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This is an aggregated collection of entries from archaeology blogs. The list is comprised of blogs from:

  • Past Horizons - written by Maggie and David (BAJR)
  • BAJR - written by David (BAJR)
  • ArchaeoGeek - written by Jo Cook, Information Systems Coordinator, Oxford Archaeology
  • Online Archaeology - written by Steve White
  • Theoretical Structural Archaeology - written by Geoff Carter

If you want to nominate a blog to be included in this aggregated list please get in touch.

Archaeology Blogs
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ArchaeoGeek
PgRouting and Mapserver

The third in an occasional series of posts dabbling in PgRouting

Once you’ve got your PgRouting database configured in PostgreSQL (see here and here for more information) you might want to use the routing data in an online map. There are a number of tutorials around for doing this using geoserver, and some information on using mapserver, but also a distressing number of posts pleading for assistance!

So, in the spirit of sharing, this is my attempt to pull the various bits of advice together into something a bit more comprehensive.

The key point to remember is that the PgRouting algorithms don’t return geometry, so you can’t automatically display them on a map. You need to join the query results to your network table to get your geometries and give you mappable results.

The most useful links about displaying routing data in mapserver are here and here, and you also need to know a little bit about mapserver runtime substitution, which you will find here.

The approach that worked for me was to take a working shortest_path query based on the examples given above, and test it in psql/pgadmin3. This gives you something like this (go back to my previous post to see the routing table structure for my Ordnance Survey ITN data):

select * from shortest_path('select uid as id, source, target, length as cost from  ways', 45, 65, false, false)

We need to join this to some geometry so we can use it in mapserver, so we alter it to this:

select wkb_geometry from ways join (select * from shortest_path('select uid as id, source, target, length as cost from  ways', 45, 65, false, false)) as route on ways.uid = route.edge_id

In this case, our source node is 45 and our target node is 65, but we want to be able to call these dynamically in our URL (This was the stage that seemed a little hard to find in the online instructions). Our mapserver layer needs to look like this:

LAYER
    CONNECTIONTYPE POSTGIS
    INCLUDE routingconnectiondetails.inc
    DATA "wkb_geometry from ways join (select * from shortest_path('select uid as id, source, target, length as cost from  ways', %source%, %target%, false, false)) as route on ways.uid = route.edge_id using unique uid using srid=27700'"
    METADATA
        "source_validation_pattern" "."
        "target_validation_pattern" "."
    END
    NAME "shortest_path"
    STATUS ON
    TYPE LINE
    UNITS METERS
    CLASS
        STYLE
            COLOR 255 0 0
            WIDTH 3
        END
    END
END

Note the layer-level metadata which tells mapserver to convert the parameters you give it in the URL into the parameters required in the data string.

We can then call this from the mapserver URL like this:

http://localhost/Mapserver/mapserv60?map=C:\iShareData\workshop\_MapserverConfig\routing.map
&mode=map
&source=45
&target=65
&layers=shortest_path

Which in my case returns something like: this

There are a couple of caveats here:

  • Firstly, in this very basic example, you need to know the ID of the source and target node, which is unlikely in a real-use scenario. You’d need to join your node data to some sort of alternative positioning data (Grid Reference, Address, etc) in order to use more intuitive start and end points, or allow people to click the map to generate them.

  • Secondly, you are calculating the routing on the fly each time the map is generated, which is fine with a small sample dataset but not so good in real life. Ideally you’d save the query results into a temporary table for re-use, but this is a good starting point.

