They may be out of sight, but their influence is clearly seen. From scientific research to modern communication, health and emergency services, cartography, meteorology and a host of other disciplines, Earth observation satellites play a key role in various industries. Data obtained from these satellites is used in a range of tasks including mapping, land-use management, geological surveys, mining and urban planning.
One way an image is used is when a high- resolution photograph of a particular area (that has been captured by the satellite) is compared with images of the same region. Sophisticated software extracts the data needed from the satellite’s remote sensing capabilities, which is then used to create accurate maps for economic- development planning and agriculture.
Comparing different images of the same area means the accuracy of existing maps can be improved or new ones created. Changes in vegetation and the migration patterns of animals can be tracked and the effects of droughts and flooding determined. The information then influences industries such as wildlife and fishing.
Data obtained through satellites plays a major part in understanding natural disasters and managing risks relating to such events, and increases the comprehension of the Earth’s natural environment. One organisation that uses data in this way is the South African National Space Agency (SANSA). The agency’s Earth observation’s image production team has tracked specific fires by using the fire scar mapping service.
The service deals with bush fires only and does not cater to those in urban areas.
Willem Vorster, a remote sensing technologist at SANSA Earth observation, says this technology is highly relevant to South Africa as it provides evidence to solve legal disputes. ‘A legal dispute does not happen on the day of the fire or shortly thereafter. A dispute comes about two or three years after the fire event, when little or no evidence is available on the ground,’ he says.
Fire scar mapping uses satellite imagery and focuses on a specific area, depending on the client’s needs. An expert then examines the chronological sequence of the fire by collecting at least two images – one before and another after the fire. Afterwards aerial photographs are geometrically corrected and used to measure true distances. This allows SANSA’s experts to perform an image interpretation of the fire.
Fire scar mapping does not go into broader- scale monitoring and focuses only on reporting. It describes where the fire likely started and the amount of hectares destroyed. Those who can benefit from the service include law practi-tioners, farmers, insurance agents and the mining industry.
Satellite imagery and aerial photography can be used by various industries for exploration, planning and operational purposes too.
Geologists and mining management obtain information about inhabited and uninhabited areas, which helps them map vegetation and geological outcrops. This, in turn, aids environ-mental impact studies, infrastructure planning and pinpoints potential areas to explore.
Satellite imagery and aerial photography can be used by various industries for exploration, planning and operational purposes
A number of public-research organisations such as NASA and commercial satellite operators provide images. The agency’s Landsat programme and the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) imaging instrument on board Terra, their Earth observing system’s flagship satellite, are some sources of data. ASTER is a co-operative effort between NASA and Japan’s Ministry of Economy, Trade and Industry and Japan Space Systems, and its data helps create detailed maps of land-surface temperature, reflectance and elevation.
Although lower-resolution satellite images (from around 1:2 500 to 1:1 000 000) provide background imagery to site operations, higher- resolution imagery from satellites such as IKONOS Worldview-1, QuickBird and GeoEye-1 produce background imagery up to 1:2 000. Medium- resolution imagery from satellites such as Landsat and ASTER give broad-scale regional coverage.
Public and commercial data-set providers may operate their own satellites. Their role, through Geographic Information Systems (GIS) data acquisition from satellites and subsequent pro- cessing, is to make the images available for geological survey and mining purposes. The United Nations Environment Programme (UNEP)’s Geo Data Portal provides a range of online special datasets, as does the American Geological Institute’s US Global GIS database.
Meanwhile, the European Space Agency (ESA) provides imagery, among other things, via their Sentinel-1 satellite, as do numerous private companies internationally that specialise in imagery for this purpose. SANSA’s Landsat Data Continuity Mission plays a major role in this regard.
With the Earth’s population already estimated at more than 7.2 billion and steadily increasing, and more than 35% of the planet’s land masses already being used for agriculture, it’s increasingly important to make good management decisions regarding agriculture – whether on a large- scale or by individual farmers.
Sustainable farming for economic and environ- mental reasons is essential. Satellite data can be used – with information from other sources – to better manage area-specific farming practices.
Although satellites were originally used mainly to monitor crop yields, today it extends beyond this. Agriculture mapping and surveys via satellite gather information and statistics on crops, livestock and land use in general, while agricultural monitoring is applied to forestry management and to characterise forests as carbon sinks to help minimise climate change.
Then there’s precision agriculture, where satellites also make a great contribution. High- resolution images help characterise a farmer’s fields in detail. This is often combined with GIS to support intensive as well as efficient cultivation practices.
For example, different crops could be recommended for different fields, and human and other resources such as fertilisers and water could be used optimally. As a satellite constantly acquires images of the same area, assessments could be made about crop conditions based on the changing image colour within that field.
Some specialist companies such as Satellite Imaging Corporation provide satellite image data ‘at different spatial, spectral and temporal resolutions for agriculture and crop assessment, crop health, change detection, environmental analysis, irrigated landscape mapping, yield determination and soils analysis’.
The company says that images are able to show variations in organic matter and drainage patterns, while soil high in organic matter can be differentiated from lighter, sandier soil with a lower organic matter content.
A good example of an integrated project that provides data for agricultural applications and other forms of land use is the European Earth Observation Programme (Copernicus), previously known as the Global Monitoring for Environment and Security.
It uses dedicated sentinel satellites as well as some that were purpose-built for other projects, including the European Organisation for the Exploitation of Meteorological Satellites and those built by ESA member states, Canada and others.
The programme has an important, large land-management component, which includes both rural as well as urban areas, while other components look at the composition of the atmosphere, monitor the oceans and water resources, and evaluate risk management.
The GMES land-monitoring service provides ‘cross-border, harmonised geo information at global to local scales, addressing land-cover/land-use, biophysical parameters and change monitoring to support spatial planning and monitoring of freshwater, crops, forests and land carbon.’
