Raster Data Explained - Open Source Geospatial Tools: Applications in Earth Observation - page 55

filename
The name of a file containing WKT, PROJ.4 strings, or XML/GML coordinate
system definitions can be provided.

3.2 Single and Multi-band Images

For single band raster images there is only one value assigned to each pixel. The
values can represent two distinct types of data: continuous fields (e.g. represented as
floating points) and categorical maps with a discrete number of classes (e.g. a land
cover map). The greyscale image in Fig. 3.3 a is an example of a continuous field that
represents a digital elevation model (heights). The binary mask (0 or 1) in Fig. 3.3 b
and the land cover map in Fig. 3.3 c are examples of categorical maps.
The distinction of continuous fields and categorical maps is important when deal-
ing with methods that involve resampling techniques (see Sect. 8.2 ) . Continuous
fields can be interpolated to meaningful values. For categorical maps, however, inter-
polation can lead to meaningless values that fall between two categories.

(a) (b) (c)

Fig. 3.3 Examples of single band raster images, a greyscale image, b binary mask, c landcover
map with three classes

Fig. 3.4 Example of multi-band image