Reminiscing about a unique traversing instrument with unknown roots.

Since my first summer surveying job in the late 1960s, I’ve never considered another profession. What drew me to surveying was the chance to work outside; what has kept me in it is the bug you get from doing work you enjoy.

As I’ve grown in the profession, I’ve always kept my eyes open for faster, easier ways of doing things. More than once a party chief told me, “Well, when you get your own crew you can do it like that!” (Of course in later years I’ve heard myself say the same thing.) But I’ve always tried to keep an open mind and consider different (and possibly better) ways of doing things. I listen to ideas from other surveyors, even new apprentices.

Innovation and invention have always been at the forefront of surveying--from the old hand crank adding machines to the modern computer. Some of the ideas have been good, some have not. Some were good for a time but became outdated very quickly, sometimes overnight. And others never managed to catch on. A few of these ideas have saved surveyors time even in light of current technology. One is the rare tracer rounds traversing instrument.

Machine at Work

In the mid-1980s, I was researching visible lasers to use for triangulation for control. I theorized that if I could see a vertical laser from several known points it would be easy to triangulate them using a 1-second theodolite. I never found the laser I was looking for but I did find a gadget that was close--and unique. It was owned by a surveyor who had spent most of his career in the logging industry. He told me that he got great closures using this instrument and that he hated to part with it (but would for a price). The price seemed reasonable to me and I got the instrument in the mail a week later.

He said there were only three of these instruments manufactured. The instrument consists of several parts. The major mechanical component is a Thompson Center Contender .45 caliber pistol with a barrel machined to fit in a steel-mounting apparatus for a tribrach. This unit then sits on legs over a point just like a transit. The pistol is loaded with a “tracer round” and fired straight up. The tracer round, a pyrotechnic bullet manufactured especially for this instrument by Chief Industries Inc. of Grand Island, Neb., consists of a brass jacket surrounding the pyrotechnic. After being expended, the hollow brass casing floats harmlessly to the ground with no danger of fire.

I bought the unit more for its uniqueness and rarity than anything else. But to see it sitting there unused on my shelf for so long was like a bag of unopened Halloween candy--irresistible. I just had to use it! The opportunity came when I was contracted for a survey in a heavily forested area of western Washington. I had a monument on a section corner down in a valley in the centerline of a road and another section corner up on a ridge. It would have taken a couple of days of difficult traversing to connect the two, necessitated by my intention to use them as my basis of bearing. I immediately thought of my rare toy. I set up my Wild T-16 on the lower section corner and sent my chainman on a hike to set up the Thompson Contender gun on the other section corner. I wasn’t sure how it would work, though, since tree canopy can make using this instrument impossible. But an ingenious feature of the instrument is that a 410-gauge shotgun shell can also be used in the pistol. With five 410 shots, we had a hole in the canopy. From then on, I just made sure I was ready when my chainman fired the tracer rounds. It took four rounds to zero in on the vertical tracer as it was shot into the sky. (The fifth was hidden by the crosshair.) With this unusual instrument, we accomplished in a couple of hours what would have taken several days of traversing. I don’t know of any other instrument (including satellite receivers) that could have done the job because of the tree canopy.

Some jobs for one reason or another get stored in your memory. This job is one of them, due to the innovation and invention of some ingenious surveyor. Thank you whoever you are.

I came across the man who sold me this instrument through one of those “I knew a guy who knew a guy” stories. Unfortunately, his name and contact information has long since been lost. I have one of the three rare instruments; the other two may be residing with some other surveyor, his children or in an attic somewhere. I would be interested to know if anyone else has one or has ever seen one. If you have, please contact me at dunawaysurveying@verizon.net.