Sunday 28 October 2012

Home Maintenance, Standing Stones and more Viewsheds







Friday: Noticeably cooler today. The home is like an open house - kitchen fitters, electrician, gas engineer and carpet assessor all booked in to make good things that aren't quite right! Aaahh! Home improvements!

So back to viewsheds.......and this time we will move to Pembrokeshire. I will use Google Earth again to explain things, so you will need to make sure you have this installed on your computer. It is a free download from:



As I mentioned a couple of posts ago, archaeologists often try to discover how inter-visible monuments are in the landscape as this helps in trying to understand any possible ritual role they may have had in the past. Standing Stones, those enigmatic totems from (mainly) the Bronze Age, have been subject to much spatial analysis in a bid to establish their possible ritual significance for those peoples that erected them.

Stonehenge is an example of an alignment that clearly attaches much importance to the mid-summer sunrise, and similar sight-lines exist at other prehistoric structures across the UK, and indeed across the world. Many of the stones of Stonehenge originated from Pembrokeshire, but how these "bluestones" travelled from the Preselis to Salisbury Plain still promotes heated discussion.. Man or nature? At the present the tide of opinion has flooded to the idea that prehistoric peoples transported them, (from now well identified outcrops),  for reasons best known to themselves.

To read alternative views  on the movement of the bluestones form Preseli to Stonehenge try:


or countless other online discussions.

Anyway, I digress - back to viewsheds and standing stones.

In South Pembrokeshire there are three standing stones in fairly close proximity to each other. They are all on what was the Stackpole Estate, and as is common with such things, there are folk tales associated with them. Firstly, let me introduce you to the dramatis  personae.

Devils Quoit (St Twynnells parish)

B - Harold Stone (Stackpole/St Petrox)

C - Devils Quoit (Stackpole)




The most enduring folk memory connected to the three stones is that at sunset on the summer solstice, they come to life and dance together at Sais Ford (a derelict cottage near Sampson Farm, at the site of a fording of  Treforce Lake), returning to their stations by dawn.

Here is a Google Earth file to show their locations, along with that of St Twynnells church


The viewshed of the Harold Stone is of particular interest. Today it has taken about 5 minutes to establish what the view from the Harold Stone is like. In the Bronze age, the ground might have been just as, if not more, open. The orientation of the Harold Stone is of interest too. It is a large slab of the local carboniferous limestone, like a large plate 30 cm thick. If you sit with your back against the plate, you are either facing north-west of south-east, depending upon which face you choose to rest against. facing south east, you are looking straight into the modern hedge. Without the hedge, the view is no more than 400 metres. You can check this on Google Earth using the ruler tool.

The view to the north-west is far more expansive.

In the mid-1980's my interest in megaliths had been ignited after a weekend's study school with Aubrey Burl (http://en.wikipedia.org/wiki/Aubrey_Burl) at Urchfont Manor near Devizes. I read widely about the archaeology of standing stones, henges and stone circles. I considered the ideas of Alfred Watkins, the great investigator of "ley lines" (http://en.wikipedia.org/wiki/Ley_line), and the intense archaeo-astronomical writings of the like of  Alexander Thom, who worked on the astronomical alignments of standing stones, believing that our ancient ancestors measured the motion of the sun, moon and stars with great precision. (http://en.wikipedia.org/wiki/Alexander_Thom)

St Twynnells church from the west
I eventually did what you might call today a "desk based assessment" of the alignments of the two Devils Quoits and the Harold Stone. Drawing lines carefully over my well used Castlemartin OS Pathfinder map. the obvious thought was whether any alignments matched up with the sun rise or sun set at the solstices. In the lounge of the Suffolk cottage I was renting at the time, with its huge open log fire, the alignment of the Harold Stone with the Devils Quoit in St Twynnells looked promising. A site visit in the early spring, saw me sitting with my back against the Harold Stone, looking north-west directly at the Devils Quoit, and in the far distance the slender limestone grey tower of St. Twynnells Church on the crest of the old red sandstone ridge. It was uncanny, the way in which sitting relaxed against the slab, your sight line fell on the two distant monuments, their ages separated by a few thousand years. Had I found a Ley Line? Wouldn't it be "so cool" if the sun actually set at mid-summer over the Devils Quoit and St Twynnells Church?



Looking east from the top of St Twynnells church tower
Over the next few weeks my interests focused on different things - the wills and inventories of those who had died in St Twynnells and and the neighbouring parish of Warren in the seventeenth and eighteenth centuries. I stopped thinking and reading about megaliths and the "Dancing Stones" of Stackpole - but not for long..........






By the way, the electrician didn't turn up, but the kitchen is now working properly, the damp problem was a false alarm and the damaged carpet will be replaced in time...



Next Time ....
 The things parents do for you, standing stones and the burial of William Poyer.



Thursday 25 October 2012

My Phone can now post!









After much guesswork, I can now make posts from my phone should I need to. That was a challenge!





View sheds, Mobile phones and Archaeology

I have a fascination for archaeology and the way we lived our lives in the past. I am also wedded to my mobile phone (Windows Omnia 7) and feel cast adrift if I am out of signal range.

