Mapping the Canadian North – Post WWII

By Neil Taylor

Prior to the Second World War, one of the principal responsibilities of the Canadian Air Force was aerial photography. It was a slow process, given the aircraft and camera equipment of the times, and during the entire period from 1921 to 1939 only 868,600 square miles of territory were covered. With the advent of the war, domestic aerial photography for mapping purposes was discontinued.

As the war wound down, the RCAF moved to re-implement its aerial mapping program, paying particular attention to the Canadian North where accurate mapping was almost nonexistent. Three B-25 Mitchell light bombers were purchased and retrofitted with special cameras developed by the National Research Council for use in the development of Topographic Air Navigation Charts.

These Mitchells were based at No. 22 Photo Wing, Rockcliffe, Ontario, which consisted of 413 and 414 Squadrons with three Spitfires, a Hurricane, five Ansons, a Canso and a Norseman assigned to photographic and supply operations. After some initial experimentation, a new mapping program officially got underway in 1945.

413 Squadron B-25 Mitchell (courtesy Ron Dupas,

Two types of aerial photos were taken – vertical, employing a single directly downward looking camera, and trimet, utilizing a combination of three cameras – one pointed vertically downward and the other two mounted obliquely pointed in directions perpendicular to the direction of flight. The trimet system, through simultaneous exposures, enabled photographs from horizon to horizon of narrow strips of ground. This enabled the coverage from a single flight line to be greatly expanded, thus requiring fewer flight lines when photographing vast expanses of territory.

The season for aerial photography in the Canadian North was short since ground needed to be free of ice and snow, and it could be further hampered by cloud cover and smoke from forest fires. The small airplanes were unable to cover much territory so in 1946 the Ansons were phased out and the Mitchells along with a few Lancasters assumed the lion’s share of the work.

That same year, a very controversial program of the United States Army Air Forces, called Operation Polaris, began in the Canadian Arctic. It involved three round trips per week between Meeks Field, Iceland and Ladd Field, Alaska for the purpose of improving air force operational capabilities in the far north, the likely battleground in the event of a Soviet air strike on North America. Flying in the Arctic was difficult due to adverse weather conditions, unreliable magnetic compasses and the lack of accurate mapping. Through these regular transport flights, the United States hoped to gain valuable information on northern operations.

The Government of Canada granted approval for the transport flights in 1946, but the following year it learned that the Americans were surreptitiously taking aerial photographs during these flights. The Canadians feared the Americans were searching for undiscovered islands that they could claim for their own thus undermining Canadian sovereignty in the north. Diplomatic objections were filed and eventually the Americans admitted to the illicit aerial photography and agreed to suspend all such activities.

Meanwhile the Canadian aerial photography program was gaining momentum. Using the available Lancasters and Norsemen, the RCAF surveyed approximately 130,000 square miles of Arctic territory by March 1947.

In 1949, the RCAF formed 408 Squadron at Rockcliffe and equipped it with eight modified Lancaster Mk 10 aircraft. Two of the biggest modifications were removing the rear turret and replacing it with 600 pounds of ballast, and adding SHORAN equipment. These Lancasters then assumed primary responsibility for Arctic mapping assisted by Dakotas in the other two squadrons.

408 Squadron Lancaster being refueled. (Courtesy of Directorate of History & Heritage)

SHORAN (Short Range Aid to Navigation) greatly improved the accuracy of the northern mapping program. Ground stations with radar transceivers were established at various points throughout the north. The SHORAN-equipped Lancasters transmitted airborne radar pulses to a pair of ground stations and measured the time differences between the two return pulses. This enabled the aircraft to determine its exact position relative to the ground stations. In turn, the aerial photographs taken could then be accurately fixed against the ground locations.

The aerial photography program continued to expand. In 1949, 870,000 square miles of northern territory was photographed and mapped. The following year another 869,000 square miles was covered. The aerial photography had its advantages, in 1948 a flight over the Foxe Basin off the southern coast of Baffin Island discovered two uncharted islands which added 5,000 square miles of new territory to Canada.

By 1950, 408 Squadron was given full responsibility for Arctic patrol work and three of its Lancasters were modified to Mk 10AR (Area Reconnaissance) through the addition of extra fuel tanks, new camera systems and search radar.

408 Squadron Lancaster flying “lines” over Ellesmere Island, NWT. (Courtesy of Directorate of History & Heritage)

By the end of the 1950-51 photo season, the RCAF had surveyed the vast majority of the Canadian North. The Lancasters of 408 Squadron, and later commercial operators, would continue to fill gaps in the aerial coverage, but increasingly the squadron’s attention turned to Cold War northern reconnaissance patrols aimed at monitoring Soviet activity in the Arctic and collecting atmospheric samples after Soviet nuclear tests.

In less than a decade, while overcoming extreme environmental, operational and technical constraints, the RCAF had completed one of the most ambitious aerial mapping programs ever attempted. The results have helped open up the North, pave the way for today’s airline polar routes and support Canada’s sovereignty in the Arctic.