Playing with Ptolemy

Ever since I was an undergraduate (and attempted to write a “mental geography” of Roman Britain for my dissertation), I have been interested in Claudius Ptolemy’s Geography. Ptolemy was an Alexandrian Greek and his Geography dates to the mid second century AD: it contains coordinates from which it is possible to make maps of the entire known world at that time, including data representing the earliest surviving reasonably accurate survey of the British Isles. For the purposes of the EngLaId Atlas, that I am currently working on, I decided to see if I could plot Ptolemy’s Britain (or Albion as he called it) over the modern OS map.

To do so, I copied out the coordinates for Ptolemy’s places (representing points along coastlines, islands, and major settlements) from Rivet & Smith 1979. I suspect that there may be one or two typos in their lists (as a couple of the points in the final maps are not quite in the same place as they are on Rivet & Smith’s map), but I am not too worried about that for now. The task was then to convert Ptolemy’s coordinates so that they could be plotted onto the OS National Grid.

The first job was to correct for Ptolemy’s underestimate of the circumference of the planet (it was this underestimate that caused Columbus to be so confident about being able to reach the Indies by sailing west, thus accidentally discovering the Americas): to do so, all of the coordinates were first multiplied by 0.798. I then needed to recentre the coordinates so that they related to modern latitude / longitude: I used London / Londinium as a fixed point in both Ptolemy and the modern world, on the assumption that the provincial capital of Britannia ought to be relatively precisely located in Ptolemy’s data. This involved adding 8.41 degrees to each latitude measure and subtracting 16.06 degrees from each longitude measure.

I then created a shapefile in ArcGIS from the coordinate list using the WGS84 projection settings and then reprojected the  map into OSGB 1936, ArcGIS’s representation of the OS National Grid. The points were then filtered out into islands, settlements, and coastline vertices. I had given the coastline points an “order” field (based upon the order of coordinates in Ptolemy) and used the Points to Line tool in ArcGIS to convert them to a line. I then converted the line to a polygon using Feature to Polygon. Finally, a few extra vertices were added to the coastline polygon using the editing tools in order to ensure that the settlement points were all on dry land. Here is the result:

1_Ptolemy_draped

Several things jump out. The most noticeable (and long commented on) is Ptolemy’s rotation of Scotland. Why he did this has been the subject of much debate, possibly being due to him believing that a N-S Scotland would extend too far north or possibly being due to a lack of reliable data on travel times through those non-Imperial lands. The latter is rather key to understanding the Geography: whereas latitude was fairly straightforward to calculate in the past, without chronometers longitude was much more difficult and relied largely upon calculations made using travel time itineraries. We can see the results of this in the way that most of the settlements in England / Wales are reasonably precise in their latitude (N-S) but much more imprecise in their longitude (E-W): York forms a good example. Overall, considering the time when it was constructed, Ptolemy’s Geography contains an impressive representation of Britain (south of Scotland).

I then experimented with a couple of transformations to see if I could improve the plotting onto the National Grid. First, I tried rotating the data so that the north of England more closely aligned with the modern map (actually an affine transformation using London, York and Chester as fixed points, so the geometry is slightly deformed, especially for Scotland):

2_Ptolemy_rotated

The result is not really all that great, as the south of England then becomes much less closely aligned with the modern map. I also tried a rubbersheet transformation, using London as a fixed point and moving Ptolemy’s York onto modern York:

3_Ptolemy_morphed

This turns the map into a really quite close approximation of the modern English / Welsh coastline, with the exceptions of the immense length of the south west and the rather stunted East Anglia. However, as it disturbs the geometrical relationship between Ptolemy’s coordinates, I decided in the end that my first model was probably the best: after all, I could keep adding points to the transformation until everything mapped perfectly onto the modern geography, but what would be the point of that? I would just be recreating the OS map.

This was just a short experiment for the purposes of debate and making a nice map. It seems likely that I may have done something spatially naive in plotting the data using the WGS84 settings, but the end results are rather pleasing in any event.

Chris Green

References

Rivet, A.L.F. & C. Smith. 1979 The Place-names of Roman Britain. London: Batsford.

The maps contain Ordnance Survey data (OpenData). (C) Crown Copyright and Database Right 2016.

