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Major Technology Trendus and Their Impacts
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A Study of Areospace Reconnaissance of Earthquake Sites
Advantages
- Request capturing imageries within 1 day (all available high resolution satellite data to be considered) make survey of
short-time-sequential changes possible.
- Digital imageries are delivered in a few hours after capturing imageries through online data supply and available in the
early stage of disaster.
- Imageries cover large area at a time and are suitable for investigation of global damage.
- Nadir imagery can be regarded as good approximation of orthophoto because the satellite captures imagery at very high
elevation with long focal length.
- Time sequential imageries can be stored in database and applied to GIS systems for assessment of damage.
- Analysis of spectralcharacteristicsof image enables extraction of liquefaction area.
- Data ru-eavailable for low price.
Disadvantages
- Imagery data tend to be affected by clouds.
- Availability of imagery data at specific moment depends on satellite position.
Potential of the high resolution satellite imagery satisfies the requirement for aerospace reconnaissance in
the early stages of disaster. It is expected that satellite imagery will supplement the role of aerial
photography when they are not available and/or when global damage information is required, while aerial
photography will provide information with a high accuracy requirement.
INTEGRATED IMAGERY SUPPORT FOR DISASTER STAGES
Through the discussion described above, it is clarified that aerial photography provides an information
resource which meets the requirement of high-accuracy analysis such as investigation of accurate damage
situation and measurement of geographical displacement, where accuracy has a higher priority than
processing time. They also can be used for obtaining information in the area which could not be captured
by satellite sensors. On the other hand, high resolution satellite imagery has the advantage of wide area
coverage and instantaneous online data delivery. It can effectively used for rough estimation of damage
conditions in the early stages after a disaster. It also can be used for analysis of changes of the site before
and after the disaster by using time-sequential imageries.
Table 4 summarizes our discussion. Satellite imagery databases can be used to assess damage before
earthquake with other geographic data. For this application, it is indispensable to update continuously
geographic data such as soil type, building type, and simulated results of seismic intensity. A satellite
imagery database itself is also used for ordinary GIS data.
Fig.4 Comparison between contours of criterion data and calculated data
Naturally, imagery resources obtained via aerospace reconnaissance can not provide all of information in
demand. Detailed information such as investigation of casualties and some of relief activities should be
supplemented by field survey. Online integration of information obtained by satellite imagery, aerial
photograph and result of field survey facilitates the planning for required resources on demand. Multi-media
communication technology will enable such an online information system.
Summary
This paper discussed the effective utilization of image resources for earthquake sites. Aerial photography
can provide more accurate spatial data than can satellite imagery, while satellite imagery has more instant
availability than aerial photography. Therefore these image resources can be used together in a
complementary fashion to effectively help damage reduction and quick restoration of the earthquake sites.
There is no prevention against earthquakes. Therefore, our effort must focus on prevention against damage
caused by earthquake. Is it possible to provide imagery information on demand and analyze it
instantaneously? This is a large demand on data providers. All providers of aerial photographs should
ensure that their systems address the needs discussed in this paper.
Table 4 Imagery Information support of damage situation by aerospace reconnaissance
References
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