11
middle-resolution
gure6. They were
ry. Figure6 shows
l the commercial
Island was greater
reas was less than
ire 6 were quite
the density urban
pped. But the ISP
vere fragmentized
distortion in roll
■ the use of high-
i that the SPOT-
low to middle ISP
has been reported
>P overestimation
> similar spectral
;etation and urban
. However, this
Stic use of SPOT
InSAR_3;
attributed to the
n interferometric
sh the two land-
id in detail was
demonstrated by the ISP results of the typical area selected in
study area that located near the West Kowloon Waterfront
Promenade and covered with bared soils and sparse grass. The
spectral confusion resulted in a dramatically ISP overestimation
in the mixed area using just SPOT imagery and ISP values were
(c)
SPOT-derived ISP images represented a higher performance
(AE 15.51%, RE 0.58 and R2 0.71). As was expected, the
addition of the InSAR feature information improved the
accuracy of ISP estimate. Compared to these statistical
indicators corresponding to SPOT-derived ISP image, AE value
(d)
Figure 6 Comparison of ISP estimated results at reclamation region in Yau Ma Tei (a) InSAR_3;
(b) SPOT 4; (c)SPOT_4+InSAR_3 ; (d)SPOT imagery
up to more than 78% (Figure 6(b)), but less than 60% after
considering InSAR feature information (Figure 6 (c)).
Dataset
Statistical iiulictor
Average error
(AE) (%)
Relative
Error
m
Pearson
coefficient
m
InSAR 3
19.27
0.69
0.61
SPOT4
15.51
0.58
0.71
InSAR J +SPOT4
12.93
0.51
0.77
Table 2 accuracy assessment of ISP estimation results
In this study, a quantitative validation analysis was conducted
for the accuracy assessment of ISP estimation results.
Approximately 7252 samples were selected randomly
independently from the reference data and ISP images that
derived by using middle-resolution dataset. It should be noted
that these samples did not include those used for the ISP
prediction model development. The statistical indicators,
Average Error (AE), Relative Error (RE) and Pearson
coefficient (R2), were calculated for the three ISP images
derived from the three groups of test datasets. The results of
accuracy assessment were summarized in Table 2. The results
indicated that InSAR-derived ISP estimations were comparable
to those derived from SPOT multi-spectral images, although the
decreased by about 3 percent to 12.93% and R2 value increased
from 0.71 to 0.77. In addition, the difference between the
estimated ISP vales and reference data were calculated and
demonstrated by the error histogram. Compared with the error
histograms of InSAR-derived and SPOT-derived ISP estimate,
the one of fused data represented an apparent peak near the zero
value and more than 80% of the estimate error fell near the peak.
5. CONCLUSIONS
This study focused on urban impervious surface mapping by
using the combined multi-sources and multi-sensors remote
sensing dataset. Because of information complementarities
between optical and radar imagery, we have demonstrated that
the synergistic use of this two data sources has the potential to
improve the ISP estimate performance, especially in some areas
coved with bared soils or sparse vegetation.
In this paper, a case- study was conducted for impervious
surface mapping in Hong Kong by applying the CART-based
ISP estimate approach to the SPOT 5 HRG imagery and the
ERS-1/2 SLC SAR data. In particular, three InSAR features,
coherence, average amplitude and amplitude ratio, were
extracted from the SAR data for the investigate objective.
Validated by reference data derived from the high-resolution
CIR aerial photographs, our results show that the addition of
