Case Study on Vector Spatial Analysis - Open Source Geospatial Tools: Applications in Earth Observation - page 279

Fig. 16.5 Google Earth digitize polygon
type, i.e. if you are digitizing water features (lakes, rivers, etc.), you should enter a
related name (e.g. water1, water_lake, etc.). The reason for this will become clear
subsequently when we add additional attributes. Once the digitizing is complete,
we double click to close the polygon at which point Google Earth will display the
polygon with a shaded colour.
One of the drawbacks of Google Earth is that each of the individual land use types
needs to be digitized separately, i.e. the above data creation step needs to be repeated
for all of the 15 land-use features that are required for the classification.
Once all of the features have been createdwithin the folder VectorCaseStudy ,
we can export them as a KMZ file, which is a compressed XML format that is used
by Google Earth. As it is fundamentally XML, we can first unzip it and then open the
file in a text editor and view its contents (a subset is presented below), that includes
the name of the polygon and the individual coordinates of the polygon's vertices.
We will now preprocess this file using OGR to prepare it for input into the image
classification.