Racing against the incoming wet season, COWI's airborne photographers have less than two months to map an area of 275,000 square kilometres and keep an EU aid project on track. To accomplish the feat, it is necessary to fly at a height of 8900 metres (29,200 ft), a record for a COWI project.
The mapping project is a necessary part of the Namibian Government's Rural Poverty Reduction Programme, which is being funded by EU. The programme aims to develop the outlying regions of the country through a wide variety of activities, for example by establishing better infrastructure and by creation of cadastral and land registration databases. As a base for such activities, accurate and updated maps are essential.
With the wet season approaching, the mapping must be completed as quickly as possible to avoid delays to the Reduction Programme's progress. Flying so high allows aerial survey cameras to capture larger areas of data and thus speed up the process.
Project manager Jakob Riise says, "It's a challenging project. We're mapping an area more than six times the size of Denmark and we have probably not more than six to seven weeks before the rains start and stop us photographing. This is the largest mapping project COWI has undertaken in such a short timeframe."
In order to meet the challenge and beat the weather, the aerial photography is being conducted from a higher than usual altitude of 9000 metres where the aerial survey cameras aboard COWI's Beechcraft King Air aircraft capture between 800-1000 images each day during a typical five-hour flight. The previous operational ceiling for a project of this type was 6000 metres.
At the same time, five three-man ground survey teams are working one step ahead of the aeroplane, establishing ground control points every 50km in each sector being photographed. The location of the points is fixed precisely using GPS, which later on will be used to rectify the images and tie them together in a seamless orthophoto map.
"Flying so high, our new digital Vexcel cameras can capture larger areas but retain amazing detail with a pixel resolution of 60 cm. You can easily see roads, buildings, fences. You could actually count the cows in a field, if you wanted," enthuses Jakob Riise. "That said, images are quality-checked each day because of the problems haze and bush fires cause," he adds.
The flying activities began in the last week of September 2007 and approximately 31,000 images will be required to complete it. The images together with the ground control points will subsequently be passed to COWI Mapping UK for processing as orthophotos.
By Martyn GlanvillePublished: 15.10.2007
COWI's Beechcraft King Air aeroplane is a pressurised aircraft, allowing it to operate at superior altitudes. It was flown from Denmark in four days to carry out the task.
The ground survey teams faced their own challenges supporting the aerial work, including abandoned minefields on the Angolan border, flooding in the Caprivi Strip in north east Namibia, and almost impassable terrain on the Skeleton Coast to the west. In other areas, armed guards protected the teams from wild animals.