Field systems (IV)

This is another post about field systems, following up on my previous work on the subject (I)(II)(III). As stated in my last post on the subject, I now have a dataset of 40 field systems that I have digitised (based upon NMP data) and subjected to various analyses. Some initial results will be discussed below.

fsys_locations

all_fields_imbed

They range in enclosed area from around 2ha to over 1,100ha and cover time periods from the Bronze Age to the Roman period (with a single small section of early medieval reuse in one case). When plotted by time period, the earlier field systems are largely in the south of the country, whereas the Iron Age / Roman ones feature a more comprehensive national spread (the blue “PR” dots represent unspecified prehistoric or possibly Roman field systems):

fsys_period

When classified into rough categories of “coaxial” (meaning essentially rectilinear and perpendicular in character) and “aggregate” (meaning more amorphous), both types of field system occur across the country:

fsys_type

All of these field systems have been subjected to analysis of their morphology, topology (to a limited extent) and landscape character. Probably unsurprisingly, but usefully, field systems with less orientation “peaks” tend towards perpendicularity (y-axis is the difference in degrees between the centres of the first and second peaks on the orientation graphs, the x-axis is the number of peaks on the orientation graphs [5 peaks = 5+ peaks]):

27_fsys_peaks_vs_p1_p2_diff_degrees

Interestingly, the degree of “coaxialty” of each field system appears to have very little to do with how “open” the landscapes are, which suggests that the layout of field systems (particularly in the Bronze Age) did tend towards “terrain blindness” (x-axis is how “coaxial” each field system was from 0 [not at all] to 1 [very]; y-axis is how visually open the enclosed area of each field system is from 0 [very restricted intervisibility] to 1 [high degree of intervisibility]):

34_coaxiality_vs_visibility

One pattern that has emerged is a degree of bias in orientation towards a particular pair of approximate compass bearings around 100-120˚ and 10-30˚ (this graph shows the direction [and strength] of the two strongest orientation peaks from every field system):

16_fs_p1ANDp2

As the graph makes clear, this is not the case across the board, but it is common enough to suggest that there is something going on here. The orientation data was also plotted against the orientation of the aspect of the local terrain, to see if the latter could affect the former (red lines show aspect, black lines field system banks/ditches):

fsys_aspect_vs_coaxiality

As should hopefully be apparent, the aspect of the ground surface can influence the orientation of field systems (especially in the case of FS_id 25, which runs along the side of a fairly steep hill), but not in many cases.

Nationally, these data have been collated by 100x100km OS grid square, alongside orientation data for ridge and furrow, and for unstudied field systems via automated extraction of boundaries. Both of the latter datasets were based purely on the more modern CAD-based NMP projects and processed using automated methods, so the results are based upon more data than my set of field systems, but data that has been less rigorously filtered (numbers record the number of line segments analysed in each square):

coaxiality_by_100km_2

The ridge and furrow data shows a particularly interesting pattern here, with a very common bias towards perpendicular orientations just west of north and just north of east for areas north of the Humber. Hall has noticed this pattern before in Yorkshire, suggesting that it probably is the result of a planned reorganisation of the landscape on a large scale at some time before the C13th (2014:53), but my analysis suggests that this may have occurred over a very substantial area of northern England.

So, what we have here is people in prehistory and the Roman period constructing field systems that were sometimes very regular (“coaxial”) in character and sometimes less so, with the ground surface sometimes having an effect on the orientation and regularity of the field systems, but with field systems also often being laid out in a way that ignored the affordances provided by the ground surface. Often, these field systems were laid out on an orientation that pointed approximately towards a compass bearing of 100-120˚ (and at 180˚ to that, as these lines have no direction) and, to a lesser extent, towards approximately perpendicular alignments. When so-called “open field” systems were created from the later early medieval period, these also show an orientation bias (a different one), particularly north of the Humber.

I suppose that the natural inclination of archaeologists working in their respective time periods would be to find a more ritual explanation for the earlier phenomenon and a more pragmatic explanation for the later phenomenon. This in itself is problematic and one of the reasons why working across traditional time period boundaries (as we are) has the potential to produce new interpretations and understandings. For myself, I am not sure what I think (yet)…

Chris Green

References

Hall, D. 2014. The Open Fields of England. Oxford: OUP.

EngLaId conquers Paris!!

