Integrating Types of Archaeological Data – Dan’s Major Project

Dan Joyce, our trench supervisor for the 2013 summer field season last year, has written a blog post to summarise his major dissertation project. Dan studied the University of Southampton Masters in Archaeological Computing last year, which he completed at the end of 2013 (well done Dan from the Basing House team!!!)! Dan’s project looked […]

Dan Joyce, our trench supervisor for the 2013 summer field season last year, has written a blog post to summarise his major dissertation project.

Dan studied the University of Southampton Masters in Archaeological Computing last year, which he completed at the end of 2013 (well done Dan from the Basing House team!!!)!

Dan’s project looked at how archaeologists can mesh together different types of archaeological data.  Dan is a graduate of the University of Southampton’s Masters in Archaeological Computing run by the Archaeological Computing Research Group.

The course has two major strands to it, one concentrates more on 3D graphics and the theory of archaeological visualisation (Gareth and I are also graduates from this programme), and the other on geographical information systems and survey.

Thanks to Dan for writing this post. 

CLICK ON AN IMAGE IN THIS ARTICLE TO SEE IT UP CLOSE.

Dissertation on the integration of digital archaeological data

Introduction

My dissertation for my masters in Archaeological Computing (Virtual pasts) at the University of Southampton was concerned with integrating different types of digital archaeological data from Basing House. This included a total station and GPS (Global positioning system) topographical survey of the site, a total station building survey of the 16th century manorial barn, lidar data of the site, geophysical survey data, total station and photogrammetry data and section drawings of the 2013 excavations as well as digital context information.

Topographical and building survey integration

As part of the practical aspect of the Advanced Archaeological Survey course undertaken at the University of Southampton a topographical survey was undertaken on the site using a total station and GPS to record points on the ground. These points were then processed in both the GIS (Geographic information system) software ArcMap and AutoCAD Civil to form a coherent surface. In the case of AutoCAD Civil a TIN (Triangulated Irregular Network) was created, this forms a surface by joining the points together to form triangles (figure 2). In ArcMap a raster DEM (Digital Elevation Model) was created, this forms a much smoother surface by interpolating the surface between the known points (figure 3).

A standing building survey was also undertaken on the 16th century manorial barn using a total station (figure 1).

Figure 1 – Total station building survey of manorial barn

The two surveys were combined, with the topographical survey and the building survey appearing together in their correct positions within the British National Grid reference system, as can be seen in figures 2 and 3.

Figure 2 – TIN of topographical survey with the building survey of manorial barn

Figure 3 – Raster of topographical survey with the building survey of manorial barn

Geophysical survey integration

As part of the practical aspect of the Archaeological Geophysics course at the university, a geophysical survey of much of the site was undertaken, this involved resistivity, magnetometry and ground penetrating radar surveys. The results from these surveys were integrated with that from the topographical survey within ArcMap as can be seen in figures 4 and 5.

Figure 4 – Resistivity survey overlain on top of TIN of topographical survey

Figure 5 – Magnetometry survey overlain on top of TIN of topographical survey

Another step was to integrate the lidar data procured of the site with GIS and the geophysical survey data as seen in figure 6.

Figure 6 – Geo-physical survey data overlain on top of lidar data of the old house

Lidar data

As we had procured lidar data of the site from the Environment Agency it was decided to experiment on it. A number of features could be seen in the lidar data of the common using a hillshade in ArcMap (or other software). A hillside creates an artificial light source within the software from a set direction and altitude causing shadows to be formed by any raised areas in the lidar data (figure 7); altering the direction and altitude of the light source can reveal different features. More on this can be seen in my blog on processing lidar data.

Figure 7 – Lidar data of the Common showing a number of interesting features

Some of these features can also be seen in the geophysical survey of the common undertaken by Clare Allen.

Figure 8 – Geo-physical survey of the common overlain on top of the lidar data

3D visualisation of existing archaeological data

As an aid to understanding the 1960s excavations before we began the 2013 excavations I digitised the plans and sections and created a 3D model in AutoCAD, although far from perfectly accurate the model made it much easier to understanding how features related to each other in this earlier dig and what was missing.

Figure 9 – 3D model created from 1960s excavation data

I experimented with a number of methods of tying the context information from these excavations to the sections, including just displaying it next to the section within AutoCAD.

Figure 10 – Digitised section with context information

A later attempt with the data from the 2013 excavations involved the entering of the context information from the excavation into an ARK database (a web accessible database solution created by L-P Archaeology), a hyperlink was created and linked to each context which referenced the relevant webpage associated with the data in the database and this data could then be displayed with one click of the relevant context within AutoCAD.

Figure 11 – Digitised section with ARK database record

Special find information could be displayed in the same manner by clicking on the relevant point in the model.

Photogrammetry

Photogrammetry is a technique where 3D models can be created from multiple overlapping photographs by matching the same point in each photograph. As well as using it to record the 2013 excavation I experimented with it to see if slides from the 1978-83 excavations could be used to create a 3D model of this dig. Although it was quite successful much more work needs to be done on the process including surveying in known points on site to aid with stitching the photographs together.

Figure 12 – Photogrammetry model of the old house gatehouse from the 1978-82 excavations

Photogrammetry was also undertaken on box 9A during the 2013 excavations to see how good a 3D model could be created (figure 13), four nails were driven in at the four corners of the box to act as ground control points.

Figure 13 – Photogrammetry model of Box 8A

Figure 13 shows Box 8A with the four ground control points which were surveyed in allowing the integration of the photogrammetry model with ArcMap as can be seen in figure 14 where the model is displayed in its correct position underneath the TIN created from the topographical survey.

