Bird’s-eye view offers inside track

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Mapping South Africa’s capacity for farming is getting easier thanks to Earth observation.

Two maps of South Africa sit side by side, each telling a very different story of the country’s agricultural potential.

The 2010 land capability map of Gauteng — which gauges the soil, terrain and climate of the area with respect to agricultural potential — looks like army camouflage, a mottled collection of greens and browns that indicate “high” and “extremely high” potential.

But the 2010 agricultural zones map of the same area is riddled with red and flesh-coloured blotches, showing the province’s residential and mining areas.

The former was developed through physical surveys and measurements, says Anneliza Collett, production scientist at the department of agriculture. “It looks nice on paper, [like] a high-potential agricultural area.”

The other map used satellite imagery and “you can see what’s going on. Driving around [for physical surveys] you can only see on eye level. With satellites, you can see from above … I can’t imagine the days when we didn’t have [this imagery].”

The imagery comes from the Spot-5 satellite, which stands for Système Pour l’Observation de la Terre, or system for Earth observation. Spot Image, the company that runs the Spot satellites, is based in Toulouse, France. The South African Spot-5 2012 mosaic was launched earlier this year. “We have been collecting this data for the whole of last year … it is something we do annually and distribute to 30 to 40 national and provincial government departments,” says South African National Space Agency (Sansa) chief executive Sandile Malinga.

The mosaic comprises 485 images that were processed and compiled to make up the map of the country, Sansa said.

There are two pieces of legislation that Collett’s unit manages: the Subdivision of Agricultural Land Act and the Conservation of Agricultural Resources Act.

“In both, we use Spot imagery … It gives us a bird’s-eye view so we can see what’s going on and [can] see changes over time.”

If the area of agricultural land is too small, it becomes difficult to farm, she says. “We do not want to subdivide the land until it is not viable [for farming].”

Collett refers me to the 2010 agricultural zones map. “All the red spots are the built-up areas. If there are small dots of green, it becomes difficult to farm.” But, at the same time, “farming must not degrade natural resources”.

The satellite imagery means that Collett’s directorate can see the changes in land usage over time, identify cultivated areas and estimate yields, and hone in on areas where these Acts are not being enforced. Also, physical surveys, which involve a specialist driving to the area and conducting a soil survey, for example, are expensive, but through satellite imagery these areas can be surveyed from the sky.

Collett says “there was a time when we were not sure about Spot”, when the agreement was signed in 2005 for South Africa to buy the Spot-5 images, “but [now] the Spot-5 images help us tremendously”.

She cannot speak for other departments, but says the satellite imagery is part of “every decision, every recommendation”, and the main focus is on ensuring food security.

Tom Vorster, deputy director for forestry information systems in the department of agriculture, says that his unit uses the Spot-5 images to map the country’s indigenous forests and commercial plantations.

“We get the images every year … so it is updated and you can check if there have been changes in the natural forests and commercial plantations.”

Vorster says: “We don’t have a lot of natural forests left in the country — just more than 500 000 hectares. We need to try and protect them.

“It’s quite a huge task because [we have to look at] the whole country, but the technology is definitely improving and that’s a great help.”

The department of human settlements uses Spot-5 to detect urban sprawl and map the spread of human settlement, but the Mail & Guardian’s repeated attempts to contact its communications person were unsuccessful. The demand for satellite imagery in government departments bolsters the case for a home-grown Earth observation satellite, which is expected to go into the development process in the next few months.

At the science and technology budget vote in Parliament in May, Science and Technology Minister Derek Hanekom pledged R272-million over three years for the development of a new satellite, which has been named ZA-ARMC-1. “The satellite will greatly enhance Africa’s ability to monitor and manage its precious natural resources,” he said.

ZA-ARMC-1 is South Africa’s contribution to the African Resource Management Constellation. In 2009, four African countries — South Africa, Nigeria, Algeria and Kenya — committed to contributing at least one satellite to the constellation, which will monitor resources such as agriculture, water, climate and human settlements.

Nigeria already has two satellites, one of which is part of the constellation. South Africa did have a R25-million low Earth-orbit satellite, which it built, but after a difficult two years in space the beleaguered pathfinder finally lost power in 2011.

Requests to Sansa regarding how much the agency pays for Spot-5’s images were unanswered. The M&G had previously been told that a licence to access satellite images for three years cost about R80-million.

Three important arguments for a South African-operated satellite are that the country will no longer have to buy images from other countries; it will gain Earth observation sovereignty as other nations will not be privy to what the country is monitoring; and that South African stakeholders could decide what the satellite needed to take images of.

“The new satellite will definitely help,” says Vorster. “We are in contact with Sansa all the time, so when they have workshops and planning sessions, they involve us [regarding] our requirements [from the new satellite].”

Collett becomes more animated when she talks about the image possibilities when the country’s new satellite comes online. “A seamless mosaic could be taken at different times of the year, we can have crop monitoring in real time. Farmers want to monitor [their crops] during the growing period, and we can ask what [they want] to look at.”

Last week, Sansa opened its call for project proposals from South African companies, academic and scientific institutions and individuals to use Spot-6 imagery. Spot-6 was launched last year, and offers higher-resolution images than Spot-5.


SARAH WILD is a Rhodes University graduate

Article Source: Mail & Guardian


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