We are very proud of our project artist, Miranda Creswell, whose Paris exhibition in Le CentQuatre (sponsored by NEARCH) opened on 14 February.

The exhibition can be viewed until 30 April 2016.

Screen Shot 2016-02-22 at 16.40.39

For more information:

http://www.104.fr/programmation/evenement.html?evenement=519

(English-language information: http://www.104.fr/english/)

http://www.culture.fr/Actualites/Musee-Expos/Materialite-de-l-Invisible-L-archeologie-des-sens

French artist Nathalie Joffre also deserves a special mention, as her work was to a large degree inspired by a residency in Oxford, where she met and engaged with Oxford-based archaeologists on the Dorchester-on-Thames training excavations.

Finally, also see Tim Dowling’s column in this week’s Guardian – ‘the friend’s exhibition’ is, indeed, this very same event! http://www.theguardian.com/lifeandstyle/2016/feb/20/tim-dowling-valentines-day-paris

Field system orientation (III)

Following on from my previous work on field system orientation (I)(II), I have now finished data gathering for a set of 40 field systems across England, mostly within our case study areas, using data provided by Historic England’s National Mapping Programme. These cover almost 6,000 hectares and represent in part all of our time periods of interest (albeit there is only one early medieval example and even that is reuse of part of a larger prehistoric system). They should provide a decent set of evidence within which we can search for spatial and temporal patterns in prehistoric and Roman field system morphology.

I have gathered a whole series of metrics on these field systems (including dating evidence, length of boundaries, count of boundaries, etc.), which will be drawn upon in our later analyses, but I have started by thinking through orientation further. The set of graphs in the image below show the approximate orientation of field boundaries within each of our 40 field systems. The graphs require a little explanation. They each vary from 0 to 179˚ on the OS National Grid: this means that any axis through the centre of the graph represents 90˚ not 180˚. The black line shows the total length of boundary lines for each degree (relative to the bearing of greatest total length). Each line has been smoothed in order to bring out trends rather than showing the full complexity of the field system.

As such, symmetry along any axis on the graph can be seen as representing a stronger degree of “coaxiality”, as 180˚ on the graph represents 90˚ on the ground. Tighter peaks (so long as there are only two and they fall opposite each other) also represent a stronger degree of “coaxiality”. This provides us with a simple visual aid for assessing how “coaxial” or “rectilinear” a field system is and how each compares to other field systems. In this case, by “coaxial” I mean field systems where the boundaries tend to be orientated along two alignments perpendicular to one another.

all_fields

The variation seen remains to be analysed, to see if there are patterns across time and space, but some tentative initial conclusions can be drawn:

  • Many field systems show strong perpendicular symmetry. This is often also the case with those that did not appear particularly “coaxial” in plan form.
  • Some field systems show no favouritism towards particular alignments, although even these often avoid certain alignments.
  • Currently, there appears to be a bias across the dataset as a whole towards a particular coaxial alignment approximately targeted on NNE/ESE, although this needs further investigation to see if this represents a strong bias in one particular time period or spatial area.

However, we have yet to explore this dataset in its fullest detail, so further work is needed. I will try to report on any interesting patterns seen here in the future.

Chris Green

Past landscapes and communities: EngLaId conference, Sept. 2015

On 23 and 24 September 2015, the EngLaId conference ‘Past Landscapes and Communities’ took place at Keble College, Oxford. Researchers from 7 different European countries attended this two-day event, including specialists in later prehistoric, Roman and early medieval archaeology and history as well as GIS and landscape archaeology. This two-day event was structured around the broad themes of ‘identity’, ‘community’ and ‘landscape’, focusing on specific questions such as:

  • How can we model and visualize the use and history of landscapes in the past using multiple/large datasets?
  • How do material culture, spatial distribution, and landscape lead us to understand past identities?
  • Can we explore community identities and histories in the long term (and across disciplinary period boundaries)?
  • How does the situation in England compare to other regions within Europe?

A twitter feed was maintained for the duration of the entire event by the EngLaId team (see http://storify.com/EngLaID_Oxford/past-landscapes-and-communities). In what follows, the conference highlights are summarised on the basis of a series of photographs taken by EngLaId project artist, Miranda Creswell. At the outset, thanks very much to all participants, speakers, chairs, as well as a HUGE thank you to EngLaId’s Laura Morley for organising a seamless event!