Figure 14 – Integration of photogrammetry data with topographical survey within ArcMap

Experimentation was also conducted on recording the excavations from above using a camera attached to a 3m pole (figure 15).

Figure 15 – Elevated photography on a pole being undertaken

This technique allowed the creation of a 3D photogrammetry model of the whole excavation (figure 16).

Figure 16 – Photogrammetry model of the 2013 excavations

3D contexts

Due to the fact that the 2013 excavation was recorded with a total station by surveying the outline of contexts and taking levels on the top of them it was possible to experiment with the technique of creating 3D contexts within AutoCAD. First the points from the context were turned into TIN surface (figure 17).

Figure 17 – Wireframe surface created from total station survey of a context

Then the surface was extruded downwards (figure 18)., the same was done with the context below and the second 3D object was subtracted from the first to form a 3D context. This was continued until all the contexts had been created in 3D

Figure 18 – Wireframe 3D context

Due to the fact that few contexts were actually removed during the excavation part of one of the sections was chosen for this process resulting in the creation of a series of 3D contexts within AutoCAD which could be removed at will virtually recreating the excavation process (figure 19). The volume of the 3D context could also be calculated adding this information to that recorded during the excavation.

Figure 19 – Section of 3D contexts created from total station data

Integration of total station excavation data

Due to the fact that the excavation was recorded digitally using a total station it could easily be incorporated with the topographical survey and building survey data recorded previously. This can be seen in figure 20 where the surfaces created from the excavation data can be seen under the TIN created from the topographical survey in AutoCAD.

Figure 20 – Integration of excavation data with topographical survey in AutoCAD

While figure 21 shows the point data underneath a TIN surface in ArcMap which is unable to display the surfaces created n AutoCAD.

Figure 21 – Integration of excavation data with topographical survey within ArcMap

Conclusions

Although this work demonstrates the potential for the integration of many different types of digital archaeological data a great deal of work still needs to be done to make it a practical process and to solve a number of problems.

Blog post by Dan Joyce


Filed under: Dan Joyce, Data Processing, Digital Methods, Excavation Plans, Geophysical Survey, Images, Magnetometry Survey, Spring Survey, Summer Excavation Tagged: 3D, 3D context, Archaeological Computing, ArcMap, ARK, AutoCAD, barn, building survey, context, Environment Agency, excavation, gps, Lidar, MSc, photogrammetry, TIN, topographic, total station, wireframe

Interim Report 2013 – Geophysical Survey

This Interim Report will soon be available as a PDF on the Hampshire County Council website for Basing House. The authors are: David Allen Gareth Beale Nicole Beale Chris Elmer Jude Jones Kristian Strutt Clare Allen Daniel Jones There are three posts that make up this report. The post below describes the excavation and recording […]

This Interim Report will soon be available as a PDF on the Hampshire County Council website for Basing House.

The authors are:

David Allen
Gareth Beale
Nicole Beale
Chris Elmer
Jude Jones
Kristian Strutt
Clare Allen
Daniel Jones

There are three posts that make up this report. The post below describes the excavation and recording methodology and outlines the research question for the dig for 2013. Two further posts describe the finds and also the geophysical survey that was started in Spring 2013 and which continued through the Summer of 2013. 

Part 3 – Geophysical Survey

– By Kristian Strutt and Clare Allen

The summer season of survey work was undertaken on Basingstoke Common, using GPS and Magnetometry. This survey work was part of an MSc dissertation and aimed to develop on the spring season of survey work. The main aim of the research was to examine the potential archaeology on the common and to assess the nature of these features through the use of geophysical survey. Using interpretation from previous survey results, an examination of aerial photographs and an analysis of the historical background of Basing House; the methodological approach to the survey was to use magnetometry. It was apparent that this technique would be suited to the potential nature of archaeology existing on the common. The site complex demonstrates a palimpsest of archaeology from prehistory to the English Civil War and 20th century wartime defences. With this in mind, it was possible to examine the defensive role of Basing House and its environs.

Magnetometer survey was carried out using a Bartington Instruments Grad 601 dual sensor fluxgate gradiometer. Readings were taken at 0.25m intervals along the traverses, with traverses spaced at 0.5m intervals. This technique was used to survey the site grounds and Basingstoke Common. This technique seemed most suited to both the environmental conditions and the potential nature of the archaeology at Basing House.

The results of the survey (see figures 2 and 3 below) indicated a number of archaeological features associated with the prehistoric, Civil War and 20th century defensive archaeology of the site. A ditch feature associated with the prehistoric or medieval settlement of the ridge is visible enclosing part of the common, running into the curtilage of Basing House and being cut by the Civil War defences. The half-moon earthworks of the Royalist defences show clearly in the magnetometry, including the ditch and possible remains of the palisades. The possible location of Parliamentarian siegeworks close to the site are, however, more difficult to trace. It is possible that the siegeworks are located along the line of the present hedgerow and fenceline, less than 30m from the defences of Basing House. The results of the survey did reveal the line of a substantial World War II anti-tank ditch, running from north-east to south-west across the common. This evidence is supported by air photographic evidence from the 1940s, indicating the defensive role of Basing House in the landscape surrounding the River Loddon. There remains scope for future geophysical survey at the site across the common and in areas surrounding Basing village, to help the team understand the buried archaeological deposits associated with Basing House.

You can click on the figures below to go to the Flickr page for the image, where larger versions are available.

This map shows the magnetometry survey areas from Basing House. Figure by K. Strutt and C. Allen, 2013.

