Land West of Elm Grove Ebrington Gloucestershire2.3 Data processing and presentation 2.3.1 Magnetometry data downloaded from the Grad 601-2 data logger are analysed and processed in

Land West of Elm Grove

Ebrington

Gloucestershire

MAGNETOMETER SURVEY REPORT

for

Wolverley Homes

David Sabin and Kerry Donaldson

March 2009

Ref. no. 271

Archaeological Surveys Ltd

ARCHAEOLOGICAL SURVEYS LTD

Land West of Elm Grove

Ebrington

Gloucestershire

Magnetometer Survey

for

Wolverley Homes

Fieldwork by David Sabin and Francis SabinReport by David Sabin BSc (Hons) MIFA and Kerry Donaldson BSc (Hons)

Survey date - 17th March 2009 Ordnance Survey Grid Reference – SP 18910 40145

Printed on 100% recycled paper

Archaeological Surveys LtdPO Box 2862, Castle Combe, Chippenham, Wiltshire, SN14 7WZ

Tel: 01249 782234 Fax: 0871 661 8804Email: [email protected]: www.archaeological-surveys.co.uk

Archaeological Surveys Ltd is a company registered in England and Wales under registration number 6090102, Vat Reg no. 850 4641 37.Registered office address, Griffon House, Seagry Heath, Great Somerford, Chippenham, SN15 5EN.

Archaeological Surveys Ltd Land West of Elm Grove, Ebrington Magnetometer Survey

CONTENTS

SUMMARY.........................................................................................................................1

1 INTRODUCTION..............................................................................................................1

1.1 Survey background...................................................................................................1

1.2 Survey objectives and techniques.............................................................................1

1.3 Site location, description and survey conditions........................................................1

1.4 Site history and archaeological potential...................................................................2

1.5 Geology and soils......................................................................................................2

2 METHODOLOGY.............................................................................................................2

2.1 Technical synopsis....................................................................................................2

2.2 Equipment configuration, data collection and survey detail.......................................3

2.3 Data processing and presentation.............................................................................4

3 RESULTS.........................................................................................................................6

3.1 General overview......................................................................................................6

3.2 List of anomalies ......................................................................................................7

4 DISCUSSION...................................................................................................................9

5 CONCLUSION.................................................................................................................9

6 REFERENCES...............................................................................................................10

Appendix A – basic principles of magnetic survey............................................................11

Appendix B – survey and data information.......................................................................12

Appendix C – digital archive.............................................................................................13

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LIST OF FIGURES

Figure 01 Map of survey area (1:25 000)

Figure 02 Referencing information (1:1000)

Figure 03 Greyscale plot of raw magnetometer data (1:1000)

Figure 04 Trace plot of raw magnetometer data (1:1000)

Figure 05 Greyscale plot of processed magnetometer data (1:1000)

Figure 06 Abstraction and interpretation of magnetic anomalies (1:1000)

LIST OF TABLES

Table 1: Bartington fluxgate gradiometer sensor calibration results.....................................4

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SUMMARY

A detailed magnetometry survey was carried out over approximately 1.3ha atEbrington, Gloucestershire.The survey located linear, curvilinear and discrete anomalies across much of thesurvey area. Several linear and curvilinear positive anomalies appear to indicatepossible enclosures. Many anomalies could not be confidently interpreted from theirmorphological characteristics although the magnitude of the magnetic responsetends to suggest soils have been subject to intensive anthropogenic activity. Broadlinear anomalies typical of former ridge and furrow were located and may indicateagricultural disturbance to features across the site.The presence of Roman and Saxon archaeological sites in close proximity to thesurvey area, and the presence of Roman cultural material on the field surface,would tend to support an archaeological interpretation for a number of theanomalies located by the survey.

1 INTRODUCTION

1.1 Survey background

1.1.1 Archaeological Surveys Ltd was commissioned by The Historic EnvironmentConsultancy, on behalf of Wolverley Homes, to undertake a geophysicalsurvey of an area of land at Ebrington, Gloucestershire. The site has beenoutlined for the proposed development of 12 dwellings. The survey forms partof an archaeological assessment of the site.

1.1.2 An Archaeological Assessment, carried out by The Historic EnvironmentConsultancy (2009), has identified the site as of high archaeological potential.The site lies close to the remains of a Roman villa and a Saxon cemetery.

1.2 Survey objectives and techniques

1.2.1 The objective of the survey was to use magnetometry to locate geophysicalanomalies that may be archaeological in origin so that they may be assessedprior to development of the site.

1.2.2 Magnetometry is a highly effective and efficient means of archaeologicalprospection recommended for survey over large areas. The survey and reportgenerally follow the recommendations set out by English Heritage, 2008:Geophysical survey in archaeological field evaluation. .

1.3 Site location, description and survey conditions

1.3.1 The site is located on the eastern edge of Ebrington village in the northeastern corner of Gloucestershire. The site is centred on Ordnance SurveyGrid Reference SP 18910 40145.

