Image Processing Reference
In-Depth Information
Fig. 6.2 Placement of eight hypothetical sites on the V-I-S model
may be greater than in the rest of the city. Note that sample sites 1-4 represent
segments of a typical urban area, site 5 may represent an industrial area in an arid
region, site 6 may represent a forest or a farm field with a cover crop, site 7 may
represent a desert shrub area, and site 8 may represent a whole village arising in a
desert region.
Regarding classification, sites 1 through 4 could be done at the sub-pixel or per
pixel (dominant cover type) level. Sites 5 through 8 most likely would be approached
at a per-pixel level or groups of pixels in a somewhat homogeneous environment
(see Forster 1985 ).
On a spectral feature space plot the seven sites might appear as in Fig. 6.3 , where
a visible waveband (e.g., red) is placed on the x-axis and near infrared (NIR) is
placed on the y-axis. The commercial core (site 1) with its dominance of impervi-
ous surface lies near the non-vegetation line, dark surfaces to the left and lighter
surfaces grading to the right. High density residential areas (2) lie above the non-
vegetation line, with, in this case, 36% vegetation. Low density residential areas (3)
lie closer to the green point on the plot, where a city park may be nearly completely
vegetated (site 4). Industrial areas (5) may vary considerably along the I-S axis, not
far off the non-vegetation line, with little vegetation, except for so-called industrial
parks which may be similar to residential areas. Here again the virtue of the V-I-S
model appears, exhibiting the variable environmental character of industrial areas,
which land-use maps do not differentiate. A forest or a farm in production (6) rises
close to the green point, perhaps exactly on it, if 100% covered. In a densely forested
Search WWH ::

Custom Search