What’s a Slide Rule, Dad?
Image via WikipediaOver on the skunk-works blog I’ve been doing a few posts on the dangers of convergence in technology. My assertion there is that many of our technologies should be redundant, otherwise we have made ourselves vulnerable by putting all our eggs in one basket, so to speak.
What I’d like to do here is the opposite ie chronicle changes in a field that I have personally been a part of. That field is surveying, and specifically the production of topographic maps.
So cast your mind back, if you can to 1965. My first summer job in Canada was working for the Water Rights Branch of the Ontario government, producing topographical maps of various drainages around the province. And remember, there was no digital technology at all in those days, not for general use, anyway. The biggest corporations and branches of government had big, hulking IBM mainframes that operated mostly by sorting punch cards. A 16k memory module was the size of a phone booth. There were no calculators. No personal computers. One of the big controversies in my high-school when I was in grade 13 was whether slide rules should be allowed in exams. The consensus, by the way, was that they shouldn’t be allowed because that would constitute cheating. If you solve the problem with a slide rule, then you don’t really have to understand it. Or something like that. It never really made sense to me.
Now, a topographical map is really a pretty simple thing. To generate one you simply have to be able to establish the height above sea level of a series of points covering the area in question, then deduce and draw in the contours by interpolating between the heights of the points you had established. Like I said, pretty simple.
The process in the field was a bit more complicated, consisting of a surveyor with a theodolite and one or more ’stadia rods’. The theodolite was set up in a central location and a shot taken back to a baseline and the elevation of the instrument was established. Actually, it was a lot more complicated than that, but let it go. Once you had the baseline and the elevation established, it was then possible to define any point you wanted to record by the angle between the baseline and the point. Distance was calculated by how much of the rod was visible between two hairs in the telescope. Then there would be a vertical angle recorded. All these readings would be written down in the surveyors notebook and the rodmen would then move to other points and the process repeated. The art was in getting just enough readings to allow the contours of the land to be interpolated without burying yourself in calculations.
Don’t forget, each ot the readings I was talking about were raw data. At the end of the day, or week the fieldbooks were transported back to the office to be ‘reduced and plotted’. That consisted of converting all the readings to actual points of elevation and bearings which a draftsman would then plot out on a large piece of paper. The calculations were performed by looking up factors in a book of tables and then actually calculated using a hand-cranked adding machine. Only when the points had actually been plotted was it possible to see if there were any ‘holes’, that is missing data which would mean going back to the site and getting more readings to fill in.
If this seems like cumbersome work, it was. However, it was also healthy, outdoor work. We got to travel and meet lots of girls and all expenses were paid for the summer, so things were cool.
A couple of years later, I got a job as a draftsman working for Ontario Hydro, again doing topographical maps. What changes had taken place in those two years. What changed? Two pieces of technology came together. One was the calculator. By those days they could do trigonometry, so the calculation of the elevations became fairly trivial. The other was the portable FM radio, basically a walkie-talkie with a range of around ten miles.
The process of mapping was pretty smooth. One instrument was still set up but they used multiple rodmen and one shot could be taken while the others moved into position for the next. Instead of writing the readings in a notebook, they were dictated into the radio. I was sitting in the office with the second radio. As soon as a reading came in, I would write it down, then calculate the actual distance and elevation using the whiz-bang smoking gizmo from Texas Instruments. Then I would plot it on the map. Still by hand, but hey, way cooler than it used to be.
The application of the radio and the calculator meant that at the end of the day, most of the work was complete. The surveyor could actually see the map as it grew day by day. Any holes were easy to pick up.. In fact, when I saw one I was usually able to call the field crew on the radio and get them to cover a missed area or get more shots in a tricky area before they came in for the day. What a cosmic difference!!
Since then, technology has advanced to the point where it is almost like science-fiction. Lasers for measuring distance, for God’s sake! In those days the laser hadn’t even been invented. Nor had the personal computer. Most of what we did in those days is unnecessary now. It wouldn’t even surprise me to hear that the whole process was now done by GPS or look-down radar or something equally arcane. The guys producing the maps now probably don’t go outside enough for a tan. And they probably don’t get the girls, either.
Posted by: swampy | 06-30-2008 | 11:06 PM
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