Conference delegates enjoying the sunshine outside the lecture theatre

Conference delegates enjoying the sunshine in the picturesque setting of Keble College

Day 1: Wednesday 23 September 2015

At 9 am on Wednesday, EngLaId project PI Chris Gosden started the day off with the bold statement that he has definitively solved the concept of ‘identity’.

Chris Gosden's 'identity-formula'

Chris Gosden’s ‘identity-formula’

This was followed by the first ‘proper’ session of the day, expertly chaired by David Fontijn (Universiteit Leiden, Netherlands).

The first talk was by Alex Smith from the University of Reading, summarising some of the key findings of the Roman Rural Settlement project in his talk Identity in rural Roman Britain. Some of the results of this excellent Big Data project, bringing together rural settlement data from developer-funded excavations with a focus on portable material culture and agricultural practices, are now available on-line at http://archaeologydataservice.ac.uk/archives/view/romangl/.

Alex Smith discussing Roman cows

Alex Smith discussing Roman cows

The first session of the day was concluded by Mads Holst of Aarhus Universitet (Denmark) in a stimulating and beautifully presented talk entitled Collective manifestations in a herding landscape, which focused on agricultural regimes, the impact of barrow construction and settlement patterns in the later prehistoric landscapes of Jutland.

Mads Holst presenting his paper; David Fontijn chairing

Mads Holst presenting his paper; David Fontijn as chair

After a short coffee break, the day resumed with a three-paper session focusing on GIS methodologies, chaired by Roger Thomas of Historic England.

Mark Gillings from the University of Leicester kicked off with a fascinating talk about the little standing stones (and they really are _very_ little) from Exmoor, SW England, exploring the concept of Geosophical Information Systems in his talk Now you see me, now you don’t? Mapping the fugitive & invisible. Extensive processing time led to some interesting invisibility-viewsheds and the conclusion that we need to reconsider the significance of these stone arrangements.

Mark Gillings describing the _very_ little standing stones on Exmoor

Mark Gillings describing the _very_ little standing stones on Exmoor

After this, team EngLaId presented again, this time a double-act from GIS expert Chris Green and DPhil candidate Victoria Donnelly, entitled Embrace the chaos: structuring affordances and the PPG16 Big Bang. This drew together some of the highlights of their important research into the factors affecting archaeological patterning, such as archaeological investigation patterns and other ‘affordances’ (see previous blogs here and here for Dr Green’s discussion of the concept of ‘affordance’ in this context).

Chris Green and Victoria Donnelly, team EngLaId

Chris Green and Victoria Donnelly, team EngLaId

The final paper in this session was presented by Philip Verhagen from the Vrije Universiteit Amsterdam (Netherlands), presenting joint research with French colleagues Laure Nunninger & Frédérique Bertoncello. His talk was entitled From static distribution maps to dynamic models of occupation: rethinking spatial analysis of Roman rural settlement in France & the Netherlands, and compared different regions in France and the southern Netherlands.

Philip Verhagen in the flow of his presentation on dynamic settlement models in the Netherlands and France

Philip Verhagen in the flow of his presentation on dynamic settlement models in the Netherlands and France

From left to right: Mark Gillings, Victoria Donnelly, Chris Green, Philip Verhagen and Roger Thomas. In the background: Philip's suggestions for further reading on the subject matter of his excellent talk.

Discussion time. From left to right: Mark Gillings, Victoria Donnelly, Chris Green, Philip Verhagen and Roger Thomas

The discussion that followed made it very clear that this was going to be an excellent if exhausting two days (readily admitted by some of the attendees on the twitter feed!), and we retired for a well-deserved spot of lunch in Keble’s impressively huge dining room.

Keble Hall - apparently deliberately designed to be some 10 m longer than Christ Church College Hall..

