Accurate, precise measurement is a hallmark of land surveying. How it gets done is a combination of tradition and technology.
While attending a music festival in Scotland, my wife and I were moving between venues. We saw a road sign indicating a quarter mile to the place where the next performance would be and we decided to walk. When we got to the entrance, I commented to the Scotsman standing there guiding people that it was “a long quarter mile.” He replied, “It’s a Scottish mile.” We chuckled and began using the term Scottish mile to describe anything that seemed to be further than we had expected.
A few years later, I was reading Samuel Johnson’s Journey to the Western Islands of Scotland and came across a reference to a Scottish mile. Like anyone else these days, I jumped on the Internet to search out the facts. There are two versions, 1.12 or 1.42 statute (English) miles. The joke was on us because, at one time, we actually would have been walking further to cover one quarter of a Scottish mile.
That made me recall my early days at school where we had to learn about rods and chains and other forms of measurement we just knew we would never hear of again. After all, everything was feet and inches, with yards thrown in just to confuse us. Then we discovered the great deception. There’s another whole system of measurement – the metric system.
I like metric because it eliminates a lot of the confusion of fractions. Finding the center point of something where you have to locate the 1/32nd mark on the rule seems almost fruitless. The width of the pencil mark (definitely the saw blade) will render that moot. Meters, centimeters, and millimeters seem much more civilized. Let’s not get started on Fahrenheit and Celsius – 5/9ths?
Surveyors through the ages have not only worked under various systems of measurement, they have contributed to efforts to improve the accuracy of those systems. Mason and Dixon are best known for their work on the Maryland state boundary, but they also received a commission to provide an accurate measure of one degree of longitude.
When surveyors speak about “survey grade” measurement, it is not just a source of pride in the profession, it reflects an entire history. With lasers and GNSS systems providing ever greater accuracy, precise, repeatable measurement is possible without a lot of training. There’s clearly more to a surveyor’s job than measuring, but that’s another story.
Today’s tools would make short work of Mason and Dixon’s survey, relatively speaking. Remarkably, the accuracy of their “line” holds up pretty well when measured with modern tools. That said, it may be the significant gains in efficiency and productivity that are principal benefits of technology advances.
Manufacturers will continue to pour R&D money into improving accuracy of GNSS and other survey technologies. They will certainly also put effort into reducing the size and weight to make the units more field friendly and also make the tools faster. Faster is a real plus when you consider how much data is being collected during any given survey. Instead of big miles like the Scottish mile, we’re worried about big data. The solutions are already pouring onto the market, so stay tuned.
Meanwhile, I can’t help but wonder about an Australian mile. Given that a kangaroo can leap 30 feet, could that become a basis for measurement? “No worries, it’s only 30 Roos north of here.”