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Q19: How did you calculate the latitude and longitude for my town since your
information puts it at a point that is actually outside of town?
The lat/long for each place was a calculated with reference to the legal
boundaries of the entity as of the 1990 census and 2000 census respectively,
not to the center of a collection of buildings (like the central business district).
The calculations were done at that time on a computer using the boundary
lat/longs, not by sending people out to each place with a GPS receiver. The
resulting point is the approximate geographic center of the polygon making up
the legal entity. Whether that is actually useful to anyone is an individual
matter. The reason we created these files (they exist for several levels of
geography) was for various data analysis and thematic map presentation
applications. They provided us a convenient way to link the statistical data
being reported for these entities to a geographic coordinate location. They
are useful at larger scales of analysis or presentation, for example at the
state/national level for place or county coordinates. We put these 1990 census
and census 2000 Gazetteer files on site for downloading because people have asked
for copies.
Note that the legal boundaries and their relationship to the built-up area of
a place are local responsibilities. We get the boundary information directly
from the local governments.
As for the precision of the lat/long coordinates, we recognize that the
accuracy of the coordinates is not as good as the precision implies. The
extra precision is useful to us for our processing operations by giving us a
mathematical way of separating and keeping in order closely spaced features
(roads, boundaries, etc.).
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