nd
ly
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B4. Istanbul 2004
Imput Image
Histogram
Contour Image
0 5:960
0 | : "360
Hough Space Hough Space Histogram
Figure 5: Intermediate Results for a Cut of an Input Image of 1988
Table 1: Results of Building Detection
Number | Evaluated Detection | Branch
Result Percentage | Factor
| 1983 75.396 42.9%
2 1988 86.2% 36.2%
3 1988 multitemporal 82.7% 36.0%
4 2001 96.8% 37.9%
5 2001 multitemporal 97.2% 41.4%
4 RESULTS
To evaluate the multitemporal approach a building detection tool
for a GIS verification application was assumed. For this task the
region-based and structural classifier were combined. Only de-
tected building hypothesis that overlap with the class inhabited in
the region-based classification result are taken as a building (cp.
figure 7). The others are unconsidered for the evaluation.
The evaluation is based on manually segmented buildings in the
input images of 1983 to 2001 (see manually detected buildings
in the input image of 2001 in figure 7). Two measurements for
a detection evaluation described in (Lin and Nevatia, 1998) were
made:
100 - TP
detection percentage = TPT TN (5)
; 106 - FP
branch factor = TPT FD (6)
The two measurements are calculated by making a comparison
of the manually detected buildings and the automatic results,
where TP (true positive) is a building detected by both a per-
son and GEOAIDA , FP (false positive) is a building detected by
GEOAIDA but not a person, and TN (true negative) is a build-
ing detected by a person but not by GEOAIDA . A building is
considered detected if the main part (min 5096) of the building is
detected; an alternative could be to require that a certain fraction
of the building is detected.
5 CONCLUSIONS
The developed approach shows how temporal knowledge can
be used in an automatic image interpretation system. Temporal
knowledge is modeled in a state transition diagram, the probabili-
ties for state transitions are used as a priori knowledge for a linear
regression classifier.
The approach was tested on a dataset containing aerial images
acquired in 1983, 1988 and 2001. Three object classes are differ-
entiated: Inhabited area, forest and agriculture. A region-based
1247
linear regression classifier uses features like shadiness, unifor-
mity, contour angularity and straight contour lines to interpret the
images.
For the images of 1988 and 2001 temporal knowledge in terms of
a previous classification and a state transition diagram was used.
Both images were also processed without temporal knowledge to
compare the results.
To evaluate the multitemporal approach a building detection tool
for a GIS verification application was assumed. The results in
table 1 show that the proposed multitemporal approach is appli-
cable. The multitemporal result of 2001 shows less confusion
between the classes agriculture and forest than the monotemporal
result. Additional tests are necessary to measure the advantage of
a multitemporal approach in comparison with a monotemporal.
The multitemporal approach was tested in the focus of GIS verifi-
cation, other possible applications are the detection of alteration,
environmental studies, the development of urban areas and the
examination of natural disasters.
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