The history of seafaring is the history of chartmaking. Without accurate charts and maps to guide them, seafarers would never survive the perils of the Atlantic Ocean. John Cunningham is part of this rich tradition. He may use modern technology to help him chart the features of Atlantic Canada's oceans, but the chartmaker's heritage is steeped in a tradition almost as old as the sea itself.

"To put it in very basic terms, we measure the depth of water," says John, 40. But, of course, there is a lot more than that to charting the oceans.

John works for the Canadian Hydrographic Service (CHS) offices housed at the Bedford Institute of Oceanography in Dartmouth, Nova Scotia.

He spends two months a year (usually May and June) on board the 50-metre Canadian Coast Guard Ship Matthew collecting data, and the rest of the year processing, cleaning up, and archiving the information. The CHS uses the data to produce nautical charts that every vessel over a certain size must carry while in Canadian waters.

John's team of six hydrographers covers all of Atlantic Canada and Labrador. On the water, four staff members conduct sounding operations from the Matthew itself, while two others go out in a pair of 10-metre fiberglass launches.

The advent of multibeam echo sounders in the late 1980s has meant that hydrographers can get a much more complete picture of the ocean floor than was previously possible. Sometimes they return to some already charted areas in order to collect more detailed data.

They frequently find dangerous inaccuracies in current charts. "Often times we find areas much shallower than an existing chart might show and we have to get that out to the public in an expeditious way," John explains. Although he still gets seasick, John says the two months spent annually in the field are by far the best part of the job. "We're always in remote areas of the country and there's not a whole lot of civilization - so it has this frontier feel to it," he says. "Flying around in helicopters is kind of neat too."