Dual baseline method enable both enlarge the width of
Interference fringes and increase the height ambiguity so that
precision of phase unwrapping and height inversion can be
improved.
5. EXPERIMENTAL RESULTS AND DISCUSSION
5.1 Land Classification Result
A generic object-based multi-scale idea is introduced to the land
classification (Corr,D.G., 2003).After the polarimetric analysis
for different lands, surface scattering fraction as feature
parameters to distinguish surface, forest, building and cultivated
lands via multi-threshold segmentation at the first scale analysis
layer. As it is sensitive to texture features exhibited in different
types orchards and crops, the two features of gray level co-
occurrence matrix (GLCM) homogeneity and dissimilarity are
selected to distinguish orchards and crops via region-based
segmentation at the following scale analysis layer. Then, merge
the two layers to generate integral segmentation image. The
each class is finally assigned at all the objects according to
image object features within a search domain. The classification
result for test areal is shown in figure.6, the 8 classes are
generated consisting of bare surface, crop, forest, building,
lychee, mango, pawpaw and areca. By the ground data
validation, the overall accuracy is up to 0.85.
hare
aie crop forest building areca lychee pawpaw mango
Figure.6. Land classification result of test area 1.
5.2 Man-made Objects Detection Result
As the Polarimetric Analysis section described, surface
scattering fraction, entropy, anisotropy are all proper
polarimetric descriptors for man-made objects detection.
Support Vector Machine (SVM) method (B. E. Boser, 1992) is
adopted to fulfil man-made objects detection with these
polarimetric descriptors. Since man-made targets are the main
object concerned, it is two classes of man-made objects and
other objects problem research of SVM method. The SVM
construct two hyperplanes that separate respectively one class
and the other class. The Libsvm library (C.-C.Chang and C.-J.
Lin., 2011) is employed with the RBF kernel of 6 = 0.5 and the
cost parameter equal to 1000.
The detection result for test area 2 is shown in figure.7. , the
most of man-made objects, e.g. the buildings and street lamps
are mostly extracted. By the ground data validation, the overall
accuracy is up to 0.89.
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B7, 2012
XXII ISPRS Congress, 25 August - 01 September 2012, Melbourne, Australia
y
po EU ta ES ‘a casses e
Figure.7. Man-made objects detection result of test area 2.
5.3 DSM Mapping
The result of ground topography mapping for the test area 3 can
be derived by a dual baseline method. Due to short wavelength
of x band data, it is feasible to map the height of the top of the
canopy rather than the height of the underlying terrain. It is
more accurate to call the map digital surface model (DSM). As
the Ground Control Points (GCP) for precision evaluation are
not available in the test area, the DSMs derived from three
different methods (MLE, ESM and the proposed method in the
paper) are compared.
The coherence map with a 9X9 pixel window are calculated,
three coherence maps from different height estimation methods
can be compared. As shown in figure.8., coherence histograms
in green, red, black colors indicates ESM method has the
highest coherence depending on its own characteristics of
coherence maximum, and the dual baseline method also has
higher coherence than MLE method because dual baseline
method implements coherence optimization processing whereas
MLE method not.
Proposed i
Sd ee €
[ ESM i
3x19 - MLE |
2x10°- |
ixurr- m" H4
us 02 94 06 Us
cohereace
Figure.8.Coherence histograms of three methods
DSMs derived from three methods can be obtained shown in
figure.9. As shown in figure.10. , histograms in green, red,
white colors show the height distribution of three methods.
Although accurate GCPs are not available, the range of
elevation of test area 3 can be searched about 20~35 meter. We
can find in the green histogram that the height distribution of
dual baseline is most approaching the true elevation of test area
3 as its peak value is close to 30 meter. Contrast with the dual
baseline method, other two methods both deviate the true
elevation range about 10 and 30 meters. It demonstrates dual-
baseline polarimetric interferometry method has better elevation
precision than MLE and ESM.
