443
O -\ 1 1 1 1 1 1 i 1 1 | r—1 I |
O 10 20 30 40 50 60 70
TM band 3
Figure 3. Feature space plot of TM band 4 Figure 6. Greenness plotted against WDVI
against band 3.
1 = water
2 = town
3 = light soil
4 = darker soil (mixed)
5 = vegetation
6 = dense vegetation
The resulting image for this WDVI sat is given
in Fig. 4.
(5) Calculation of Greenness
The Greenness for TM data (after offset
correction) may be calculated by using the
coefficients given by Crist & Cicone (1984)
in a global (not site-specific) way. These
coefficients are provided in Table 3.
In Fig. 5 the image of the Greenness is
given. Comparison of Figs. 4 and 5 confirmes
the statement in section 2.2 that the WDVI
and the Greenness are much alike. In Fig. 6
the Greenness is plotted against the WDVI sat
for the training set. The deviance from a
straight line is small (r = 0.997).
5. CONCLUSIONS
The WDVI can be applied to satellite data,
yielding results comparable to the Greenness
of Kauth & Thomas (1976). As a result, for
many applications not all TM bands are
needed, but only bands 3 and 4 may yield the
information needed. This induces a
considerable simplification of data analysis.
Subsequently, a straightforward estimation of
crop characteristics, such as LAI, is
possible.
Like the Greenness, the WDVI does not correct
for atmospheric influence in a multitemporal
analysis. Some other procedure for
atmospheric correction has to be applied,
e.g. darkest pixel method combined with
spectrally stable (in time) ground features.
Further research will focus on the latter
aspect.
Table 3. Thematic Mapper tasseled cap coefficients.
Feature
1
2
TM Band
3 4
5
7
Brightness
0.3037
0.2793
0.4743
0.5585
0.5082
0.1863
Greenness
-0.2848
-0.2435
-0.5436
0.7243
0.0840
-0.1800
Wetness
0.1509
0.1973
0.3279
0.3406
-0.7112
-0.4572
Fourth
-0.8242
0.0849
0.4392
-0.0580
0.2012
-0.2768
Fifth
-0.3280
0.0549
0.1075
0.1855
-0.4357
0.8085
Sixth
0.1084
-0.9022
0.4120
0.0573
-0.0251
0.0238
