Mapping Hacks

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Chapter 7, Names and Places

#85 Geocode U.S. Locations with the GNIS

HACK

Once we’ve found the place we’re looking for—e.g., Abu Dhabi—we can

look for geospatial information about it:

> SELECT place.name, place.lat,place.lon,feature.name from place, feature

WHERE place.name = 'Abu Dhabi'

AND feature.id = place.feature_type;

We might want a list of all populated places, or all rivers, in a country. This

will be especially useful when we have a list of things and want to figure out

which ones are cities, such as in trying to extract spatial proper nouns from

news items, or extracting spatial references

[Hack #45].

Hacking the Hack

If you have access to a PostGIS database, you can make the gazetteer more

interesting by storing the latitude and longitude as POINT geometry types,

rather than just character strings. With polygons representing country bor-

ders or political administrative areas, you can make much more sophisti-

cated spatial queries; distance between points and “is this place in this area”

are just the start. A further hack that pursues these ideas can be found

online at http://mappinghacks.com/projects/gutenmap/, where the GNS is

used as the basis for a (rough) interactive map of the Peloponnesian War.

See “Build a Spatially Indexed Data Store”

[Hack #87], which covers PostGIS

geometry functions in much more detail.

HACK

#85

Geocode U.S. Locations with the GNIS Hack #85

Make ordinary place ...