Figure 2 – This map shows the magnetometry survey areas from Basing House. Figure by K. Strutt and C. Allen, 2013.

This map shows the magnetometry results from Basingstoke Common. Figure by K. Strutt and C. Allen, 2013.

Figure 3 – This map shows the magnetometry results from Basingstoke Common. Figure by K. Strutt and C. Allen, 2013.

References

Allen, D., S. Anderson, 1999. Basing House, Hampshire. Excavations 1978-1991, Hampshire Field Club and Archaeological Society Monograph Series

Combley, R.C., J. W. Notman, H. H. M. Pike, 1964. Further Excavations at Basing House, 1964-66.  Proceedings of the Hampshire Field Club. 23: 96-105

Peers, C., Sir. 1909. On the Excavation of the Site of Basing House, Hampshire. Archaeologia, Miscellaneous Tracts relating to Antiquity. London: Society of Antiquaries 61: 553-564

Read the previous posts of this Interim Report:

– Introduction and Recording Methodology

– Finds


Filed under: Clare Allen, Geophysical Survey, Interim Report 2013, Kris Strutt, Magnetometry Survey, Spring Survey, Summer Excavation Tagged: 1940s, aerial photographs, anti-tank ditch, Bartington Instruments, basingstoke common, defenses, earthworks, gps, gradiometer, half-moon, interim report, magnetometry, Old Basing, palisades, river Loddon, survey, total station survey, World War II

Photos of the Dig

We’ve been adding all of our photos to the Flickr Group. It would be great to see all of the photos that you took while you were at Basing House, so if you have any pictures that you’d like to share, please consider adding them to the Flickr Group. Alternatively, you can share photos with […]

We’ve been adding all of our photos to the Flickr Group.

It would be great to see all of the photos that you took while you were at Basing House, so if you have any pictures that you’d like to share, please consider adding them to the Flickr Group.

Alternatively, you can share photos with us on our Facebook page: http://www.facebook.com/pages/basinghousecat/

You can see all of our photos at our Basing House CAT Project Flickr Group: http://www.flickr.com/groups/basinghousecat/


Filed under: Archaeologist Portraits, Images, Spring Survey, Student Trips, Summer Excavation Tagged: flickr, images, photos, portraits, sharing

Guest Blog: Will Heard – Spring 2013 Survey Results Part 2

Last week we published a guest post from Will Heard, as a summary of the Spring Survey that the University of Southampton students carried out this April-May. Here is Will’s second and final blog post about the survey results. Thanks again to Will! — Basing House Spring Survey Part 2 by Will Heard, 2013 Will […]

Last week we published a guest post from Will Heard, as a summary of the Spring Survey that the University of Southampton students carried out this April-May. Here is Will’s second and final blog post about the survey results.

Will Heard

Will Heard

Thanks again to Will!

Basing House Spring Survey Part 2

by Will Heard, 2013
Will is a third year undergraduate student, with interests in survey, geophysics and the use of computers for archaeological purposes. He is interested in any period of history, having worked at Basing House and on a Bronze Age site amongst others.  He is currently working on his undergraduate dissertation, which aims to use GIS systems to reveal the theoretical effectiveness against invasion of a small section of the World War II G.H.Q Line in Essex.

The Motte Resistivity Survey

Figure 2 shows the resistivity plot of part of the Motte interior with notable features enclosed in coloured lines. The bottom left high resistivity feature is most probably related to the still accessible cellar, which can be seen as a large depression on the contours.

The  high resistivity feature at the far bottom of the image has no associated topographic evidence, but it is situated in a position that may suggest it is a continuation of the feature running parallel to the cellar. If this is so, then the high resistivity feature next to the cellar may not be directly related to  it after all. The other most interesting feature is the slight low resistance feature highlighted in green, which represents a dip on the topographic model. The ground raises up to a point which is a well (circled white in Figure 3). The presence of the well leads to the assumption that this area was some sort of courtyard or open air space. This is supported by Peer’s plan of his excavations (Figure 1).

Figure 1 - Plan of the Old House as excavated by Peers. After (Royal Archaeological Institute 1924: 362).

Figure 1 – Plan of the Old House as excavated by Peers. After (Royal Archaeological Institute 1924: 362).

Figure 2 - Resistivity Survey of part of the motte interior. Notable features are enclosed by coloured lines. Negative ohm values caused by the high pass filter. Contours from a raster. ArcGIS 10.1.

Figure 2 – Resistivity Survey of part of the motte interior. Notable features are enclosed by coloured lines. Negative ohm values caused by the high pass filter. Contours from a raster. ArcGIS 10.1.

Figure 3  - Motte interior resistivity draped over the 3D TIN surface. From the north. Light from the east at 45 degrees. Vertical exaggeration at 1.5.

Figure 3 – Motte interior resistivity draped over the 3D TIN surface. From the north. Light from the east at 45 degrees. Vertical exaggeration at 1.5.

The New House Resistivity Survey

The New House site was the largest of the three areas surveyed with Resistivity and has a lot of strong features. The most obvious features are the straight lines along the entire left side of Figure 13. These are undoubtedly buried foundations of the raised New House.

The circular anomalies are towers of the sort seen in Hollar’s drawing (see Figure 15). The strength of these anomalies suggests excellent preservation and indeed, an excavation uncovered some of these remains and did not fully fill in the trenches. The resulting depression in the topography can be seen in the foreground of Figure 14.

