On a high: scientists take snapshot of ice shelves

You would think in Antarctica, thanks to its tech-savvy contingent of scientists, that IT plays a leading role in everything the scientists undertake. Well not quite everything.

When it comes to the geographical mapping of Antarctica, modern digital camera technology takes a back seat as only well-proven analogue technology will do, says Adrian Fox, a scientist from the British Antarctic Survey's (BAS) mapping and geographic information centre.

Fox and his mapping partner Alison Cook arrived at the BAS Rothera research station in December last year for a two-month scientific mission. Shortly after they arrived, their bag of goodies did too -- 17 crates of it, consisting of a camera system and film, GPS equipment, various tripods, battery packs, chargers, generators and laptops.

This equipment BAS scientists use is all commercially available, established technology. "In Antarctica, where fieldwork is expensive, often done under logistical constraints and in narrow weather windows, it is best wherever possible to use existing, well-proven technology," Fox said. "Equipment failures can be catastrophic."

This meant sticking with analogue cameras instead of going to digital. According to Fox, digital cameras, which are comparable with existing analogue cameras, are "barely" available today. He said manufacturers such as Zeiss and Leica brought out digital systems for aerial photography in 2000, but in his opinion it will take years for these to supersede existing aerial photography cameras.

"If you think about it, an existing aerial camera with a resolution of 11 microns on a 23cm x 23cm panchromatic negative is recording onto the storage media at 8-bit -- about 0.3 GB of data, and about 1GB for 3-band colour! And it is doing it in 1/1000 of a second and can do it again 2 seconds later, about 300 times consecutively on an 80m film roll! Not bad for technology developed in the 1850s, but quite a tall order for current digital imaging technology.

"Also, considering the investment already made in aerial cameras, a new one is probably about £250,000. I think most organisations will continue using their analogue cameras for a long time yet."

When Fox and Cook arrived in early December, their first task was to assemble the camera equipment. This meant installing the main air camera to one of the Twin Otter aeroplanes used for the photography. Panels in the floor of the aircraft were removed, then the mounting ring was bolted down and the camera, a Zeiss RMK, fitted on top and looking vertically downwards. The cables were then connected from the camera to the plane's power supply and to the navigation periscope, which looked down and forwards and in the floor at the front of the aircraft.

The first area that was photographed was in Eastern Palmer Land. After that the scientists went to the Halley research station to photograph the Müller, Jones and Brunt ice shelves.

BAS geologists will use the aerial photography, and maps made from this expedition, during a fieldwork program in the area scheduled for 2003/2004 aimed at monitoring the long-term stability of the ice shelves.

The aerial photography helps by targeting the best outcrops to visit, identifying the safest routes between them, and onto them, for overland travel, Fox said.

Like many organisations involved with mapping from large format aerial photography cameras, BAS scientists have the negatives scanned, using a photogrammetric standard scanner, usually at 15 or 25 micron resolution.

Fox says a photogrammetric standard scanner has a greater emphasis in its design in the geometric accuracy of the scanning array, compared to normal ‘graphics’ scanners, which emphasise spectral/radiometric aspects. However, as this equipment is expensive, BAS contracts out its scanning, he said.

Once the photos are scanned, the map-making occurs back at BAS's Cambridge headquarters. Here ERDAS Imagine image-analysis and digital photogrammetry software is used, along with Arc/Info GIS software to compile maps/GIS data from aerial photographs and satellite imagery.

The final products are integrated into a GIS of topographic data for Antarctica. "Increasingly BAS scientists are requiring digital GIS data for their own further analysis, rather than maps, as a final product," Fox said.

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