Torlegärd et.al (1984), are used. The result is summarized
in Table 1.
Table 1. Karhunen-Loeve expansion of the average correlation
funetions of the six ISPRS DEM test areas.
Uppland 8 = 0.625 CP + 0.044 a, - 0.046 d;
Bohuslün c = 0.698 à, - 0.099 3, - 0.002 d;
Stockholm © = 0.522 à, * 0.128 q, - 0.055 à,
Drivdalen 2 = 0.865 9, :719.287 d, + 0.001 dz
Sühnstetten € = 0.317 §; + 0.503 3, - 0.053 à,
Spitze 7 ='0.567:4, + 0.175 7 + 0,204 dz
Variance (Ay /In) 85 % 15 % 2 %
The variances in Table 1 are calculated using the
eigenvalues Ak? and are measures of the significance of the
base functions. They should be read in such a way that by
using the first two base functions, 98 % of the correlation
functions can be recovered.
When comparing the different terrain types, some main
differences of the coefficients of the first and most
Significant base function d, can be noticed. The two German
areas (Sühnstetten and Spitze) have here a rather small
coefficient, while the Norwegian area (Drivdalen) has a
fairly large coefficient. The three Swedish areas have a
first coefficient somewhat between the steep Norwegian area
and the smooth German areas. The two base functions d4 and
q, are shown in Figure 1.
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