The very low (white) anomalies in the same area are possibly caused by a slow build-up of moist, humic soils in the unfilled excavation trenches. Given the aforementioned evidence, it appears unlikely the anomalies are of historical origin. However, further south in Figure 13, some of the unexcavated strong circular anomalies enclose areas of extremely low resistance. These may be the result of filled sunken floors, or quarrying straight after the final Civil War siege.

Another area of interest is on the right of Figure 13, which is circled by a green line. This area is highly variable, with pixels of very high and low resistance and it is unclear what these readings represent. More areas of interest include the horizontal line feature and various other patches of high resistance in Figure 13.

Figure 4 - Resistivity Survey of the New House area. Notable features are enclosed by coloured lines. Negative ohm values caused by the high pass filter. Contours from a raster. ArcGIS 10.1.

Figure 4 – Resistivity Survey of the New House area. Notable features are enclosed by coloured lines. Negative ohm values caused by the high pass filter. Contours from a raster. ArcGIS 10.1.

Figure 5 - New House resistivity plot draped over the 3D TIN. Red lines show features with associated topographic variations. From the north. Light from the east at 45 degrees. Vertical exaggeration at 1.5. ArcGIS 10.1.

Figure 5 – New House resistivity plot draped over the 3D TIN. Red lines show features with associated topographic variations. From the north. Light from the east at 45 degrees. Vertical exaggeration at 1.5. ArcGIS 10.1.

Figure 6 - Wenceslaus Hollar's 'The Siege of Basing House'. The text reads 'A THE OLD HOUSE. B. THE NEW. C. THE TOWER THAT IS HALFE BATTERED DOWN. D. KINGS BREASTWORKS. E. PARLAMENTS BREASTWORKS' [sic]. After (Wikipedia 2013)

Figure 6 – Wenceslaus Hollar’s ‘The Siege of Basing House’. The text reads ‘A THE OLD HOUSE. B. THE NEW. C. THE TOWER THAT IS HALFE BATTERED DOWN. D. KINGS BREASTWORKS. E. PARLAMENTS BREASTWORKS’ [sic]. After (Wikipedia 2013)

Everyone was very pleased with how the survey went, despite some bitterly cold days and an afternoon of menacing weather in the first week. I hope that these highlights from the data illustrate just what can be done with all the data we gathered although someone more savvy with the computer software could do things much more impressive than this. Various sub-surface features were linked to surface features observable on the topographic model.  Some of these were easily dated thanks to their close proximity to known quantities, like the New House, while others were less easily identifiable. The lack of confident dates on numerous features is a reason for more work, especially excavation, on site in the future. Lastly, I would personally encourage anybody who has not been before, to go and see this great site.

References

(1924). Proceedings at Meetings of the Royal Archaeological Institute. The Archaeological Journal 81. Royal Archaeological Institute. 315-380. (Basing House pp. 359-364).

English Heritage (last updated 2004). National Monuments Record, Basing House. at: http://archaeologydataservice.ac.uk/archsearch/record.jsf?titleId=1033242; 27 Feb. 2013.

English Heritage. (2007a). Pastscape, Basing House at: http://www.pastscape.org.uk/hob.aspx?hob_id=240444; 01 May 2013.

Wikipedia. (2013). Wenesclaus Hollar – The Siege of Basing House at: http://en.wikipedia.org/wiki/File:Wenceslaus_Hollar_-_The_Siege_of_Basing_House.jpg; 6 Mar 2013.

Wikipedia. (2013). Launceston Castle at: http://en.wikipedia.org/wiki/File:Launceston_Castle_-_geograph.org.uk_-_22242.jpg; 12 Jul 13


Filed under: Spring Survey, Student Research Post, Will Heard Tagged: building survey, gpr, gps, ground penetrating radar, leica, magnetic susceptibility, magnetometry, new house, old house, resistance survey, resistivity, survey, surveying, topographic, total station, undergraduate

Guest Blog: Will Heard – Spring 2013 Survey Results Part 1

As part of the Spring Survey that the University of Southampton students carried out this April-May, undergraduate Archaeology students who attended the fieldwork were asked to write a report summarising the survey data. One of the students that attended the Spring Survey, Will Heard, has written a summary of his report, and has kindly allowed […]

As part of the Spring Survey that the University of Southampton students carried out this April-May, undergraduate Archaeology students who attended the fieldwork were asked to write a report summarising the survey data.

One of the students that attended the Spring Survey, Will Heard, has written a summary of his report, and has kindly allowed us to share it with our readers. Will has written so much, that we’re sharing part 1 this week, and part 2 next week!

Thanks Will!

Basing House Spring Survey Part 1

Will Heard

Will Heard

by Will Heard, 2013
Will is a third year undergraduate student, with interests in survey, geophysics and the use of computers for archaeological purposes. He is interested in any period of history, having worked at Basing House and on a Bronze Age site amongst others.  He is currently working on his undergraduate dissertation, which aims to use GIS systems to reveal the theoretical effectiveness against invasion of a small section of the World War II G.H.Q Line in Essex.

Survey Summary

During March and April 2013 a topographic and geophysical survey was undertaken at Basing House by University of Southampton staff and students. Most of the topographic survey was carried out in week one between the 18th and 22nd March, while all of the geophysical survey was carried out in week two, between the 8th and 12th April. The work aimed to further the understanding of the sites layout and history by providing a computer model which will allow more detailed analysis of the landscape, and possibly help us see things our naked eyes cannot. The model will consolidate much of the smaller scale on site investigation (excavations, geophysics) which have been carried out and documented in the past. Similarly, future work of all types will be able to use the model to add onto a coherent body of knowledge. The geophysical and building survey, which was carried out alongside the topographic work, will add to this body of knowledge on Basing House.

