Risk Wise

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An approach to disaster management from space

Ryo-ichi Furuta, Tsutomu Yamanokuchi, Riiko Ueno, Nobuhiro Tomiyama,

Tamotsu Igarashi, and Yukio Haruyama, Remote Sensing Technology Center of Japan

he technology of satellite remote sensing has the capacity

to monitor natural disasters as well as other objectives

with the advantages of wide-area and frequent observa-

tion capability, a multi-sensor utilization environment, economic

efficiency, and objectivity. The Remote Sensing Technology

Center of Japan (RESTEC) is providing technology for the oper-

ation of Earth observation satellites, Earth observation data

distribution and applications, and training for the utilization of

Earth observation data. Currently, the Japan Aerospace

Exploration Agency (JAXA) has been operating the Advanced

Land Observing Satellite (ALOS) which is the latest Japanese

Earth observation satellite launched in early 2006. RESTEC

supports this operation under the agreement of JAXA.

The mission objectives of ALOS are cartography, disaster monitoring,

regional observation, natural resource monitoring and technology

development for future satellites. Disaster monitoring is currently

drawing attention as an important mission. RESTEC has been apply-

ing the ALOS data to monitor all kinds of natural disasters, as well

as supporting system development for disaster preven-

tion and mitigation in the Asian and Andean region. We

have also held training courses for remote sensing data

users, on a variety of applications including disaster

management. In this paper, we present the latest

RESTEC activities and discuss the effective utilization

of Earth observation data to disaster management.

Example of flood risk management for the Mekong

delta

In the Mekong delta, a large river delta in Vietnam, flood

disasters occur regularly every year. For the mitigation and

reduction of flood disasters, it is important to manage the

river basin. As a tool for river basin monitoring, remote

sensing data is effective from a wide area monitoring

capacity. The utilization of ScanSAR mode (an observa-

tion mode of SAR) is the best solution to monitor a wide

river basin in the Southeast Asian region for three reasons.

First, SAR has the capacity to observe Earth’s surface

under all weather conditions. In Southeast Asia cloud

cover ratio is usually high. Vietnam is an example.

Unfortunately, under the bad weather conditions optical

sensors cannot observe the earth’s surface. Second,

ScanSAR mode is a wide area observation mode and its

observation swath width is normally 100-400 kilome-

tres. Therefore, it is possible to cover almost every area

of interest within one observation timing. Third, it is

possible to observe the target area more frequently than

the normal observation mode without the pointing func-

tion. To reduce the effects of disasters, frequent

observation is important. Many Earth observation

Satellites adopt the 10-50 days revisit orbit. In the case

of ALOS, a 46 days revisit orbit was adopted. However,

utilizing the ScanSAR mode of PALSAR, it can observe

almost the same area every five days.

The included figure shows a colour composite image

that is made up from three images at different observation

dates. Data was acquired on 27 September 2006, 2 October

2006, and 16 October 2006 by ALOS PALSAR ScanSAR

mode. The green colour area at the centre of the image

shows that the flooded area was detected from the change

of surface backscattering. We confirmed that the detected

area corresponded to the historical inundation area. The

result was drawn using a simple analysis but we can quickly

pass flood disaster information to the end user. In a prac-

tical test, we sent the image of the flooded area through

Colour composite image of ALOS PALSAR ScanSAR

Source: Remote Sensing Technology Center of Japan

Greenery area at the centre of image shows flooded area from 27 September

2006 to 16 October 2006