22 Sep 2014
Theoretical Structural Archaeology
Dumbing down the past.
Dumbing down through abstraction
In two previous posts, [ 1 + 2 ] I have demonstrated that one of the central images of British Prehistory, the Wessex Roundhouse, is a construct which does not accurately the evidence.  It is not a discovery, or rocket science, I just read the relevant reports and looked at the plans and sections.
While I am happy to call these roundhouse constructs dumbing down, what to call the scholarship they generate presents a problem, since it represents the application of presumably perfectly acceptable theory to an imaginary data set. 
Archaeology is often at its best and most incisive when it has borrowed from other disciplines, but left to their own devices some academics have wandered off through the dewy system to delve into ideas about the relationship between people and built environments. But perhaps sometimes they just look at the pictures.
It is possible for anthropologists to study the relationship between people and their built environments; the humans can be questioned and observed, and the spaces inspected. In such a study, we might also wish consider factors of age, status, and gender, as well as more complex issues pertaining to the ownership and creation of spaces.
In anthropology, a theory, a set of ideas or a cosmology which explain the patterns of behaviour associated with particular places can be developed through the study of people and spaces. 
However, in Archaeology the people we study are dead and their spaces destroyed, or they usually are after we have finished with them.
If your understanding of a relationship is good enough, as in algebra, you can substitute one missing value, but not two; [? + ? = 4] is not a basis for understanding either of the unknowns.  In the study of prehistoric timber buildings there are no real people or spaces.  
Images from a Google 'Iron Age Roundhouse" image search. Note; only one image has anything to do with the Iron Age.
Archaeology is not a science, but more of a faith based study, and one reason for this is that people believe the pictures on the cover, but ignore the evidence inside, as is case with the roundhouse.  Further, since we have imagined and rebuilt the past, so it has seemed possible to sketch in one of the unknowns, and then project our theories into the minds of imaginary people who might inhabit in these pictures and constructs.
Hence, Iron Age Building Cosmology, or as my PhD tutor put it “… at least we understand roundhouses now…”.
Exemplum -
How people we have never met perceived spaces we have never seen - this was my terrible watershed moment, the retaliation there is no way through this mire of theoretical obfuscation. People take it seriously, it was an article of faith, and I was never going to be able to dumb my research down enough for PhD at Newcastle {caveat emptor}. It is not that understanding timber buildings is difficult, it just that it often conflicts with the pictures of the past and the ideas they generate. Unfortunately, as an archaeologist, I know that the picture on the cover is only a serving suggestion and not necessarily a guide to content, but;
  • The tutor knows she is correct about Iron Age Building Cosmology
  • Iron Age Building Cosmology is peer reviewed
  • The Postgraduate Dean knows the tutor is an expert in Iron Age Building Cosmology
  • The University knows there are no bad academics only poor students
  • All Institutions know there are no bad universities only poor students
The latter universal principle ensures that the application of simple engineering to archaeological evidence for structures remains a post – university study. 
The game is stacked against new research, I may have the numbers, but my tutor has the picture cards and can play a joker; you can't argue about the archaeology of timber structures with the Postgraduate dean, since, like my tutor, he also knows nothing about the subject, and has not read my work.  Ironically, you can’t have an academic argument with a university, since, in a faith based study, tenure infers a degree of infallibility; thus, in a faculty of arts, 3 + 1 can = 4, if you tutor says so. A faculty is only as smart as its dumbest don.
Realistically, Universities are fee earning institutions, there to look after the interests of their fee-earners, and as long as the fees come in, dumbing in direction is not a matter of concern.   However, dumbing down does appear inevitable as successive years of student intake have been perceived as poorly educated by academics who were themselves criticised by their own teachers.
Archaeology – The Trowel Test
As a result of the deep personal trauma of watchingmy life savings go down the pan because academics cannot distinguish between archaeological evidence and a construct of our shared visual culture, I am deeply suspicious of archaeology that has not been in contact with a trowel; a principle I extend to archaeologists.   Outside this redbrick reality, you cannot represent the views, opinions, feelings, perceptions, beliefs, cosmologies, or humour of the preliterate dead as some sort of knowledge, even if you use complex language and the magic words Claude Lévi-Strauss.
Most of what archaeology actually finds, things like postholes, can be summarised on a A4 context sheet, perhaps with a scale drawing on the back, and any bits of interest popped in a bag for later study; it’s simple, so simple even field archaeologists can understand it.  In contrast, the study of what archaeologists don’t find, and post-processualism in general, is characterised by irrelevant digressions into ethnography and theory, where simplistic observations are disguised by a complex, elusive, exclusive and intimidatory vocabulary, illustrating not only an inability to communicate, but also a lack of anything significance to say.  Dumbing down by abstraction.  
We need look no further than the Peter Principle, and what I imagine must be some form of Imposter Syndrome, as the cause of institutions that promote and protect a narrative of faith based learning.
 Circular Arguments
In the case of roundhouses, we connect their archaeology with buildings on the basis of shape, not form, function, construction method or materials.  Shape also trumps technology, culture, climate, and environment as a basis for comparison and ethnographic parallels. Above left; Little Woodbury reconstruction by  Crown Film Unit [2]
Except for a few notable exceptions, our pictures and realisation of the past are not real, or even necessarily evidence based, yet can have a powerful influence the way we think and visualise the past.   This visual conditioning presents the biggest barrier to understanding the evidence; it is probably akin to deprogramming former cult members, who have also received positive feedback and reward from their peers that reassures them their beliefs are rational, hoverer strange they may seem to us. 
Ploughing in Abyssinia - Johann Bernatz 1842 [3]
I have suggested that imperialism and classical education helped generate an idea of  ”primitive culture“ as a universal quasi-evolutionary phase somehow comparable to our Pre-Roman culture.  In addition, it’s natural that archaeologists, consider woodworking tools in terms the materials they are made from, rather than what they were used for, further aiding inappropriate comparison.  
I have also argued that, rather than copying his methodology, post-war field archaeology sought to reproduce the results of Bersu’s Little Woodbury [roundhouse] excavation, giving rise to a fundamental bias in our methodology and subsequent results[4]
  [Above; P Reynolds and J Lindsey ploughing at Butser ].
The untimely death of Peter Reynolds, leaving his work unfinished, has meant that what he had termed a "construct" has become slavishly reproduced as a "reconstruction". His original building at Butser had a roof pitch of 45˚, because he argued it is simple to create and it was used in Africa, which tells us much about an intellectual climate of his time, ideas that still persists today [5] .  The roof leaked and the structure was damaged in a storm and had to be demolished, which should have taught us more than it did.
This simplistic borrowed conception of a prehistoric built environment has created a discontinuity with our own historical architectural and craft culture, particularly the use of wood.   Dumbing down the past betrays its practitioners, patrons and the public, undermining value and trust in education among those who pay for it.  Experimental archaeologists, re-enactors, and the builders of ancient buildings want to believe in the authenticity and educational value of what they do.
Above left; Detail from Secoton North Carolina by John White, 1585.  [1]
As recent work at Stonehenge has shown, the representations of past landscapes that we have routinely imagined are completely wrong, proving basing our ideas on pictures and constructs is simply building a house of cards, sticks, straw, or any material you care to imagine.  

