Water and land
With the increase of bands, the spectral reflectance value of water body decrease, i.e.
b
ij1>b
ij2>b
ij3>b
ij4>b
ij
5>b
ij7.Meanwhile, band 5,7 can be used to select threshold to segment
water. But due to the special effection of bedload in YRD, CH3, CH4 >CH2. So, we first using
water spectral feature model to extract water, then within the region of water body, classification
is conducted to obtain different depth classification map (shown as figure 3). It simply and
distinctly reflects the water region distribution of YRD.
Figure 3 Water classification map
Vegetation and non-vegetation
Vegetation has high reflectance value in band 4.and in band 3 there is low reflectance. For
this character, b
ijv=b
ij4/b
ij3 is often taken as the index to identify vegetation region and non-vegetation
region. Certainly, there is much other vegetation indexes. When it is used in image
segmentation, we define the following rules:
bijv>a1; vegetation region
Pixel(i,j) bijv <=a2; non-vegetation region
Between them.confused region
Figure 4 Based on spectral model segmentation of vegetation and non-vegetation
Sandy land and general land
For non-vegetation region, we can farther separate it into bare soil, build-up soil, residence etc.
But for coastal region, sandy soil is leading object. Because spectral value of sand is lower than
other kinds of non-vegetation, especially band 7 (including water). According to the rule, we
can extract sandy soil in the non-vegetation region (shown as figure 5).
Figure 5 Based on spectral model
segmentation of sandy soil
