My first job with Siegel Associates (later, Scintrex) was as a data man on one of the firm’s helicopter geophysics crews. Everything I did as a dataman was new for me -I had not a clue as to geophysics was when I started the job, but was a hard working fellow and a good learner. I am still remain grateful to the brave folk at Scintrex who took me on: Michael Lewis and Dr. Harry Siegel, the founder of the firm.
The areas to be surveyed by the airborne geophysics missions were shown on large sheets composed of spliced air photos (“air photo mosaics”) covered with parallel flight lines to be flown. On our small jobs through Northern Ontario, the flight lines could be less than a mile long and perhaps separated by 1/2 to 1/4 of a mile. On a our big projects in Northern Saskatchewan and the Arctic, the lines were many miles long. Part of my job was “flight path recovery”, which required plotting the actual flight paths of the airborne missions onto clean copies of the mosaics.
The helicopter or fixed-wing aircraft pilot, guided by the navigator, had to fly straight, at a relatively constant height a few hundred feet above the ground and over the ground indicated by the intended flight line. It was tedious work; back and forth along flight lines, maintaining steady speed and height, and then slow, careful turns at the end of the lines to start the next line over, but flying in the opposite direction. The navigator kept the course of the aircraft as close to the flight lines as he could. (Always “he”: I never met any female geophysicists or geologist staff during my prospecting years.) Navigating was difficult, since in much of northern Canada, there are a lot of trees. Billion of trees. In the Arctic there were no trees: often just tundra and bare rock with snow drifts. In fact, one bit of Canadian wilderness looks a lot like the neighboring bit. I recall one mission that we flew where we did not even fly over the client’s property, and instead surveyed some other piece of land. How did we know? Because I was the guy who plotted the actual course of the aircraft on my own air photo mosaic. But that was after I had developed the film from the missions…
The films came in magazines attached to the air photo cameras. I took the magazine into a darkroom that I had to prepare for every job. In Northern Ontario that would be the bathroom in my motel room. In bush camps we had an office built with an attached darkroom. The darkroom was made dark with black plastic. I would open the magazine in the dark, and unreel scores of feet of 16 mm film, or 35 mm film, into a garbage bucket filled with developer chemicals which I would mix from powder and water. It had a sharp smell which I can recall still. The film would stay in the developer for perhaps 15 minutes or so and then I would plunge the whole spaghetti mass of twisted film into a bucket of fixer. And then I had to wait in the dark some more, to think, sweat, sometimes singing, and all the time breathing developer and fixer fumes. I did so much waiting in the dark, that after a week or so I bought a small Hohner harmonica and learned to play folk tunes and the occasional amateurish phrase of blues. I was, and still am, a huge fan of the British blues performer John Mayall, so I probably spent a lot of time in the dark room dreaming of being a blues man.
The film had to be washed clean, and this required more garbage buckets. And then I hung the film to dry like clothes on a washing line. At camps, I let the wind and sun dry them. A clean film was shiny with no chemical residue and clearer to review. The next step was to roll the film into reels, mount the reel on a turning wheel and examine film through a lighted strip of glass.
At this point I performed the flight path recovery. The developed films contained frame after frame of trees or tundra (in negative), with the occasional bit of lake shorelines and frame after frame of lake surfaces. It took imagination and care to go through each frame and identify features in the frame which were also recognizable on the air photo mosaic. Also what was black on the air photo mosaic was white on the film, and vice versa. It was sometimes tedious, frustrating work especially if the navigator had been careless and not bothered to mark his mosaic with his best idea of where the aircraft had actually flown. Some actual flight path lines wandered across each other, across intended flight lines, off the area to be surveyed or were even duplicated lines flown along one route in one direction then mistakenly flown along the same line but in the reverse direction.
Besides the problems due to navigator errors, I also I misplotted many lines at first but the team leader, John Stewart, was a patient teacher. I soon learned rudimentary air photo interpretation, and developed an eye for pattern recognition. The skills I started learning almost 40 years ago still serve me well when I review air photographs.