Introducing the Site

The area has a long history with the earliest known finds dating from the Mesolithic era, although this occupation is not currently seen as continuing, since Neolithic remains are rare to nonexistent on the site (English Heritage 2004). Bronze Age flint, as well as Iron Age and Roman ceramics have also been recovered (English Heritage 2004). The most discussed period of the sites history starts in the Medieval period, with the construction of the Motte and Bailey castle (see central round and plateau like feature in figure 1) and later the Old and New Houses (inside and to the east of the motte in figure 1). The Motte and Bailey were erected sometime in the twelfth century AD and the Old and New Houses erected one after the other in the sixteenth century AD. The New House merited its own earthworks to the east of the Motte and Bailey and later, semi-circular Civil War gun platforms were added onto the earlier Medieval outer bank to the south. After the Civil War the houses were demolished, with much of the stonework taken and used in the nearby village. Other features include a dry and filled in part of the eighteenth century Basingstoke Canal (north edge of figure 1).

Figure 1 - OS Map data with a polygon overlaid (red line). The polygon represents the extent of the area surveyed topographically. ArcGIS 10.1. © Crown Copyright/database right 2013. An Ordnance Survey/EDINA supplied service.

Figure 1 – OS Map data with a polygon overlaid (red line). The polygon represents the extent of the area surveyed topographically. ArcGIS 10.1.
© Crown Copyright/database right 2013. An Ordnance Survey/EDINA supplied service.

Below, figure 2 shows the areas that were surveyed with resistivity equipment. The contours in this figure are derived from a raster.

Figure 2 - The area surveyed with resistivity equipment (contours derived from a raster). ArcGIS 10.1. © Crown Copyright/database right 2013. An Ordnance Survey/EDINA supplied service.

Figure 2 – The area surveyed with resistivity equipment (contours derived from a raster). ArcGIS 10.1.
© Crown Copyright/database right 2013. An Ordnance Survey/EDINA supplied service.

Since the survey produced one continuous area of data (see figure 3 and figure 4 below), the following pictures have some degree of overlap. The area has been split into four areas: A, B, C and D. The topographic areas B and C are the highlights included in this week’s blog post. In terms of the resistivity survey, the highlights were the Motte interior survey and the New House site survey.

Figure 3 - Basing House complete TIN with features overlain. ArcGIS 10.1

Figure 3 – Basing House complete TIN with features overlain. ArcGIS 10.1

Figure 4 - Basing House complete Raster with features overlain. ArcGIS 10.1

Figure 4 – Basing House complete Raster with features overlain. ArcGIS 10.1

Area B

Area B is the southernmost area surveyed and has the highest general elevation of any of this report’s areas. It comprises what is thought to be a long semi-circular bank that was possibly constructed at a similar time to the Motte and Bailey, as well as three Civil War raised gun platforms (English Heritage 2007a). These are clearly visible on the ground and are highlighted in figure 5. It is possible that the fact the three gun platforms are attached to the bank means that the bank was constructed earlier, since a connecting bank between Civil War gun platforms would not always be necessary. In the Civil War, the bank would have provided good cover against bombardment or assault from the south and so adding gun platforms to an already good fortification was the logical course of action. At points the ditch protecting the bank is deeper, for example at the westernmost end. Towards the southern end the ditch becomes very shallow. This variation is probably due to the natural topography, which gets higher as one goes further south on our model, this variation is highlighted in figure 6 below.

Figure 5 -  Area B TIN and Raster. ArcGIS 10.1.

Figure 5 – Area B TIN and Raster. ArcGIS 10.1.

Figure 6 - Area B 3D TIN with features added. From the east. Light from the east at 45 degrees. Vertical exaggeration at 1.5. ArcGIS 10.1.

Figure 6 – Area B 3D TIN with features added. From the east. Light from the east at 45 degrees. Vertical exaggeration at 1.5. ArcGIS 10.1.

Area C

Area C is the centre of the topographic survey area and comprises the Motte, Bailey and their respective ditches. The elevation of this area is generally quite high, while being lower than Area B (see figures 7 and 8 below).

Figure 7 - Area C TIN and Raster. ArcGIS 10.1.

Figure 7 – Area C TIN and Raster. ArcGIS 10.1.

Figure 8 - Area C 3D TIN with features added. From the west. Light coming from the east at 45 degrees. Vertical exaggeration at 1.5.

Figure 8 – Area C 3D TIN with features added. From the west. Light coming from the east at 45 degrees. Vertical exaggeration at 1.5.

The Motte and Bailey ditches are very deep, survive very well and show very nicely on the topographic models. All of the surviving cellars inside the motte lend support to Peer’s plan (figure 9 below).

Figure 9 - Plan of the Old House as excavated by Peers. After (Royal Archaeological Institute 1924: 362).

Figure 9 – Plan of the Old House as excavated by Peers.
After (Royal Archaeological Institute 1924: 362).

The variations on the east side of the bailey are caused by a previous excavation that was carried out before a bridge over the ditch was constructed. The yellow line (north side of figure 8 above) represents a raised piece of ground and is the location of a large tree.

The topographic model shows the Motte being higher than the Bailey. This is to be expected, both because the land naturally goes down northwards, but also because the Motte was where the Lord would have resided.

The form of the Motte and Bailey is very similar to other examples like Launceston Castle (figure 10 below).

