Dig Diary – Tuesday, August 23, 2016
Post-ex during the dig . . .
One of the most popular members of the Ness team is Bryn the site dog. A handsome Border Collie, Bryn regularly patrols the site and is an absolute pushover for a pat or an ear rub. He is also, we have to say, a first-class digger.
One of his important tasks is the welcoming of visitors to the site and he does this with huge enthusiasm and the waggiest of waggy tails.
You’ll have got the point by now… everyone loves Bryn.
But his latest tourist-related escapade left us gasping.
He made instant and fast friends with one of our American visitors who was clearly impressed by the site, but even more impressed by the dog.
The visitor sought our Bryn’s junior partner (Nick, the site director) and presented him with a donation of £100 which he made clear was because of the dog as much as the magnificence of the site.
Following on from this, there is now a strong move for Bryn to be named site director. It is felt that the judicious award of a couple of dog biscuits would lengthen the diggers’ breaks by ten minutes at least. (Ah well, we can dream).
Elsewhere today there is a palpable gloomy feeling associated with the imminent end of the excavation for this year.
The end is nigh, you might say.
There is, however, considerable work still to be done and Mark and Alette were busy scanning Structure 26 and Trench X.
More good news on that front is that Hugo’s latest 3D models of Trench T and Structure Fourteen are now online and will be posted following today’s diary.
The extraordinary, and so far mysterious, building at the Bottom of Trench T has been picked up by the wider media and has featured on the BBC, in the Daily Mail, the Herald and in a host of American magazines and internet sites.
Whenever this happens we have an almost instant spike of interest in the Ness and we fully expect that to happen again. Unfortunately, tomorrow, Wednesday, is the last day for site tours.
One of the tasks we work on in the ten months when we are not digging is post-excavation.
Broadly speaking, this involves assessing and dealing with the vast amount of data gathered during the two months of excavation and also with the many artefacts which have been found.
Unusually this year, we have been engaged in post-ex during the excavation because of our Spanish intern, Olga, a pottery specialist from Catalonia.
She has been working through part of the backlog of pottery and has discovered our first example of pottery with the impression of basketry on its surface.
It is an unusual type of impression, not being conventional ancient basketry but perhaps more likely to be organic material (grass, heather or straw) bound together in lengths with cord and then tied into a bowl or basket shape.
It has been carefully photographed by Ola and we will send his images for expert assessment.
Congratulations now to the winners of the Susan McGrath Ness of Brodgar/UHI Bursary Award for this year.
They are Holly Young, Charlotte Hunter, Simon Gray, Michael Ferguson and Emma Smith.
Well done, all, and the very best wishes to those of you who are heading off now for jobs in archaeology on completion of your University of the Highlands and Islands Archaeology Institute studies.
We’ll be back tomorrow, for the last diary of the season.
From the Trenches
My name is Mark Littlewood and I am the Geomatics Officer here at the Archaeology Institute, Orkney College University of the Highlands and Islands.
I deal with all the zappery out here and, yes, I am using that word. For the second year running, I am on site with most of the Archaeology Institute’s survey equipment bringing order and grumpiness to a busy archaeological site.
My apologies for the fair amount of acronyms that you will encounter in this blog; archaeologists tend to be worse than NASA and I actually know their acronyms!
For those of you who wonder what geomatics is or a geometrician (fun fact: real word!), basically we create maps on computers. You too can learn this skill, once upon a time I too used to be a full time field archaeologist.
For those people who say they are not technically minded and would never be good at it the chances are that the reverse is true; I have taught a fair few disbelieving people in my time.
And just because I’ve got your attention this is the bit where I say that I am also a maritime archaeologist and naval historian; I specialised in Chinese junks at university. So naturally I ended up in Orkney!
I am also fairly well versed in the naval history of World Wars One and Two. Recently I have had the unique opportunity of examining the Remotely Operated Vehicle (ROV) footage from the wreck of the 1st class armoured cruiser HMS Hampshire World War One war grave.
At the site I meet up with Sith Apprentice Alette Blom. Survey batteries are taken off charge, survey equipment is cleaned if necessary and maybe we get a chance to process yesterday’s survey data; if there are no urgent survey tasks to undertake. At the very least we back up the data cards off the machines on our geomatics laptop which will enable us to process the survey data at our leisure even if a machine is busy.
Those aforementioned survey records are filed in the folder and new survey TST survey sheets are prepared for our survey work at Trench P; hence forth to be known as the Big Trench.
These sheets are where we write done what items have been surveyed; Small Finds, Environmental Samples, Drawing Points, with their individual numbers and any necessary comments; did we change the height of the Detail Pole (I’ll explain what this is in a bit), could that point have been recorded in a previous year but has just lost its tick on the tag?
And then, finally, we get out on to site with the Total Station Theodolite (TST), a Leica Geosystem TCR1205
R400; which I have called Romana as naming machines is a bit of a geomatics tradition!
Basically it has a range of 400 metres and the R bit of the TCR means that we can toggle to a different laser and zap structures, the ReflectorLess (RL) laser. Our usual method uses the IR (InfraRed) which measures from the telescope of the Total Station to a reflector Circular Prism on top of our Detail Pole (see I did say that I would explain it). As the TST knows where it is, how high it is, how high the prism is on the Detail Pole and has just measured at a known angle, we can quickly establish the exact 3D coordinates of anything that we survey.
