The reason I made this a multi and not a traditional is because my curiosity was piqued when I read that this modern survey marker was placed as close as possible to Evans' original survey line. Obviously factors like the railway, modern roads or houses would make an exact placement impossible, I first thought. The line of Evans' survey would naturally have stayed high, on top of the ridge where the road needed to be built, and as a natural route for Evans as he returned from his journey across the mountains.
As an experiment, I decided to give the coordinates on the survey marker a try, and found I ended up in an unexpected place. It led me to wonder about a few things.
First of all, having no experience in surveying or any of its associated fields, I began to wonder at the difficulty facing Evans, trying to make a survey of unknown territory with the tools of his time, like the circumferenter or log tables. And if you've ever bush bashed towards a cache with just your GPS in hand, you might begin to imagine what he was up against.
The circumferenter, pictured on Evan's survey marker and shown here, was a flat bar with sites at either end with a magnetic compass playing in between. This device was supported by a tripod and was used for measuring horizontal angles. The modern theodolite has now replaced it. This picture, taken from the survey marker, is a circumferenter, presumably of the type used by Evans.
So having followed Evans' coordinates, a few questions came to mind. For example, the problem of how close we can estimate Evans' survey line from his notes, (or, as an aside, the precise location of many historical markers and events. I was made aware of this late last year when I was in Victoria in the park of the Eureka Stockade. The stockade is known to have been somewhere in the vicinity of the park, but its precise location is not known. ) After all, the instruments Evans had to work with were far less accurate.
To highlight this problem, consider this comment on the Registrar General's website which states:
"... the boundaries of very early surveys, ... before 1870 were measured only by circumferenter and Gunters chain. Allowance for factors like sag, slope and temperature was made by overstating the measured distance. In this way the owners entitlement was assured. Accordingly, re-surveyed distances using modern equipment will, in general, be greater than the deed distances. By todays standards the measurement of both azimuth and distance was poor, however, some rural surveys (especially those relating to public roads) were of high standard."
To put this in perspective, I found a 'best practices' PowerPoint on Rural Cadastral Surveys designed for modern surveyors posted on the internet and dated 28th March 2008. That claimed that in the 6 years prior to that, nearly one quarter of all surveys failed in accuracy. As I said, you can imagine the problems that beset Evans with less accurate equipment while trying to traverse dense bush.
As GPS users we hope to get within a 3 metre radius of accuracy. When you go to look for this cache you may be frustrated by the inaccuracy of your GPS at GZ. That's why I gave a little hint. But how accurate did Evans hope to be? Obviously surveys made in the bush were compensated by common sense approaches, as shown by the Registrar General's comments. Yet I had to wonder when I reached the coordinates given on the survey marker whether they were merely general coordinates and that more accurate coordinates existed elsewhere. Or was this really an example of the problems faced by early surveys? Perhaps somebody who knows something about these things can let me know via their log.
[Since publishing this cache, Mr Darcy has offered some information about the questions I have raised which suggest Evans was more on the mark than I thought. You might want to Read Mr Darcy's Log, since he actually knows what he's talking about. You may also wish to visit the Geoscience Australia webpage, a link which Mr Darcy supplied, to read further. As for the rest of these cache notes, I have left them as they originally appeared, since they at least explain the questions that motivated me to place this cache.]
So for me this was a moment when I reflected upon the things we now take for granted: modern maps, satellites, modern roads and GPS. Perhaps you will also stop to consider how much things have changed, for a moment, as you sign the log book.
I suggest, out of interest, you also take time to read the information about Evans from the marker, as well as information on other plaques in the park, before you head off for the cache.
THE CACHE The cache is a small black Sistema container. While the beginning of your search may take you very close to private property, you do have a public right of way.