generic ways of recording the locations and char-
acteristics of things and events by directly observing them or indirectly mea-
suring their location. In all three forms of location measurement, the
collection of positional information requires the systematic collection of
measurements.
Geography distinguishes between position and place, though the terms
in many other usages are often synonymous. “Position” refers to the system-
atic measurement of the place associated with a thing or event. “Place” only
refers generically to the site, usually referring to something more familiar.
For example, the place where the Eiffel Tower is located is Paris, France. The
position of the Eiffel Tower is approximately East 2.37 longitude and North
48.7 latitude. We should also note that we use the word “approximate” when
referring to position unless we have accurate measurements of location in a
geographic reference framework
Considerations of geographic representation and cartographic repre-
sentation issues have strong impacts on the methods and techniques used
for collecting positional and attribute data. How we wish to show something
by itself and in relationship to other things and events involves defining a
number of characteristics which in turn specify how the position of objects is
determined. For instance, the location of a forest may be known reliably, but
the location of the trees in the forest is another matter. If we need to know
the location of the trees we have to decide what a tree is (to avoid including
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