Figure 10 - Launceston Castle. In size, it is smaller than Basing House. However, its Motte and Bailey design is similar. After (Wikipedia 2013)

Figure 10 – Launceston Castle. In size, it is smaller than Basing House. However, its Motte and Bailey design is similar.
After (Wikipedia 2013)

References

Anon. (1924). Proceedings at Meetings of the Royal Archaeological Institute. The Archaeological Journal 81. Royal Archaeological Institute. 315-380. (Basing House pp. 359-364).

English Heritage (last updated 2004). National Monuments Record, Basing House. at: http://archaeologydataservice.ac.uk/archsearch/record.jsf?titleId=1033242; 27 Feb. 2013.

English Heritage. (2007a). Pastscape, Basing House at: http://www.pastscape.org.uk/hob.aspx?hob_id=240444; 01 May 2013.

Wikipedia. (2013). Wenesclaus Hollar – The Siege of Basing House at: http://en.wikipedia.org/wiki/File:Wenceslaus_Hollar_-_The_Siege_of_Basing_House.jpg; 6 Mar 2013.

Wikipedia. (2013). Launceston Castle at: http://en.wikipedia.org/wiki/File:Launceston_Castle_-_geograph.org.uk_-_22242.jpg; 12 Jul 13

Next Week: Part 2

In the next post, we’ll look at the results from the Motte resistivity survey and the New House resistivity survey.


Filed under: Spring Survey, Student Research Post, Will Heard Tagged: building survey, gpr, gps, ground penetrating radar, magnetic susceptibility, magnetometry, new house, old house, resistance survey, resistivity, survey, topographic, total station, undergraduate, will-heard

Spring Survey – Week 2 Review

The undergraduates have finished working at Basing House for this Spring, and we’ll be back on site in a few weeks to collect  more data for some of our postgraduate students who are using the site for various projects. This is the team from Week 2. I can’t believe how much ground these guys covered! […]

The undergraduates have finished working at Basing House for this Spring, and we’ll be back on site in a few weeks to collect  more data for some of our postgraduate students who are using the site for various projects.

This is the team from Week 2. I can’t believe how much ground these guys covered! Thanks all!

Spring Survey – Week 2 Team

I thought it might be useful to give you a rundown on the different tools that we were using to record the site during the topographic, building and geophysical survey, as we keep saying things like ‘mag’ and ‘GPR’ without explaining what any of them are!

In our next post, we’ll begin to share the results of the surveys, so do check back regularly, or subscribe to the blog for updates, using the link on the navigation to the right.

Geophysical Survey

There are a few pieces of kit that we use for a geophysical survey.

Magnetometry

Magnetometry

Magnetic survey uses a magnetometer to identify the presence of magnetised iron oxides in the soil. Magnetometers are great for identifying ferrous oxides or burnt/ heated material that show up as ‘positive’ features, as well being great for finding negative features, like a pit or a ditch.  Magnetometers are great for identifying industrial areas, and buildings.

The magnetometer you see in these photos is a Fluxgate Gradiometer, which is the most commonly used type in the UK. With this instrument, we take two readings at a time.  The vertical poles on either end of the horizontal handle are the sensor-sets. Within each of the poles there are two sensors, one at the top and one at the bottom. The reading that we are measuring is the difference between the top sensor and the bottom sensor. The fluxgate sensors are always a set distance apart, normally half a metre or a metre (in this instrument, they are a metre apart).

The sensors are very sensitive and so when you are using one, you must be careful not to be wearing anything metal. As you can see from the photograph below, this often makes attire a bit unusual. Tracksuit trousers are the best option, and cheap wellies work well for footwear. Belts are an absolute no-no, and raincoats with lots of zips and poppers must be avoided. The higher up your body the metal is, the less likely it is to affect the instrument. So piercings and glasses with metal frames are sometimes okay, but ideally, should be removed.

The person operating the instrument will walk up and down in a grid of between 10-30 metres. Each grid is marked out on the ground, normally using bamboo canes placed at intervals (every two metres is a good way to do it), and the person carrying the instrument can use these canes as markers to aim for to ensure their line is aligned correctly within the grid.  You can collect the data by walking parallel lines, or in a zigzag shape.

Magnetometry – note the poncho – a coat with no metal in it is hard to find!

Magnetic Susceptibility

Magnetic Susceptibility

Magnetic susceptibility is possible because material can become temporarily magnetised: Any human activity will affect soil magnetic susceptibility. Ideally what we’re searching for is topsoil that has been affected by features buried underneath it.  Magnetic Susceptibility can be collected in continuous or single measurements. The instrument sends out a magnetic pulse, and measures the ability of the soil to hold a magnetic charge.  Human activity affects the chemical makeup of the soil, so magnetic susceptibility will be affected by this, and can be used to pick up on things like areas of a settlement where there has been lots of rubbish deposited or farming activity taking place.

To the right of this photograph, Crystal is holding the GPS; more about that piece of kit later in this post…

Resistance Survey

Resistance survey

Resistance survey works by feeding an electric current into the soil.  Sub-surface materials all have varying resistivities to an electrical current. With this technique, we measure these values, and in so doing can build up a picture of what is under the surface. Generally walls and other positive features such as trackways, cists, rubble and man-made surfaces result in high resistance, and negative features such as ditches, drains, graves, and pits result in low resistance. This is because negative features tend to have higher moisture content.

Depending upon the material and the water content, features can show up as either positive or negative. Typically stone features are high resistance, whereas ditches, depending upon their fill are negative (or low) resistance. The resistance of materials under the ground uses the ability of soil to let electric current pass through it, and this is related to the interstitial water (i.e. water in the gaps in-between) and salts within the soil.

