HFP Remote Sensing

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					HFP Futures Group Seminar 7
Hazard Management and the use of Satellite Imagery Professor Martin Wooster, King’s College London 25 June 2008

Satellite imagery represents a valuable tool for those responsible for dealing with humanitarian crises. Earth observation satellites can be used remotely to monitor a variety of indicators, including climate change, vegetation growth, population movements, and the destruction of settlements. The challenge now is to understand how the humanitarian community can use remote sensing technology to formulate response to disasters. What is remote sensing? Remote sensing makes use of sensors to create an image, either similar to a picture produced by a conventional camera or images in the electromagnetic spectrum. This seminar discussed satellites specifically. Satellites can measure in the electromagnetic spectrum the amount of energy being omitted or reflected by an object. Different areas of the spectrum can be used for different kinds of observation for example, to calculate population movements, destruction of settlements, or vegetation growth. The microwave region of the spectrum is used to determine soil moisture. Spectral resolution, spatial resolution, and temporal resolution are terms used in remote sensing to determine the quality and frequency of the objects that are being imaged. Spectral resolution describes the ability of a sensor to define fine wavelength intervals. The finer the spectral resolution, the narrower the wavelengths range for a particular channel or band. Spatial resolution refers to the size of the smallest object that can be seen on the ground. In a digital image, the resolution is limited by the pixel size, i.e. the smallest resolvable object cannot be smaller than the pixel size. The resolution and type of image that can be captured by the satellite is dependent upon a satellite’s orbit. Satellites operate in four key orbits – low earth orbit (LEO), medium earth orbit (MEO), geosynchronous earth orbit (GSO), and geostationary orbit (GEO). Satellites placed in LEO will typically be found at an altitude ranging between 200 and 2000 km above the earth. These satellites make one revolution of the earth every 90 minutes. Medium earth orbit is defined as the region between 2000 and 35000km above the earth’s surface. This orbital region is used by many global positioning systems. Geosynchronous orbit is when a satellite passes the same points on the earth during repeat orbits. Lastly, geostationary satellites are positioned at an exact height above the earth’s equator (about 36000km). At this height the satellite will rotate around the earth at the same speed as the earth rotates around its axis, thus appearing to remain stationary above a point on the earth’s surface. Some weather satellites and communications satellites are placed in this type of orbit because they can provide continuous coverage of the same area. One disadvantage of placing earth observation satellites in this type of orbit is the altitude.

As the satellites is so far away from the Earth it can only image large scale objects such as clouds and to a small extent large scale vegetation. Practical uses of satellites Despite the limitations of satellites they can provide a wide range of information for varying purposes as Dr. Wooster highlighted in his presentation. He noted the varying ways in which satellite data can be utilised by the humanitarian community. Currently the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) operates a series of geostationary meteorological satellites, which deliver weather and climate-related satellite data and images 24 hours a day. This information is supplied to the National Meteorological Services of the organisation's member and cooperating states in Europe, as well as other users worldwide. Food Production Remote sensing has also been utilised by the FEWS network (Famine Early Warning System). FEWS is an organisation funded by the United States Agency for International Development in 1986, to predict and monitor food security. FEWS was set up to monitor sub-Saharan African countries, however it has been extended to monitor food insecurity in other regions such as Central America. The system uses satellite rainfall analysis to measure vegetation cover and on-the-ground monitoring of local rainfall conditions in a region. Vegetation cover is measured by a vegetation index, which uses measurements of wavelengths to map out the different types of soil present. Soil reflects different amounts of light at different wavelengths and by combining the two wavelengths, maps can be generated identifying if a region is producing well or not. By measuring the different soil types in a region, it is possible to determine the amount of vegetation cover in an area. Another type of graph that is used to determine food security is “food production index”. The food production index measures the amount of food being produced in a given region. By plotting the index over time it is possible to see in what areas plants are developing. Satellites can measure the net flux of carbon from the atmosphere into green plants per unit time, which is called net primary production. The net primary production map provides details on whether a food producing region is producing below or above normal average of food. Forest Fires Geostationary satellites can also be used to determine the location of a fire by detecting the heat from fires. One such usage of satellites in this capacity was by a power company in South Africa, which used remote sensing to determine where the outbreaks of fires had occurred. Fires are costly to power companies as they cause power lines to collapse resulting in power outages. Another example of the use of remote sensing to determine fires is to determine the burning of villages. In Darfur, change detection was applied to images that were taken over several weeks showing villages that were burned.

