Introduction - Open Source Geospatial Tools: Applications in Earth Observation - page 11

Fig. 1.3 QGIS displaying raster and vector data

for displaying data, in particular for high quality map production; for further details
on these packages, the reader is referred to (Neteler and Mitasova 2008).
The aim of this section is to demonstrate how spatial data can be displayed. In
most cases, the following syntax package-name dataset-name can be used
to open the software package and to load a dataset (vector or raster). The software
package can be used tomodify the display options including the zoom settings, colors
and to query the attributes linked to the features.
QGIS has become one of the most widely used GUI-based open source GIS
packages and every release offers more functionality and an increasing number of
useful plugins. One of the advantages of QGIS is that it supports a wide variety of
formats, including the possibility to easily visualize PostGIS and Spatialite tables.
Figure 1.3 shows the QGIS interface; the toolbars provide easy ways to pan and zoom
on the map canvas and the layer tree on the left hand-side displays the layers. The
nine icons to the left of the layer tree, each identified by a ' ' provide a quick way

of adding a format specific layer to the map canvas. By right-clicking on a Layer
and selecting 'Properties' (Fig. 1.4 ) allows the configuration of the view properties.
For instance the symbology of vector layers can be controlled and the options to add
attributes as labels can be defined. It also allows you to choose the specific raster
bands to be visualized.
OpenEV is a visualization toolkit that is developed in Python and is built on
GDAL. It can be used to easily visualize both raster and vector data as well as being
used to develop applications. It was originally developed by Vexcel as a viewer for
the Canadian Geospatial Data Infrastructure and has subsequently been developed
by NASA's Jet Propulsion Laboratory. It is licensed under the GNU Lesser General
Public license.

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