Keble Hall – apparently deliberately designed to be c. 10 m longer than Christ Church College Hall.. (photograh by Victoria Donnelly)

After lunch, we entered the historical period with a stimulating talk by Grenville Astill from the University of Reading, who questioned existing assumptions about village nucleation and the development of England’s open field system in his talk Medieval fields, farming and villages – the basis of a communal English identity? Taking the bull by the horns, Grenville questioned whether a typical ‘English’ rural identity, focused on the village community, already existed prior to the 12th century AD, or whether the preceding period should be understood as a succession of different identities that eventually crystallised into a more familiar ‘village’ identity. Emphasising the importance of agricultural activity as the basis of human society, Grenville also drew attention to the high number of medieval documented murders that took place in fields in the context of day to day agricultural practices.

Grenvilla Astill on medieval villages and fields

Grenville Astill on medieval villages and fields

This session, which was chaired by Helena Hamerow of the University of Oxford, was followed by Alexandra Chavarría of the Università di Padova (Italy) who, on behalf of herself and Gian Pietro Brogiolo, discussed several impressive large-scale landscape projects carried out in the Colli Eugeni region in northern Italy (see http://www.memolaproject.eu/).

Alexandra Chavarría in the flow of her presentation, with David Fontijn, session chair Helena Hamerow and Chris Gosden on the front row in full attention

Alexandra Chavarría in the flow of her presentation, with David Fontijn, session chair Helena Hamerow, Chris Gosden and Alex Smith on the front row in full attention

Alexandra Chavarría and Grenville Astill during the discussion time

Alexandra Chavarría and Grenville Astill during the discussion time

The final session of the day was chaired by Mark Pollard of the University of Oxford. The first paper was a double act by Johanna Hilpert and Karl Peter Wendt of the Universität zu Köln (Germany), who presented their research (together with Andreas Zimmermann) on modelling population densities in the long term in their paper Patterns of demographic change and land use in sedentary societies.

Johanna Hilpert

Johanna Hilpert locating the study area

Karl Peter Wendt discussing their research

Karl Peter Wendt discussing their research

This was followed by another German talk, entitled Feeding from dense & sparsely populated surroundings – aspects of Early Iron Age communities in southern Germany. In this excellent presentation, Axel Posluschny of the Deutsches Archäologisches Institut talked about his research reconstructing Iron Age hinterlands around so-called Princely Sites (rather spectacular high-status burials) in the south of Germany.

Axel Posluschny debating

Axel Posluschny explaining GIS technologies to reconstruct hinterlands

The session was concluded by EngLaId DPhils Sarah Mallet and Dan Stansbie, who gave an excellent double talk on their research into food. Their talk, entitled Diet and regionality: the case of the (southern) English landscape 1500 BC – AD 1086, drew together some highlights of their doctoral research into animal bone, pottery and stable isotopes as a way to understand changing food practices in England from later prehistory to the early medieval period.

Dan Stansbie and Sarah Mallet introducing their research

Dan Stansbie and Sarah Mallet introducing their research

Saeah M

Sarah Mallet explaining the possible reasons behind some unusually high results from the nitrogen analysis

Dan Stansbie, Karl Peter Wendt and Sarah Mallet during the discussion

Dan Stansbie, Karl Peter Wendt and Sarah Mallet during the discussion

Although it was late in the day, the discussion that followed was animated, with some critical questions posed (and answered!). A few well-deserved drinks in the Lamb and Flag and a nice conference meal in Keble Hall concluded day 1 of this conference.

Day 2: Thursday 24 September 2015

The second day started off with a session on prehistoric landscapes and time in England and the Netherlands, chaired by Sarah Semple of Durham University. The first talk of the day was given by Harry Fokkens of the Universiteit Leiden (Netherlands). In his talk Searching for the past in the present, Harry charted the passage of time in some complex and well-preserved prehistoric settlement evidence that emerged around a Bronze Age barrow in West Frisia (the Netherlands).

Harry Fokkens discussing complex settlement patterns in West Frisia

Harry Fokkens discussing complex settlement patterns in West Frisia

The focus on barrows was continued in the talk by EngLaId’s prehistoric specialist Anwen Cooper, who presented her work on barrow relationships/histories/legacies in her presentation English landscapes from the perspective of Bronze Age barrows, 1500 BC – AD 1086. Some interesting visualisations were showcased, resulting from Anwen’s close collaborations with project colleague Chris Green, allowing for a more productive method of visualising and analysing the various spatial and temporal associations between Bronze Age barrows and other archaeological features.