We are all familiar with the network coverage diagrams on the websites of the mobile phone companies, which tell us with reasonable accuracy where we might expect our mobiles to work. These diagrams are produced by calculating the theoretical viewshed of each mobile phone transmission mast and plotting this on a map.

What do we mean by this?


Mobile phone signals travel in straight lines (there is some bending or refraction of signals by the atmosphere). Generally speaking, the signal will not penetrate through hills, but will pass through trees, vegetation and most buildings (although some attenuation or reduction does take place). To all intents and purposes, if you were to stand  at the top of a mobile phone mast, the terrain you could see from your perch would define the area where you might expect your mobile phone to work. This is the viewshed for this mast.There will be some valleys, or land hidden by hills that you would not be able to see, and in these hidden locations your mobile phone would not be able to communicate with the the mast and you would be out of signal range. Of course, the strength of the signal diminishes with distance from the mast and this also has an effect on reception.

There are several freely available software solutions for plotting the viewshed of a given mobile telephone mast. The one I use is web based at:

http://www.heywhatsthat.com/

This will plot a viewshed on Google Maps or you can export a kmx file to view the viewshed in Google Earth. The link below shows the viewshed for a mobile telephone mast at Pigeons Lane, to the west of Ipswich , Suffolk. You will need to have Google Earth installed on your computer to view this.

http://sdrv.ms/RXysFB

The use of viewshed calculations can be used for planning the area that a radio station might be able to cover from a given location. This would be particularly important when planning communication networks for an emergency relief operation or a military command post.

However, apart from carrying out analyses and planning for future requirements, viewshed software plays an important role in trying to understand the past. Archaeologists use such techniques to establish, for example, whether inter-visibility between monuments might have been important. The analysis of the viewshed can help us learn about why monuments and buildings might have been built in a given location.

The link below gives you the viewshed plot on Google Earth for Sutton Hoo, in Suffolk.

http://sdrv.ms/RXDNN1

Looking at the viewshed allows us to consider whether the visibility of the cemetery site was influential in it being selected for the burial of a Saxon king. For more information about Sutton Hoo, follow the links below:

The Sutton Hoo Society:
 http://www.suttonhoo.org/index.asp

The National Trust:
http://www.nationaltrust.org.uk/sutton-hoo/


The British Museum:

http://www.britishmuseum.org/explore/young_explorers/childrens_online_tours/sutton_hoo/sutton_hoo.aspx



More about viewsheds next time.


Time Team is Dead! Long Live Time Team!



Wednesday 24 October 2012

Camouflage and Colchester

Just returned from Colchester, main reason for the visit was to go to the bank, but obligatory visit to ASDA fitted in too!

By the District General Hospita (DGH) there is a fairly tall telecommunication mast, the lower part of which is dark grey and the upper part painted in broad white and red bands. Against the misty, milky autumn sky the white portions of the mast were largely invisible, and this reminded me of the tall tower cranes near The Hythe, down by the river.

Here there is one very tall crane that is painted white, and about half a mile away some more cranes painted red/orange. Again, the white crane, despite its height was far less obtrusive than the orange cranes. White is a good camouflage colour!

The idea that white is a good colour to use to disguise the shapes or visibility of objects seems counter intuitive (except in the snow!), but my thoughts about this were challenged when I recently read a book called "Ship Shape".

"Ship Shape - A Dazzle Camouflage Source Book" by Roy R. Behrens (2012) describes the development of this highly artistic form of the camoufleur's work.

http://www.bobolinkbooks.com/Camoupedia/DazzleCamouflage.html


The above link is to an excellent resource on the art and science of camouflage.

Below is a picture of a ship in dazzle camouflage, taken from an airship flying from the Royal Naval Air Station Pembroke in WWI.
A naval escort in dazzle camouflage.



Here we have a convoy, probably off the coat of Pembrokeshire, in WWI, some of the ships wear Dazzle camouflage.
A convoy off the Pembrokeshire coast c.1917

The camouflage was designed to be deceptive rather than concealing, supposedly making it harder for submarine captains to work out the speed and direction a ship might be sailing when viewed through a periscope.

To conceal a ship from view, trials showed that in the North Atlantic, against the usual pale grey sky, white paint was likely to be the most effective. The reasons for this are explained in "Ship Shape".

So, the next time you go for a walk by the seaside, observe the visibility of seagulls from sea/ground level. When are they less obvious? When do they stand out?

This is where the cranes in Colchester come in.....


I can recommend "Ship Shape".

Still Getting to Grips

Took ages to find this blog again so that I can add some more. Finding that my Picasa albums were suddenly public on Google+ was a bit of a surprise, but I think I have sorted that!

The time on Previews still seems to stay stubbornly on PDT.



Tuesday 23 October 2012

Starting Out

This is a first venture into the blogosphere, and I do wonder what I will talk about. I suspect that it will be a mixture of random thoughts and travels that will appear to have no form!

I will sometimes pose questions and if you should happen to know the answer, or can offer some hints to point the way, then it would be a delight to hear from you.

At the moment I do not have a clue what this is all about, so let us see what transpires. For example, I notice that the time on the preview of this post is 04:31. That cannot be, so... let's try and sort that out!

Aha! Post Settings, just to the right of where I type! I am looking for UTC or GMT, but seem to be getting PDT.