Geography Reference
In-Depth Information
Another impact of using MBRs to compare features takes place when
doing a selection in our favorite desktop GIS application. Suppose we
cally choose the
Select
tool and either point at or draw a small rectangle
inside P2 to select it. You can guess what will happen if MBRs are used
to determine what should be selected. Since our selection rectangle
may fall within the MBR of both P1 and P2, we could end up with both
selected (and usually highlighted). This isn't really desirable and can
often be confusing. Although MySQL provides storage and MBR func-
tions, it isn't really suited for applications that depend on the correct
functioning of spatial functions for selecting and identifying features.
To be fair, the MySQL developers freely admit the nature of their imple-
mentation and also imply that they may support the OGC specification
fully in future releases. Support for MySQL spatial data is already avail-
able in OGR and will likely show up in other OSGIS applications soon.
7.3
Getting Started with PostGIS
In this section, we'll look at how to enable PostGIS in your PostgreSQL
database and load some data from shapefiles and perhaps from other
sources. We assume you already have a working PostgreSQL install. If
not, refer to the installation section of the manual
5
where you will find
detailed instructions for getting PostgreSQL up and running on your
platform. If you're lucky, PostgreSQL is already installed, and you are
ready to proceed with getting PostGIS set up.
Getting PostGIS can be easy if you are running the right platform. You
may find a binary version available for download.
6
Otherwise, you will
have to build from source. If you are running Linux, be sure to check
for a PostGIS binary using your package management tool. Many distri-
butions include PostgreSQL and PostGIS, making it easy to get started.
If you are running Windows, the latest PostgreSQL installers include
an option to install PostGIS. It's not selected by default, so make sure
to you include it when choosing options during the install. Once you
have the software in place, you're ready to set up a database and add
the PostGIS extension and tables.
5.
6.
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