Geography Reference
In-Depth Information
Example of a TIN data structure. Each triangle is a facet of a hill slope representing
a change in elevation, orientation, or the relationship between these two characteristics.
The transformation concept goes back to Tobler's development and
application of the mathematical transformation concept to cartography. For
Tobler, the map is more than a representation; it is a device for storing infor-
mation. Tobler worked on mathematical techniques and analytical methods
to transform maps into forms of information that can be changed further.
Thanks to Tobler's conceptual work, we regard GI not just as data, but as
data with meaning, which can be transformed and combined with other GI
to create new forms of GI. With the transformation concept comes an
understanding of GI as sets of associations with particular representations
that can be converted to create other sets of associations.
WHAT ARE TRANSFORMATIONS?
Transformations are operations on GI that change the information content
by geometrically manipulating GI and changing it into other GI representa-
tion types. For example, a buffer operation can transform a point that repre-
sents a well into a polygon that represents the zone around the well. This
zone can be represented as positional or field GI, depending on the opera-
tion chosen. The zone can be transformed into the other GI representation
types. Transformations of GI can also change attributes. An example of an
attribute change is converting temperature recorded in degrees Celsius to
degrees Fahrenheit. In both cases, the key change involves transforming the
GI representation. What information is measured for a point, such as a well,
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