Introduction - Open Source Geospatial Tools: Applications in Earth Observation - page 10

Another feature of the software packages used in this topic is that they are available
under the main operating systems currently used: Microsoft Windows, Mac OS and
Unix/Linux distributions. The main objective of the topic is to clearly explain how
the core utilities of GDAL/OGR can be used for powerful geo-processing.
Our examples will be cross-platform, however, invariably we show the power
of the shell environment for combining tools together to develop more complete
processing tool chains that can be managed in an operational, batch environment.
For instance, we will use GNU command line tools, like grep , awk and sed as build-
ing blocks. On this point, it is important to note that we will rely more heavily on
*nix/BSD based distributions. Nonetheless, MS Windows users can implement and
attain the same functionality using Unix-like emulators (e.g. Cygwin), MS-Windows
ports of the GNU command line tool packages and using Virtual Machine environ-
ments running Linux. In addition, the GDAL/OGR tools can also be accessed from
QGIS through the GDAL plugin. We also demonstrate the use of GDAL/OGRPython
bindings as a potentially more flexible solution for readers using MS Windows.
For readers of this topic that are not adept in Linux distributions, we recommend
that the OSGeo Live DVD or the Virtual Machine (VM) be used as a learning tool to
accompany this topic. Further details are provided in Appendix B.1 relating to the
installation and configuration of the VM relevant to this topic. The advantage of this
approach is that a fully fledged Linux system can be run within an MS-Windows
environment without the need to change the core installation of the underlying com-
puter. Furthermore, the OSGeo Live DVD includes all of the pre-compiled geospatial
software packages endorsed by OSGeo, as well as the myriad of command line util-
ities. In addition, we have included all of the datasources and additional software
packages covered in this topic. Appendix B.1 provides a brief step-by-step guide to
set-up and download the Virtual Machine on an MS-Windows operating system.
For readers already using a Unix/BSD based distribution, we provide brief infor-
mation on installing the required packages using the software repositories or the pre-
compiled software packages (e.g. deb or rpms). Although compiling and installing
packages using the source code is recommended for a highly optimized and flexible
operating system, it is not recommended for the faint hearted nor a new user of the
command line.
1.5.1 Geospatial Visualization Tools
Although the focus of this topic is on geospatial analysis, we feel that it is necessary
to briefly introduce some software tools that can be used to visualize both vector and
raster spatial data. There is a plethora of open source packages available that can be
used and we will introduce some of the principal packages that are widely used. They
include QGIS, OpenEV and the Orfeo Toolbox viewer. These examples are perhaps
the most straightforward to use to quickly display your geospatial data, but clearly
other packages provide more options and flexibility in how the data are rendered.
For instance, GRASS GIS and R Statistics provide more sophisticated approaches