Mapping Hacks

Map Imaginary Places #100

Chapter 9, Mapping with Other People

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HACK

rather than separate database columns for latitude and longitude. Here’s

how you go about adding a geometry column to a Postgres database with

PostGIS installed:

SELECT AddGeometryColumn ('database_name','table_name','column_name',<SRID>

,'GEOMETRY',2);

This statement adds a GEOMETRY field (which can contain points, lines, or

shapes) to a table of our choosing. The fourth item in this statement, the

SRID, is replaced with our new ellipsoid identifier, 9999, as approved by the

Intergalactic Astronavigation Consortium. The last item is dimensionality,

indicating that this piece of geometry has two dimensions. The latest release

of PostGIS supports four-dimensional geometry, which is, frankly, worri-

some.

“Build a Spatially Indexed Data Store”

[Hack #87] provides more detail on how

to create and query spatial tables in your database. To get started, add new

columns describing points into your PostGIS database as shown here, where

the last value is the SRID of your imaginary reference system:

INSERT INTO table_name (column_name) VALUES

(GeometryFromText('POINT("<latitude> <longitude>")',9999))

Now each city, town, and other landmark in your imaginary world can have

geometry that can be queried associated with it. Cities might be scattered

round an equatorial strip of land near latitude 0, or huddle near the cold

poles on a terraformed ...