Launch of 2013 SPOT 5 national mosaic

September 10th, 2014, Published in Articles: PositionIT


The South African National Space Agency’s (SANSA) Earth Observation directorate launched the 2013 SPOT 5 National Coverage Level 3 and National Mosaic imagery on 5 September 2014. It also for the first time released SPOT 6 National Coverage Level 3 imagery, which still needs to processed into mosaic imagery.  Various representatives from the user community were in attendance including representatives from national and provincial government, parastatals, NGOs, science councils, and tertiary education institutions.

SANSA’s data, products and services manager Aubrey Kekana provided an overview of this latest release. The annual SPOT 5 imagery has been available through SANSA since 2006, with the 2013 imagery acquired from 10 January to 31 December 2013. The National Mosaic is an annual 2,5 m resolution natural colour composite of SPOT 5 satellite imagery, covering the landmass of South Africa. SPOT 6 provides even higher resolution 1,5 m imagery, and along with SPOT 7 will replace SPOT 5 in mid-2015. SPOT 6 National Coverage data is also being made available.

SANSA senior Earth Observation staff and other speakers (Adri de la Rey, Mercy Matheri, James Aphane) on the day of the 2013 SPOT 5 and SPOT 6 imagery launch.

Senior management, SANSA Earth Observation personnel and speakers at the imagery launch.

The SPOT 5 National Coverage Level 3 imagery consists of 1932 ortho-bundled images (panchromatic, multispectral and pan-sharpened images), and the Mosaic National coverage consists of 548 RGB image tiles. The 2013 SPOT 6 ortho-bundled package include 1062 scenes (531 panchromatic (1.5 m), and 531 multispectral (6 m)).

Both satellite imagery sets use quarter degree tiles and WGS84 Transverse Mercator projection, and are packaged with documentation and metadata, and shipped in a compressed Geotiff format on hard drives. The Level 3 imagery is generally considered most suitable for remote sensing purposes, and the mosaic imagery for cartographic applications.

Plans are currently underway to create the SPOT 6 National Mosaic. Kekana believes that SPOT 6 with its higher resolution will bring about new applications as well as new customers, most likely in local government and the private sector. SPOT 6 and 7 also eliminate latitude conflict, and will offer six mission plans per day, compared to SPOT 5’s one a day.

SANSA’s Dr. Jane Olwoch explained that obtaining the imagery directly form SANSA is the most cost effective option for organisations, as SANSA has a DRS Agreement with Airbus Defence and Space Systems, operators of the SPOT satellites. Also speaking at the event, SANSA CEO Dr. Sandile Malinga discussed new satellite trends, such as the uses of smaller satellites in flocks, and the need for radar on satellites to make observations during the night and on overcast days. Mmboneni Muofhe, deputy director-general for research, development and innovation at the Department of Science and Technology, also emphasised the importance of skills and capacity in the processing and interpretation of the data to extract the most from space products.

SPOT 5 imagery applications were highlighted in three presentations, delivered by Eskom’s Adri de la Rey, Mercy Matheri from Statistics South Africa, and James Aphane from the Independent Electoral Committee (IEC). De la Rey explained how the utility uses satellite imagery in their GIS for planning, growth rate analyses, route and site selections, load forecasting, and power line and risk management. Mercy Matheri explained that StatsSA uses the imagery mainly for change detection and in their Dwelling Frame, while James Aphane described SPOT 5 data as a quality and enhancement tool, and illustrated how the IEC uses the imagery in combination with cadastre and other data for accuracy checks in the planning of voting stations and operations.

The second session of the launch was dedicated to SANSA’s value added products; specialised analyses carried out on SPOT 5 imagery to extract different layers and meaning. SANSA’s Nale Mudau showed how the National Human Settlement Mapping layer works, a built-up layer that was created using Morphological Textural Radiance on 2012 SPOT 5 imagery. This layer characterises built-up structures into four categories, and allows for building density studies, change detection and urban growth studies, for planning, and for accuracy checks against demarcation data.

Willard Mapurisa spoke about value added products such as the TOA (Top of Atmosphere), and the Brightness and Temperatures products, as well as radiometric indices such as the 30-day Normalised Difference Vegetation Index (NDVI) and Normalised Difference Water Index (NDWI). SANSA also offers a medium resolution (30 m) 30-day water bodies layer, and 12-month high-resolution (6 m) water bodies layer.

Dr. Clement Adjorlolo concluded the session with a look at products for natural resource inventory and assessment, which can be used for agricultural zones and land-cover classification, cropland monitoring, bush encroachment and bush thickening studies, and modelling grazing and browsing capacity, among other things.

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