On the last day of the survey, we had to abandon the resistance survey because there was the chance of the results being ruined by the heavy rain, and standing water.

Ground Penetrating Radar (GPR)

Ground Penetrating Radar

Ground Penetrating Radar works by firing radar pulses into the ground and recording the speed at which the signals are reflected back to the device.  These varying reflections allow a picture to be built up of the sub surface topography. GPR data are recorded in traverses, but are then joined together and sliced to produce flat layers, each layer representing measurements at a particular depth. These layers are known as time slices and can be ‘stacked up’ to provide a 3D model of the subsurface topography.  GPR is particularly good at detecting brick or stone foundations and is especially useful as it provides relative depth measurements.

Building Survey

Total Station with red laser

Total Station

In the photograph above, Dan is using a using a Total Station to carry out a building survey of the Old House.  There are two ways to use a Total Station to survey standing remains.

The total station is an electronic theodolite, which has an electronic distance meter which measure the distance and angles from the total station to a particular point. A laser is used to make this measurement. The total station sends out a beam which can either meet the surface that is being recorded, showing up as a red light (as is in the photographs above and below) or can meet with a target in the form of a prism, mounted on a staff of a fixed height.

In the first method, the building remains themselves are the target, and point by point the shape of the walls and features are recorded by the total station operator. For the Old House, the teams began with the top and bottom edges of the brickwork, and then surveyed in additional features, such as the bread ovens, doors and window frames.

Total Station with TheoLT – seeing the data live

Topographic Survey

Total Station with prism

The alternative method, involves using the machine on the tripod as a base station.  This is for the recording of changes in landscape. The total station remains in the same place, and a prism (see the photograph below) is used as a target.  The prism is moved around the site, and at each point where there is a significant change in topography (or at regular intervals, of around 5 metres) the total station operator matches the laser from the total station to the target prism and records the point.

Survey Prisms

When carrying out a survey on a site the size of Basing House, its good practice to set up base stations across the site.  We initially had fourteen base stations, which we added at the beginning of the survey. But the students had to add more, in order to record more problematic areas of the site. For instance, the ditch around the motte and bailey was hard to record without adding lots of stations all of the way round, in order for each base station to ‘see’ back to the previous station, and on to the next one.

Below, Dom is using the GPS to log a base station before we began the survey on site. Chris and Tim are adding wooden pegs in the spot that the GPS is recording; this becomes the base station.

Setting out the base stations with a total station

Global Positioning System (GPS)

A GPS uses the NAVSTAR GPS, which is a system which uses a collection of 24 satellites, controlled by the US Department of Defence, which are orbiting the earth. The GPS communicates via a signal with the satellites using a radio receiver, to work out its geographical position – this is possible because the GPS can compute the distance from the satellite by multiplying the velocity with the time the signals take to transmit from the satellite. The more satellites in range of the GPS, the better. The GPS needs a minimum of three satellites to be able to tell where it is on a horizontal plane, and at least four satellites to calculate where it is 3-dimensionally; i.e. the latitude, the longitude and the height.

Global Positioning System (GPS)

At Basing House, we used the GPS as described above; as a positioning tool, to tell us where something was; we used it both for the magnetic susceptibility data, and also for adding the base stations. But GPS can also be used as a surveying tool. In the photograph above, Lizzie is using the GPS to survey in the gatehouse of the Old House. The GPS can record the location of a series of points, so we used it to fill in gaps of the topographic survey, and the building survey. In the photograph below, you can see some of the points that we recorded up on the Bailey. I walked up and down in a grid, and took points at regular intervals, to build up a record of the topography of the Bailey.

GPS screen

Finding out more about Geophysics

I used Gaffney, C., Gater, J. (2006). Revealing the Buried Past: Geophysics for Archaeologists, The History Press: Stroud to write this blog post (my geophysics is a bit rusty and I wanted to make sure the iformation was up to date!). I really do recommend this book if you want to find out more about Geophysics prospection for archaeology.

The Archaeological Prospection Service at Southampton (APSS) website – http://www.southampton.ac.uk/archaeology/apss/ -  is also a great place to read about geophysics. Kris Strutt writes an excellent blog – http://kdstrutt.wordpress.com/ - which covers some of the work that he does with the APSS, so follow his posts to keep up to date with the projects that the team is involved in.


Filed under: Spring Survey, Survey Equipment Tagged: equipment, geophysics, global positioning system, gpr, gps, ground penetrating radar, leica, magnetic susceptibility, magnetometry, prism, resistivity, satellites, theolt, topographic, total station

Basing House Survey Final Day – A rain check and some reflections

Reblogged from Kristian Strutt: The second week of survey at Basing House finished on Friday in a spray of mud and rain, hailstones and inky cloud. What had promised to be a reasonable day quickly became unworkable, wet and cold. The teams set out for the final day of survey, focusing on completion of the […]

Reblogged from Kristian Strutt:

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The second week of survey at Basing House finished on Friday in a spray of mud and rain, hailstones and inky cloud. What had promised to be a reasonable day quickly became unworkable, wet and cold. The teams set out for the final day of survey, focusing on completion of the magnetometry and resistivity in the area of the New House and outer bailey, and GPR over the outer bailey also.

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Kris Strutt's blog on Day Five of the Week Two geophysics work at Basing House.

Basing House Survey, Day Four – Spring finally arrives!

