The survey itself took much longer than anticipated. With Des Barres working in Nova Scotia, Holland focused his teams initially on the Gulf of St. Lawrence, St. John’s Island (now Prince Edward Island), Cape Breton Island and Newfoundland. It was in Newfoundland where Capt. James Cook cut his surveying teeth and gained the experience that earned him renown in the South Pacific. Though Cook’s exploits in the South Pacific overshadowed Holland’s accomplishments with the General Survey, Hornsby says, Cook considered him a mentor and once remarked that everything he knew about surveying he’d learned from Holland.
That first phase of surveying in Canada took five years — the time Holland had estimated for the entire survey. Holland was still at work on the surveys in the colonies when the outbreak of the American Revolution in 1775 forced him to leave New York, the southernmost point he had reached. Although the survey failed to stretch to the Potomac, the surveying parties led by Holland and Des Barres mapped about 15,000 miles of British North America from Labrador to New York.
The teams used what might seem like very basic survey tools and methods today. Flagmen set points and compasses were used to take bearings using triangulation to determine distances. Graduated chains were used to measure distances, one chain length at a time. Chronometers and quadrants established latitude and longitude.
Although the maps and charts contained some omissions and errors, they are surprisingly accurate — precise enough that UMaine geologists have used them to locate a 1760s Gulf of Maine shoreline and figure out the rise in sea levels since then, Hornsby says.