Sources and further reading
[1] Detail from Watercolour painted by John White, 1585.  "North carolina algonkin-dorf" by John White, explorer and artist - British Museum, London. Licensed under Public domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:North_carolina_algonkin-dorf.jpg#mediaviewer/File:North_carolina_algonkin-dorf.jpgJohn White (1585-1593)  http://en.wikipedia.org/wiki/John_White_(colonist_and_artist)
[2] http://www.screenonline.org.uk/film/id/469778/[3] Bernatz, Johann Martin (1802-1878);  Album of 19 drawings of scenes and landscapes made during an embassy to Abyssinia. 1841-1843
[4] G. Bersu: 1940: Excavations at Little Woodbury, Wiltshire. Part 1, the settlement revealed by excavation. Proceedings of the Prehistoric Society, 6, 30 -111
[5] Harding, D W, Blake I M, and Renolds P J, 1993 An Iron Age settlement in Dorsett: Excavation and reconstruction. University of Ediburgh. Department of Archaeology Monograph series No. 1. & visit http://www.butser.org.uk/index.html

13 Sep 2014
Past Horizons
British archaeologists fight with Italian farmer to save ancient aqueduct
In January father and son team Edward and Michael O’Neill discovered the headwaters of the aqueduct, which was built by the Emperor Trajan, hidden beneath a crumbling 13th century church north of Rome. A sophisticated example of Roman hydraulic engineering, the aqueduct, known as the Aqua Traiana, was inaugurated in 109AD and carried fresh water […]
06 Jun 2010
BAJR Blog
All change!
As you may have noticed, BAJR Blogging has remained unloved since December. This is because of the shiney new BAJR Federation site… http://www.bajrfed.co.uk get along there and enjoy…  with news, galleries and forum to keep you up to date and … Continue reading
09 Feb 2010
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