Reblogged from Kristian Strutt: We have had some really productive days on the second phase of survey at Basing House, with third year and postgraduate students from the University of Southamotin working hard, and carrying out resistance survey, magnetometry, GPR and magnetic susceptibility of the Old and New houses, and Civil War defences and the […]

Reblogged from Kristian Strutt:

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We have had some really productive days on the second phase of survey at Basing House, with third year and postgraduate students from the University of Southamotin working hard, and carrying out resistance survey, magnetometry, GPR and magnetic susceptibility of the Old and New houses, and Civil War defences and the outer bailey. Spring also finally arrived today after single-figure temperatures and damp weather.

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Week Two, Day Four by Kris Strutt.

Basing House Spring Survey – Week 2 Day One

Reblogged from Kristian Strutt: After a few weeks out of the field, the staff and students from the University of Southampton arrived back at Basing House to start the geophysical survey component of the fieldwork. A mix of third year students from Archaeology and Oceanography, Erasmus students and postgraduates headed out to the site. Chris […]

Reblogged from Kristian Strutt:

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After a few weeks out of the field, the staff and students from the University of Southampton arrived back at Basing House to start the geophysical survey component of the fieldwork. A mix of third year students from Archaeology and Oceanography, Erasmus students and postgraduates headed out to the site. Chris Elmer again gave the group a tour of the site, while supervisors commenced gridding out the site using Smartnet GPS.

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Week Two, Day One by Kris Strutt.

Spring Survey Week One – Day Four

Today was a cold but very productive day up at Basing House. The student teams are getting faster at recording topography and have covered huge areas of the site. Surveying in the limits of the New House has been tricky as there are partial walls to try to identify. One of the student teams is […]

Today was a cold but very productive day up at Basing House.

Preparing for day four of the topographic and building survey. March 2013.

The student teams are getting faster at recording topography and have covered huge areas of the site.

On day four, students have been surveying the earthworks at the south east of the site.

Surveying in the limits of the New House has been tricky as there are partial walls to try to identify.

Surveying the New House stables.

One of the student teams is made up of Masters students, two of whom are planning to use Basing House as the major case study for their dissertation projects. The Masters students were working on surveying the very complex interior of the Old House today. It was out of the wind, but still very cold!

The interior of the Old House today. It was out of the wind, but still very cold!

I started a photographic suvey of the various grafitti on the site. The photos below show examples of the variety of graffiti in the Old House etched into the plaster. We’re planning to use some new computational photography techniques to record this in the summer.

Grafitti in the Old House.

Grafitti in the Old House.

There is also lots of grafitti elsewhere on the site. This stone column is mounted in the wall of the Bothy, in amongst the corbels, and has a great picture of a man with what looks like a huge feather in his hat. We’ll be recording it all later this year.The corbels with their grotesque and animal faces are really fantastic. I think these would be great to record using photogrammetry to create 3D models of them as a record.

There are lots of corbels and graffitied stonework sections that I will use photogrammetry to record in the next week of surveying in April.

There are lots of stonework details around the site that have been reused to support various parts of the excavated ruins that I have started recording. It would be great to record these in detail and begin to think about finding out more about the various pieces of masonry. You can see from the images below that there are some really very high quality window and door details being used to prop up earth banks. These were put here in the late 1800s, so the ‘new’ location is just as historically interesting as the stone pieces’ original use.

In the late 1800s, much of the discovered stonework was reused to create features and support brickwork. It’d be great to record this in the summer.

Some more reused stonework in the Old House hall cellar.

Stonework resituated in the Old House.

We’ve been having a few visitors to the site over the past week, as Basing House is open to the public and we are happy to chat to people as they walk by. There have also been some visitors from local societies. Tim Sly has been printing daily reference images for the students to use as quick reference checks to ensure that we are covering the entire site, and these have been very handy to use to show interested visitors what we have been getting up to.

This is a TIN (a map of 3D data created automatically from the points the student teams have been surveying in) with some contours on it. Its only a small part of the larger survey that we have been doing, but it gives an idea of the high quality of the data that the teams have been collecting.

We had visitors today. Here, Tim and I are showing someone a print out of some of the data the students have been producing.

Lizzie Richley has been using the GPS since Wednesday to record parts of the site that the student teams are finding are difficult to survey using a total station. The GPS that we have been using does not need a base camp and so there is no cumbersome backpack to carry around. Lizzie showed me how the new GPS works, and I had a great time surveying in part of the motte and bailey this afternoon.

Lizzie spent time showing me the new GPS today., Here we are in the entrance of the Old House.

The new GPS has a function to see a map of all of the spot points, lines and areas that you have surveyed in. Its so satisfying to see all of the points appear as you walk the area that you are recording.

Using the GPS to survey parts of the site that would take a long time to use a total station to record.

Lizzie spent time showing me the new GPS today., Here we are in the entrance of the Old House.

Using the GPS to survey in spot points on the motte and bailey.

The GPS is great, but the stars of the show really are the student surveying teams. The work that they have been doing is really great. They have been working together to collect great quality data that will result in one of the first comprehensive surveys of Basing House. Without them this survey really would not have been possible. All 25 students and 8 staff members have been giving 100% to ensure that we get topographic coverage across the whole of the site; not to mention the additional building survey, which will give us a clear record of the Great Barn interior.

Tomorrow is the last day for this first part of the survey (we continue again with geophysics between the 8th – 12th April), and there is heavy rain forecast for the afternoon, so we will be working even harder to try to finish the survey before the rain sets in. So wish us luck!

Surveying the New House.


Filed under: Spring Survey Tagged: building survey, corbels, festival of british archaeology, grafitti, kdstrutt, knot garden, leica, new house, old house, photogrammetry, rain, recording, rti, stonework, survey, surveying, topographic, total station, undergraduate