Monitoring volcanoes Remote sensing can also be used in managing man-made and natural hazards. Professor Wooster discussed how he led a team up a volcano in Nicaragua to set up sensors on the slopes of the volcano to measure volcanic activity in real time. Information from the satellites was transmitted through the internet to teams based in a village located in close proximity to the volcano. However, he noted that there is little internet connectivity in Nicaragua making it difficult to obtain the information. A potential way to get around the lack of internet access is to receive the data directly from the satellites. Monitoring Population Movements In the humanitarian context, satellites can provide vital information when planning relief operations. As mentioned above, it is possible to determine the scale of destruction of settlements. Another application of remote sensing is the monitoring of population movements as seen in figure 11. It is possible to capture images of large populations moving between different areas. However, Professor Wooster noted that it is difficult and rare to be able to capture such images. One needs to be lucky to have the satellites facing the right time and place to capture these images. After Cyclone Nargis (3-4 May 2008) it

Figure 1

was possible to gain an initial damage assessment by comparing a pre-cyclone image with a post-cyclone image. The images (figure 22) had shown that for the areas that had been assessed, approximately 94% of all buildings were destroyed or severely damaged. The exact extent of the damages is validated by a field assessment.3 How to access remote sensing information Remote Sensing images for use Figure 2 by the humanitarian community can be gained from satellites, which are owned by individual countries or by corporations. To gain access to these images, the United Nations created the Space and
Movement of 15000 refugees N’Djamena, Chad towards Kousaeri, Cameroon. From, Jasani, B presentation 26.06.08. 2 Damage Assessment for the villages of Ongyaung & Thetkethaung, Ngapudaw Township, Myanmar. From UNOSAT website - http://unosat.web.cern.ch/unosat/ 3 For further information, please see http://unosat.web.cern.ch/unosat/asp/prod_free.asp?id=66
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Major Disaster Charter. The Charter was created in 1999 by the European and French space agencies with the aim of providing a unified system of space data acquisition and delivery to those affected by natural or man-made disasters. Countries that are part of this charter include India, Argentina, Canada, Japan, United States and China. The charter was activated during Hurricane Ike that hit Texas, USA in 2008. The space charter can be activated by any member organisation. For example, in the aftermath of the Chinese earthquake in Shanghai, the National Disaster Reduction Centre of China, activated the charter. There are programmes such as the UN Space and Major Disaster Charter that makes images available to the humanitarian community. These images are being utilised by member countries such as China to provide disaster relief. First Respondent Nick Drake, Geography Department, King’s College acted as first respondent. Nick highlighted the opportunities remote sensing can provide by giving the specific example of wildlife management in Botswana, in relation to managing elephant populations. Nick noted that through satellite images it is possible to determine where and when elephants have travelled, allowing humans to take steps to prevent humanelephant conflict. Elephant movements are determined by their need to locate food. While hunting for food, they move out of wildlife parks into villages, destroying homes. By monitoring the movement of elephants it is possible to predict when there will be food shortages. Elephants who move outside the wildlife parks in search of food indicates the coming of food insecurity. Conclusions Remote sensing provides humanitarian workers a tool for planning relief operations. These images can also aid our understanding about where future disasters may occur. Already, satellite images are being used to determine food security through the measurement of rainfall and the growth of vegetation. One participant, noted how in a recent flood emergency in Africa, satellite images were used to locate the best routes for moving aid into the country. Remote sensors have numerous applications for the humanitarian community, however before their capabilities to be fully utilised, there needs to be an increase in dialogue between humanitarians and technical experts. Humanitarian workers need to gain a deeper understanding of available space capabilities and technical experts working within the space field need to be aware of how this technology could be applied in the humanitarian context. For further information on the seminar series, please contact: Rosie Oglesby Programme Coordinator Humanitarian Futures Programme King’s College London Strand Bridge House 138-142 Strand London WC2R 1HH Email: rosie.oglesby@kcl.ac.uk Phone: 0207 848 7271


				
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