Geoscience Reference
In-Depth Information
use integrated with proprietary software. Its incubation procedure for projects includes legal verifi-
cation steps to check that code is properly copyrighted and licensed and that the conditions of use
are clear. Many of the geospatial library projects offer code under X/MIT, LGPL or other licences
permitting the distribution of linked builds of closed-source downstream components containing
modified upstream components.
McIhagga (2008) discusses some of the ways in which communities of practice have developed,
with particular reference to web mapping and, in his description, the open-source web mapping
“ecology”. Chen and Xie (2008) show how open-source SQL databases with spatial extensions fit
into the bigger picture; this is very evident also from Figure 14.1. There is also a good deal of excite-
ment around the use of non-relational databases with spatial data, such as GeoCouch* extending
CouchDB; others were also presented at the OSGeo meeting in 2011.
The PostGIS spatial extensions to PostgreSQL are widely used; PostGIS is licensed under the
GNU General Public License (GPL), while PostgreSQL itself is licensed under its own licence,
which is similar to the MIT licence. Software licensed under GPL is termed Free Software, because
licensees are required to make available modified source code if they also publish binary versions of
the software for sale or otherwise. Software with more “liberal” licences does not oblige licensees to
contribute back to the community if they publish binary software, although many do anyway. The
term Open Source software includes free software as a strict subset, that is, all free software is open
source, but not all open source is free in the understanding of the GPL.
The following review does not attempt to be exhaustive, but rather to establish a basis for the next
section, in which links with
R
will be presented.
14.3.1 g
eoSPatial
l
iBrarieS
Geospatial libraries are important in applying GC because they encapsulate knowledge about the
computational processes involved in handling spatial data. Once the underlying regularities and
structures have been established, and the library created, other software components may use it
to provide functionality that they need without having to reimplement. Naturally, more than one
library may exist for each niche, and the boundaries between libraries may overlap, but they do offer
opportunities to benefit from modularisation.
One of the central geospatial libraries closely associated with GC in its development motivation
i is G e oTo ol is
†
Turton (2008) describes its progress from beginnings in a doctoral research proj-
ect in Leeds up to about 4 years ago, and its position as a major upstream component for both
desktop applications and web mapping applications written in Java is, if anything, even stronger
now. It builds on other components, such as the JTS Topology Suite,
‡
but implements its own code
for spatial reference systems (SRSs) in Java based on the International Association of Oil & Gas
Producers Geomatics Committee, formerly known as the European Petroleum Survey Group (OGP
ESPG
§
) database. The
R
cshapes
package (Weidmann et al. 2011) bundles JTS run through
rJava
for polygon boundary line generalisation and distance calculation but is probably the only
R
geospa-
tial package using open-source geospatial Java components (Weidmann and Gleditsch 2010). The
Geospatial Data Abstraction Library (GDAL, pronounced GooDAL, with stress on the oo, because
it was intended to be object-oriented)
¶
is a crucial part of the upstream geospatial library infrastruc-
ture. Downstream components needing to read raster data can instead read from the abstracted
object representation, rather than being obliged to implement interfaces to each format separately.
As Walter et al. (2002) describe its beginnings in relation to the OpenEV desktop application, it
simplified reading and writing raster data.
*
https://github.com/couchbase/geocouch/.
†
http://www.geotools.org.
‡
http://www.vividsolutions.com/jts.
§
http://www.epsg.org/.
¶
http://www.gdal.org.
