Geography Reference
In-Depth Information
Example projections with their projection properties.
the various projection properties, creates distortions. These distortions can
be minimized by choosing a projection that corresponds as well as possible
to characteristics of the area to be mapped and the known purposes and
uses of the geographic information or map. Inappropriate and erroneous
choice of projections can lead to significant errors and misrepresentations.
Since there are no rules for choosing optimal projections, you simply have
to assess each projection individually and learn through practice and dis-
cussion with other people what projection is best for a particular area, pur-
pose, and use. In many places the projections of most geographic informa-
tion and maps have already been determined. However, different people,
institutions, and countries may use very different projections for the same
area, requiring you to know the distortions that different projections cre-
ate.
4. Geographic information from different projection should not be combined.
Geographic information is particularly prone to errors resulting from the
combination of data from different projections. This also applies to maps,
but since it is very time-consuming to trace two maps and overlay the trac-
ings, in practice you should be most concerned with the consequences of
combining geographic information from different projections, which is per-
haps one of the easiest mistakes to make with GIS. Sometimes, although you
may know the geographic information is for the same place, the combined
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