Utilizing Satellite Images for Comprehensive Urban Disaster Relief

Atsushi Takeda

Tohoku Bunka Gakuen University 6-45-16 Kunimi, Aoba, Sendai, 981-8551 Japan
E-mail: atakeda@ept.tbgu.ac.jp

Abstract

For urban disaster management in an emergency, fast information about damage to public facilities such as roads, bridges, railways and so on will be absolutely necessary. So far as this application is concerned, conventional satellite images have been useless. But information gained by satellite has the potential for assisting quick aid and rescue management of disasters occurring beyond national border.
In this study, the feasibility of the application of 1-meter ground resolution images by the recently launched IKONOS satellite is examined for the case of the 1995 Kobe Earthquake. IKONOS 1-meter resolution panchromatic images, overlapped with 4-m resolution RGB image over the several sites where typical damage is seen in the air photos taken just after the event, are selected and compared with the air photo images at the same reduced scale.
The result was the clear identification on the IKONOS images of traces of earthquake damage, such as a fallen bridge, a derailed train, fires, fire ruins, collapsed wooden houses and large cracks on reclaimed. The confused situation after the disaster, such as traffic jams and tents for the displaced, are also recognizable on the images.
It is concluded that traces of major damage in an urban disaster could be extracted from the 1-meter resolution image overlapped with RGB images.

Keywords: Satellite images; Urban disaster


1. Introduction

A devastating disaster occurring in city areas densely populated will bring a tremendous loss of lives and properties. In order to reduce the losses and to prevent the spread of damage after a disaster has occurred, fast rescue and relief from outside of the stricken area is required. Here, precise information relevant to the current situation at the disaster site is needed by all to support activities of disaster relief.
Typically, large-scale damage that comes with an urban disaster includes the destruction of such public facilities as roads, bridges, railways, public buildings, airports, harbors and other various lifelines.
The damage to these public facilities, and the fires and debris caused by the disaster, are local and very small scale events individually, but when occurring simultaneously, can greatly interrupt the rescue and relief activities of the entire stricken area.
An important point of disaster management for an urban area is how to get the relevant information on facility damage and obstacles distributed in a short time, and how to make a plan of action for the relief activities. For quick information gathering in these cases, air survey is considered to be a powerful and effective method.
In Japan, airplanes and helicopters of governmental bodies fly over the relating areas immediately after such an event occurs. At the same time, private air survey companies make aerial photograph surveys all over the area within a few days and sell the pictures to the concerned organizations. These may be most convenient methods for photograph data within Japan.
For the disaster beyond a border, however, the situation is quite different. Today, Japan is frequently requested to dispatch help for emergency rescue in overseas countries and Various regions. Usually, the occurrence of a disaster in foreign countries is reported first through mass media. But such media reports have a tendency to be fragmentary and to not provide an overall view of the event. Before dispatching, information is needed on what kind of public works are inoperational, what kinds of technologies are being called for, and what routes are the shortest to reach the affected sites.
Generally it may be too late by the time that official, precise information is sent from the country concerned. In such cases, satellite remote sensing will be looked to for providing the information needed.

2. 1-meter resolution satellite images

In the past, available satellite images of the earth's surface, except those for military use, have not had a sufficiently high resolution to identify traces of damage, which is important for monitoring urban disasters. Then in 1994, the U.S. government finally approved, with some restrictions, the use of military high-technology by certain civilian organizations.
As a result, the IKONOS satellite carrying a 1-meter resolution panchromatic sensor was launched in 1999 by Space Imaging Company of the United States. IKONOS is now on a solar synchronous orbit at a 680-km altitude, with an 11-day regression period. The frequency of observation at a point is 1 time per 3 days for 1-meter resolution and 1 time every day for 2.1-meter resolution. The panchromatic sensor consists of a linear array of about 1/14000 CCD covering a band 0.45-0.90 m, and a multi-band sensor consisting of a linear array of about 1/3500 CCD covering the 4 bands of B, G, R and NIR.
It was tentatively determined that an IKONOS image could necessarily identify the damage that commonly occurred in the Great Hanshin-Awaji Earthquake.
Fortunately, in February 2000, IKONOS could observe relatively clearly the almost-recovered city of Kobe. The IKONOS images were compared with air photos of the same scale taken by Asia Air Survey of Tokyo just after the earthquake happened on January 17, 1995. In this paper, a brief comparison is provided of the basic results offered by these pictures.

@

3. Some result

Three sets of air photos of a typical urban disaster point in the Hanshin Earthquake area and a recent IKONOS image of the same location are shown below.
The resolution of each air photo is reduced to 1m in order to simulate the IKONOS image, in which the damage or the unusual matter is still visible.
If IKONOS is to be used to observe a scene in real-time, then it must be caught in the image and obvious to simple visual extrapolation.



Case 1. Destructed Overpass and Fallen Bridge


                         Air photo showing the damage


                                IKONOS image today


@

Case 2. Fires Caused by the Earthquake


                                Air photo showing the fires

@


                                     IKONOS image today

@

Case 3. Traffic Jam on Highway

                         Air photo just after the earthquake




                                     IKONOS image today


*The IKONOS images are presented here by courtesy of Japan Space Imaging
and the air photos are by courtesy of Asia Air Survey .