Anwen

Anwen Cooper showing an interesting graph of the rhythm or tempo of different activities taking place at barrows in the East of England through time

Anwen

Anwen Cooper exlaining an innovative visualisation of barrow relationships (to be made available through the EngLaId website)

Anwen Cooper, Harry Fokkens and Sarah Semple at question time

Anwen Cooper, Harry Fokkens and Sarah Semple at question time

After yet another stimulating discussion and a much-needed coffee break, the day continued with a well-structured session focusing on different aspects of community from prehistory to the 11th century AD, chaired by Richard Bradley of the University of Reading. The first speaker of the day was Melanie Giles from the University of Manchester, who presented her work on the Iron Age ladder settlements of East Yorkshire in her talk entitled Making communities; interpreting the late Iron Age ladder settlements of East Yorkshire. Melanie emphasised the practice-based aspects of landscape, and gave the subject matter a very human face by reminding us of the micro-politics of everyday human interactions, including issues of conflict similar to those Grenville Astill had mentioned the previous day.

Melanie Giles in the flow of her presentation

Melanie Giles in the flow of her presentation

After this, it was back to team EngLaId with a presentation by early medievalist Letty ten Harkel entitled Enclosing space: defining boundaries in England c.1500 BC – AD 1086. Continuing the focus on practice, the aim of this paper was to suggest a holistic and interdisciplinary approach to the concept of enclosure, demonstrating the limitations of relying too heavily on archaeological evidence alone and emphasising the importance of the natural environment as a structuring element.

Letty ten Harkel discussing some graphs

Letty ten Harkel discussing some graphs

Letty finished her talk with an experiment to map the mass of EngLaId data against the hundred boundaries digitised by Stuart Brookes of University College London in a recent project reconstructing the administrative landscape of later Anglo-Saxon England (http://www.ucl.ac.uk/archaeology/research/projects/assembly). Stuart’s talk Polity & locality: unpicking the hundredal geography of Anglo-Saxon England followed seamlessly with a discussion of the data for these various later early medieval territorial divisions, showing the complex interplay between imposed and more organically developed administrative structures in the English landscape.

Stuart Brookes discussing later Anglo-Saxon England's hundredal geography

Stuart Brookes discussing later Anglo-Saxon England’s hundredal geography

At discussion time, the important question was raised whether spatial proximity implies ‘continuity’ or not, reinforcing a point made earlier during the conference, that we tend to understand ‘space’ much better than ‘time’. Much thinking remains to be done in this respect!

From left to right: Melanie Giles, Letty ten Harkel, Stuart Brookes and Richard Bradley during discussion time

From left to right: Melanie Giles, Letty ten Harkel, Stuart Brookes and Richard Bradley during discussion time

The final part of the day started off with a Spanish session, chaired by Gary Lock of the University of Oxford. Moving a little bit outside of the box, Felipe Criado Boado of the Institute of Heritage Sciences, CSIC (Spain) talked about Archaeologiques of space: linking landscape, materiality, perception and social domination (4000-0 BC).
Showcasing some innovative research about the way in which we look at things, Felipe’s discussion was impressively broad-ranging, covering everything from contemporary fashion to prehistoric pottery.

Felipe C

Felipe Criado Boado explaining the sight experiments carried out on test subjects using different images of prehistoric pots

The second paper in this session was presented by Julio Escalona of the Instituto de Historia, CSIC (Spain). His presentation Not quite the same: settlement and community in early medieval Castile analysed the complex interplay between different local and supra-local communities in early medieval Spain, exploring the concept of Dense Local Knowledge (DLK) as a way to understand community structure.

Julio Escalona presenting his research

Julio Escalona presenting his research

Gary Lock leading question time after Julio Escalona's paper

Gary Lock leading question time after Julio Escalona’s paper

The final session of the day was chaired by Zena Kamash of Royal Holloway University (previously EngLaId’s Roman specialist). The first presenter was Dagmar Dreslerová of the Akademie věd České republiky (Czech Republic) who gave a brief overview of landscape archaeology in the Czech Republic, and presented her excellent research (together with Peter Demján) into creating a comprehensive archaeological model for Bohemia, the western half of the Czech Republic.

Dagmar Dreslerová

Dagmar Dreslerová showing the model

The final talk of the day was given by EngLaId’s Roman specialist Tyler Franconi. His talk on Hydrological influence on floodplain settlement in Roman Britain and Germany brough us back to the Roman period, comparing the two river basins of the Thames and the Rhine and the interaction between human and environmental factors.