Fortunately, we don’t have do to these trigonometry calculations in our head and the speed of light or our laser zappy does not vary that much! And no, alas none of our lasers on the TST come in Death Ray mode!
And then it is on to surveying, well whatever is coming up that day; Small Finds, Environmental Samples, Drawing Points. Sometimes some items are more urgent than others, although Alette and I try to keep everyone in a sensible order depending on these priorities; after all we only have one Romana!
Sometimes you will see us trying to stakeout new grid points for people to draw their site plans off of. You’ll know when we are doing this. Apart from Alette telling me to go x centimetres to left, right, forward or back you will notice that I will be carrying a flag in my hand ready to mark the staked out grid point. I am usually on the Detail Pole side whilst shouting out numbers to Alette at Romana. We have tried the walky talkies this year, they are proving to be a bit…crackly.
Over on Trench T they use our Leica Viva GNSS (which I have called Nyssa, people may start to see a pattern now), our (roughly) centimetre accurate GPS. O.K. it also uses the Russian Glonass satellite constellation hence why we actually call it a Global Navigation Satellite System.
All GNSS machines talk to the satellites overhead, from which they receive signals. Hopefully you’re surrounded by satellite signals and they’re boxing you in on all sides. Think of it like big, invisible arrows pushing against you. If one pushes you from the front, then you’ll need a measurement from behind. O.K. now you’re being pushed off to the left or right, you’ll be needing big, measuring arrows coming in from the left and right to push you back into the middle.
However, GNSS are not 100% accurate; weather, obstacles like trees or buildings, satellite positional inaccuracies can all affect your measurement, basically those measuring arrows will arrive late and slightly longer than they should actually be! So how does Nyssa achieve its 1.5-ish centimetres accuracy?
Basically its talks via a modem to a stationary GNSS machine which (fun fact!) you may just be able to see this beacon outside Kirkwall Airport; it’s the Leica labelled dome in the area to the right of the terminal building. This machine is taking measurements from other satellites. So that machine at Kirkwall airport will effectively work out an inaccurate position, just like Nyssa, in the order of a couple of metres usually. Fortunately, it has been told where it should be and as long as nobody has decided to move the dome without asking it should then be able to correct its own position and then tell our GNSS where it is. Well, hopefully that sort of keeps it straight forward for you!
If you don’t see us out on site, it will probably be because the work has slowed down and we have time to process the previous day’s survey data from both machines and check the survey records. This involves creating data for use in various software formats; CSVs (Comma Separated Values otherwise known as spreadsheets), shapefiles for use in Geographic Information Systems (maps with data attached!) and yes the name does give a fairly clear idea of what these files should do and Computer Aided Design (CAD) drawings.
Nobody should be able to complain that they do not have data in an appropriate format! The methodology is the same for everyone, survey set-up, survey and survey processing all the way through to GIS and CAD should be the same for everyone. Just like filling out context sheets this is not the place to go free form, somebody else may have to make sense of your processed survey data!
Our other machine out on site is the Leica ScanStation C10, a high definition terrestrial laser scanner, called Astrid (O.K. I break the pattern here, try and guess which movie this come from; hint it’s animated). Henceforth to be also revered to as the mega zappy, capable of up to 50,000 points per second with a maximum range (onto white) of 300 metres and a usual effective range of 180 metres.
So what is a mega zappy, I mean laser scanner. Well as hinted above it will use a laser, again not a death ray, to accurate measure thousands of points per second. It will then use an on-board camera to colour up these points in real Red, Green, Blue values. This latter function can be useful, or occasionally frustrating. You can survey an area accurately. But if people then go back in when the camera is taking photos you will tend to end up with people coloured buildings! This is why we tend to clear people out of areas that we specifically want to laser scan.
Astrid is not always too keen on rain. Yes, she will scan the rain and you may have already seen some of these results from last year. I was particularly impressed by last year’s Rain Monster; we usually don’t get rain effects quite like that!
The resulting data from Astrid is a cloud of points, a pointcloud. That’s it, effectively, the software will have no idea what those points mean. So it is then up to a geometrician to draw any particular item from that pointcloud, the stones in the walls for example, either from the pointcloud directly of drawing off of a top down image exported out of the laser scanning processing software to use in either GIS or CAD.
And that’s usually our routine for the day; back-up, process (possibly), set up Romana and zap (or Astrid and mega zap) and then keep processing and zapping to keep on top of the data and the survey demands from the trowelling archaeologists. It can sound quite technical, but it’s quite interesting, possibly even a Spock-ian “Intriguing Captain” as the pattern of this year’s discoveries start to appear and populate the limits of our excavation trenches.
I tend to enjoy my time out at the Ness of Brodgar. It does take me away from my usual preference of naval history and maritime archaeology. This is probably the point where I say a McCoy-ism like “I’m a Naval Historian not a brick layer!”. But it’s surprisingly how much I still enjoy being out on site, getting back into all the old routines when I used to be a full time field archaeologist like everyone else and not stuck inside arguing with computers and printers.
And on that point I’d like to thank my Sith Apprentice, Alette Blom for putting up with all of my nonsense and to Romana, Nyssa and Astrid for behaving and going beep (or whirr in the case of Astrid) when required. See you out on site and maybe you too can create a people coloured scaffolding in a mega zapping!