By Peter Rejcek
Sun staff

According to his GPS unit, Tom Holford's CAT Challenger chugs along the sea ice at a steady 16 kph on a near windless, cloudy day en route to Cape Evans from McMurdo Station. A low, solid sheet of clouds flattens the horizon, skewing the heavy equipment operator's perspective of the landscape.

The train he's pulling includes a 9,000-kilogram tracked drill rig, which bores 1.2-meter-wide holes in the sea ice; a sea ice hut on custom-welded skis; and a third sled carrying the 270- kilogram auger for the drill. Shovels, heavy wrenches, a pry bar and hand drills complement his equipment list.

But perhaps one of the most important tools for such excur sions sits on his dashboard next to a small fan blowing against the windshield to prevent the cab from fogging - that hand held Garmin 12XL GPS.

"I use it on a daily basis," said Holford, whose primary job for much of the season is sea ice science support. It's a job that involves everything from dragging fishing huts around ice crisscrossed with small cracks to drilling holes for science teams to use for their various projects.

Holford is one of many U.S. Antarctic participants who regularly uses a GPS unit for different operations around the continent. The landscape he moves through is deceptively static: A few blackened features interrupt the frozen sea like rips in a blank sheet of paper - Little Razorback and Big Razorback islands to his right, Tent Island looming just ahead. Weddell seals lay like bloated sea slugs on the frozen ocean surface near the Erebus Ice Tongue.

But cracks can abruptly form and rollers may erupt along established routes, looking like frozen waves poised to break on a white beach. No matter where he's going or what he's doing, the GPS is tracking his movements, gathering data that's used in a variety of situations.

"We log all that information - hut location and the holes we drill," Holford explained. In fact, the GPS unit's waypoint list reads like a geography book index of the sea ice. A waypoint is a specific location of latitude and longitude, such as the coordinates of a sea ice hole.

Back in his office at fleet operations, Holford can download his findings to a computer and add them to a database. With GPS becoming more commonplace, he now has several years of history to draw upon. The record includes information on past locations of science camps and sea ice road routes. "[GPS is] being used more and more here," he said. "The technology is only getting better with the GPS units."

Tracking the trend

The trend to use GPS on the job site has spread throughout Antarctica. Some uses are fairly obvious, such as for search-and-rescue operations and land surveys for the airfields. In other departments, the function isn't necessarily intuitive, but makes sense and quickly permeates the way they do business.

The environmental, health and safety department, for example, records GPS coordinates of soil sampling areas in McMurdo and the location of non-established helicopter landing sites in the McMurdo Dry Valleys.

"We're keeping a database of disturbances," explained Cindy Dean, EHS environmental educator.

A new use involves the Antarctic Specially Managed Area in the Dry Valleys. The ASMA designation, which went into effect last year, codifies more stringent environmental guidelines for a 15,000-square-kilometer swath of the area.

Part of the new modus operandi is to record GPS disturbances as seemingly benign as staking a tent in a previously unestablished area.

Kaneen Christensen, Raytheon Polar Services Co. environ mental engineer, said her department recorded about 20 science events in the Dry Valleys last year. Events involve anything from sample locations to tent locations to helicopter landings. There are almost a thousand individual points within the valleys, she said.

"Limiting impacts to the delicate soils of the valleys is important in sustaining the soils," Christensen said. "Tracking disturbance information, in theory, will allow us to determine what areas have been subjected to multiple disturbances. As the practice of tracking disturbances becomes more ingrained, recordings are likely to go up in numbers in the Dry Valleys and elsewhere."

Events logged by EHS can vary from five to more than 200 waypoints, she added, with location data dating back to 1996. GPS units are also issued to all science teams by the Berg Field Center, the REI-like warehouse of science support.

"Any scientist who is coming in is probably using one," observed Karla College, BFC supervisor. She said there's been a marked increase in the number of units the BFC has in its inventory. In 2002, there were 80 Garmin GPS units and five older Magellan models. Today, the stock includes about 160 different Garmin GPS models.

The bigger picture

Before 1994, locating the next spot for the shifting geographic marker at South Pole every year wasn't exactly Stonehenge mysticism, but neither was it as precise as it is today thanks to GPS technology.

Larry Hothem, with the U.S. Geological Survey, went to the South Pole Station earlier this month to reset the marker using high-precision GPS, which provides accuracy within a centimeter.

Before that, Hothem said the Pole was located by Doppler Satellite Positioning, which is accurate to about a meter. Because of the motion of the ice, the geographic pole slides about 10 meters a year, heading in the general direction of the Dome.

This year locating the pole marker will be a little tougher because it's being done much earlier than normal. Hothem usually arrives at Pole shortly before New Year's Day, when the new marker created by the previous winter crew is unveiled and set in its new location. This time he will have to project forward the location based on calculations taken in October.

Hothem had a couple of other projects to do at Pole, including relocating a GPS receiver system from on top of the Skylab building to the new elevated station.

"We're among the last to leave the old facility as I understand it," Hothem said.

The South Pole, like McMurdo and Palmer stations, serves as a reference station in a global network of stations called the Global Navigation Satellite Systems (GNSS). The reference station data are used in computations for the precise orbital coordinates for the GPS satellites, for scientific research such as mapping changes in the ionosphere, and for conducting real-time GPS positioning, according to Hothem.

"[Pole is] a very useful station for evaluating the predicted satellite orbits that are included in the message broadcast to users such as those mentioned earlier. Though the station is moving at a constant and predictable rate, the station serves as a reference station to compute long-range coordinates to other points," he said.

Back in McMurdo

As one often hears in contexts both serious and lighthearted, Antarctica is a harsh continent. When the winds start to blow or the clouds create a disorienting landscape, an additional safety net is valuable.

Again, the GPS unit is handy. When returning to McMurdo on the sea ice road that Holford had tracked on the GPS earlier, the tractor icon on the unit's screen runs along the same black line it had spun earlier. Holford said that the GPS can be an invaluable tool for keeping out of trouble away from station, as it "drops digital bread crumbs" behind his tractor rumbling along the sea ice.

But he cautioned that the GPS isn't a substitute for good visibility. "Using your head is the No. 1 tool," he said.

A GPS was used to help layout the ice road to Marble Point, near the sea ice edge. The 16-hour traverse can be brutal on both machines and operators. By study ing last year's coordinates via helicopter, it was determined that the old route was probably the best to use, according to Holford, saving some wear and tear on people and equipment. "It's getting rougher every year," he said of the multi-year ice with its melt pool voids, saline pockets, deep snow and sastrugi. "It turned out last year's route, in gen eral, was the best we could do."