Tyler Franconi presenting his research

Tyler Franconi presenting his research

Zena Kamash posing questions of Tyler Franconi during discussion time

Zena Kamash posing questions of Tyler Franconi during discussion time

Dagmar Dreslerová and Tyler Franconi during the final questions

Dagmar Dreslerová and Tyler Franconi during the final questions

The day ended with a final discussion by Chris Gosden. Chris admitted that summing up the enormous breadth of ideas and subjects that had been covered was extremely hard, but managed to identify some common ground. Although the papers had traversed different scales, regions and chronologies, the subject matter of pretty much all of them evolved around the relationship between people and the land, emphasising the multi-faceted character of communities.

Chris Gosden summing up

Chris Gosden summing up

The ensuing discussion brought up many points that the EngLaId team will have to think about in the following year during the preparation of the monograph and other project output. These include the interplay between sharp discontinuities and overall broad continuities; the difficulty of understanding ‘time’; the benefits but also challenges of interdisciplinarity; and the problem of scale.

The final discussion

The final discussion

For updates on how our thoughts develop in this respect, watch this space!

Pondering regionality

I have recently been pondering the definition of regions, in the sense of carving England (or any country) up into contiguous zones of particular archaeological character. I would suppose that as a method of archaeological enquiry, this probably goes back at least as far as Fox’s division of Britain into “lowland” and “upland” zones along a dividing line running approximately from Dorset to Yorkshire. As a modern practice, I would suggest that recent interest in defining regions probably arises, at least in part, from the influential work of Roberts and Wrathmell (2000).

The reason why I have especially been thinking about this subject of late is due to the way in which two projects contemporary to our own have gone about structuring their reporting of their results. Their final report currently in press (Rippon et al. 2015), the Fields of Britannia (FoB) project divided the country (in this case being England and Wales) up into a series of regions (made up of groups of bio-geographical pays”). Similarly, the Roman Rural Settlement Project (RRSP) has also divided the country up into their own set of regions based upon the archaeological character of the excavated evidence found within each. Both of these projects based their regions around conglomerations of Natural England’s “Natural Areas“.

1 regions

Regions defined by other projects

If we compare these various regions on a map against the “Settlement Provinces” defined by Roberts and Wrathmell (R&W), we can see that there are broad similarities but also substantial local differences between the various regions (and provinces) defined. Herein lies the major problem with projects defining their own regions for analysis and reporting: it makes cross-comparison between different projects’ results difficult. For example, the Chilterns and the Berkshire Downs both fall within the south east regions of R&W and FoB, but within RRSP’s central zone: as such, can their respective “central” zones truly be compared? The simplest solution to this would be defining regions based upon modern political boundaries or, say, 100x100km grid squares. However, such an approach would result in regions that are archaeologically and bio-geographically irrelevant, which is very far from ideal (and so not recommended here!).

More fundamentally perhaps, I am also not convinced that archaeological remains (and thus, by implication, past human culture) truly lacks variety across such continuous areas of space and changes according to such sharp boundaries. I am sure that all of the researchers involved would agree with me on that and there is no doubt that defining regions helps in formulating ideas / arguments and in reporting results. However, I just wonder if there is a better way to structure our space? Some degree of structure is necessary, or all would be chaos and incomprehensible, but could alternative structures be preferrable?

2 HiLo model

Another experimental model (HiLo)

As an experiment, I constructed a regional model for England, but one that did not result in continuous regions, but rather fractured zones spread across the whole country. This model was based upon a mixed classification of elevation and terrain ruggedness and resulted in three new zones: a coastal zone (which largely seems to accord with former wetland areas), a lowland zone, and a highland zone (which seems to capture every important range of hills in England). These zones can exist in pockets within one another: they are not contiguous. Although not (by design at least) archaeologically relevant, these zones certainly have a degree of bio-geographic meaning. Furthermore, they would be reproducible by other scholars, assuming I publicised their construction method. As a Warwickshire man, I am particularly taken with the result that my county almost looks like a “natural” division of the country!

3 regions vs HiLo

Other regions against HiLo

If we compare these three “HiLo” zones (named for Oxford’s infamous Jamaican inn) against the regions of the other projects we can again see some similarities between the borders of my zones and those of the other projects, but again with substantial local differences. Obviously, if we were to use my HiLo regions for reporting on our project, we would just end up compounding the problem of difficulty of comparison, but the experiment remains of interest.

elev_RandW

Elevation: Roberts and Wrathmell

elev_FoB

Elevation: Fields of Britannia

elev_RRSP

Elevation: Roman Rural Settlement Project

elev_HiLo

Elevation: HiLo

I then tested each set of regions against a series of other datasets: elevation, terrain ruggedness, broad soil types, soil wetness, etc. The graphs above show just the elevation results, but the broad conclusions were similar for all comparisons. Essentially, the FoB and RRSP regions look far more distinct than the R&W provinces. This is hardly surprising as they are of smaller spatial extent: the smaller a sample area, the more distinct from the general “population”/pattern a variable ought to tend to be. This is clearly the case here. However, the HiLo model sits somewhere in between. It only has three zones, but they appear far more clearly differentiated than the R&W provinces. As such, we can conclude that they have greater geographic differentiation, due to their non-contiguous nature, despite being of similarly large extent.

8 regions_thes_all

Regions: archaeological variation (area normalised)

9 regions_thes_pc_all

Regions: archaeological variation (percentage)

As a final test, I then compared each set of regions against our archaeological data, using our coarsest level of thesaurus categories. I did this for each broad time period, but the results shown above are for all EngLaID time periods combined (unspecified prehistoric, Bronze Age, Iron Age, Roman, early medieval). The conclusions, interestingly but perhaps not surprisingly, are very similar to those seen when comparing against the “natural” factors described just above. FoB and RRSP regions look fairly distinct, R&W rather homogeneous (albeit with less dense data in the north west), and HiLo regions are more distinct than R&W but less so than the others. Again, the size of regions remains key (due to the MAUP).

Since undertaking these comparative experiments, I have been reading a recent report by Historic England’s Andrew Lowerre (2015). In the second half of the report, Lowerre uses a mixture of environmental variables alongside Roberts and Wrathmell’s data to define regions using automated clustering techniques. The regions that he produced (across a series of different models), much like my HiLo model, are non-contiguous and possess fuzzy borders. As such, to me at least, they seem much more representative of the data than regions defined manually. I wonder if this type of automated region creation is the way forward if we wish to define regions for our analysis and reporting?

Regions are undoubtedly a useful and intuitive way to divide up space that makes analysis and reporting of results within the context of a project relatively simple and straightforward, both in terms of how a team thinks about their data and in terms of how an audience may digest the same. However, the cross-comparison issue is distinctly problematic when one begins to think beyond the bounds of the results of a single project. We could potentially define a set of regions based on the natural environment that all projects should attempt to use, but we as archaeologists often seem to be naturally inclined to always do our own thing, so I am not sure that would be fruitful. Plus the set of regions defined might not be relevant across multiple time periods.

As such, I do wonder if we ought to avoid the idea of archaeological character regions altogether and just talk about variation in data across space. So long as that data is quantifiable and mappable as continuous fields, then cross-comparison becomes simple: map overlay is after all the most obvious application and strength of GIS, with whole suites of tools and methods dedicated to it.

This post is not intended as a criticism of the methods of other projects, which have undoubtedly proved fruitful and interesting in each case. I just wanted to express why I feel we (as EngLaID) ought to avoid regions in our reporting, especially as a project looking across traditional period boundaries. Others might disagree, but I do feel the cross-comparison issue of bespoke regions is a thorny problem, particularly for those interested in broad syntheses across time and space.

Chris Green

References

Lowerre, A. 2015. Rural Settlement in England: Analysing Environmental Factors and Regional Variation in Historic Rural Settlement Organisation Using Regression and Clustering Technique. Portsmouth: English Heritage. http://research.historicengland.org.uk/redirect.aspx?id=6288

Rippon, S., C. Smart and B. Pears. 2015 (in press). The Fields of Britannia: Continuity and Change in the Late Roman and Early Medieval Landscape. Oxford: Oxford University Press.

Roberts, B. and S. Wrathmell. 2000. An Atlas of Rural Settlement in England. London: English Heritage.