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1.3.2 The geophysical survey covers an area of approximately 1.3ha of agriculturalland. At the time of survey, the site had been roughly ploughed and containeda variable cover of wild plant growth. The site slopes down to the south andeast where a number of springs emerge.

1.3.3 The survey conditions across the site were poor due to the rough state of theground surface. Weather conditions were fine.

1.4 Site history and archaeological potential

1.4.1 Many artefacts from the Prehistoric, Roman, Medieval and Post-Medievalperiods have been located within and surrounding the village of Ebrington.Specific sites include a substantial Roman villa (SAM 399), situatedapproximately 140m to the south of the survey area, which was partiallyexcavated during the 1950s and 1960s.

1.4.2 At least 68 Saxon burials have been located within a cemetery site,approximately 180m to the north of the development area. Medieval ridge andfurrow cultivation was also known to have occurred in the immediate vicinity.(The Historic Environment Consultancy, 2009).

1.4.3 The location of the site within an area containing several archaeological sitesand findspots, indicates that there is a high potential for locating geophysicalanomalies relating to archaeological features.

1.5 Geology and soils

1.5.1 The underlying geology is Middle Lias limestone (BGS, 2001).

1.5.2 The overlying soils across the site are from the Oxpasture association whichare stagnogleyic argillic brown earths. These consist of fine loamy overclayey soils with slowly permeable subsoils and slight seasonal waterlogging.(Soil Survey of England and Wales, 1983).

1.5.3 Magnetometry survey carried out over similar soils and geology have resultedin a good contrast between the fill of cut features and the subsoil into whichthey have been cut.

2 METHODOLOGY

2.1 Technical synopsis

2.1.1 Magnetometry survey records localised magnetic fields that can be associatedwith features formed by human activity. Magnetic susceptibility and magneticthermoremnance are factors associated with the formation of localised fields.Additional details are set out below and within Appendix A.

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2.1.2 Iron minerals within the soil may become altered by burning and the breakdown of biological material; effectively the magnetic susceptibility of the soil isincreased, and the iron minerals become magnetic in the presence of theEarth's magnetic field. Accumulations of magnetically enhanced soils withinfeatures, such as pits and ditches, may produce magnetic anomalies that canbe mapped by magnetic prospection.

2.1.3 Magnetic thermoremnance can occur when ferrous minerals have been heated tohigh temperatures, such as in a kiln, hearth, oven etc. On cooling, a permanentmagnetisation may be acquired due to the presence of the Earth's magnetic field.Certain natural processes, associated with the formation of some igneous andmetamorphic rock, may also result in magnetic thermoremnance.

2.1.4 The localised variations in magnetism are measured as sub-units of the Tesla,which is an SI unit of magnetic flux density. These sub-units are nano Teslas (nT),which are equivalent to 10⁻⁹ Tesla (T).

2.2 Equipment configuration, data collection and survey detail

2.2.1 The detailed magnetic survey was carried out using a Bartington Grad601-2gradiometer. This instrument effectively measures a magnetic gradientbetween two fluxgate sensors mounted vertically 1m apart. Two sets ofsensors are mounted on a single frame 1m apart horizontally. The instrumentis extremely sensitive and is able to measure magnetic variation to0.03nanoTesla (nT). All readings are saved to an integral data logger foranalysis and presentation.

2.2.2 The instrument is operated according to the manufacturer's instructions, withconsideration given to the local conditions. An adjustment procedure is required,prior to collection of data, in order to balance the sensors and remove the effects ofthe Earth's magnetic field; further adjustment is required during the survey due toinstrument drift often associated with temperature change. It may be very difficult toobtain optimum balance for the sensors, due to localised magnetic vectors that canbe associated with large ferrous objects, geological/pedological features, 'magnetic'debris within the topsoil and natural temperature fluctuations. Imperfect balanceresults in a heading error, often visible as striping within the data. This can beeffectively removed by software processing and generally has little effect on thedata unless extreme.

2.2.3 The Bartington gradiometer undergoes regular servicing and calibration by themanufacturer. A current assessment of the instrument is shown in Table 1 overleaf.

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Date ofcalibration/service

16th May 2008

Sensor type Bartington Grad - 01 – 1000 Nos. 084 and 085

Bandwidth 12Hz (100nT range) both sensors

Noise <100pT peak to peak

Adjustable errors <2nT

Table 1: Bartington fluxgate gradiometer sensor calibration results

The instrument was considered to be in good working order prior to thesurvey, with no known faults or defects.

2.2.4 Data were collected at 0.25m centres along traverses 1m apart. The surveyarea was separated into 30m by 30m grids giving 3600 recordedmeasurements per grid. This sampling interval is very effective at locatingarchaeological features and is the recommended methodology forarchaeological prospection (English Heritage, 2008).

2.2.5 The survey grids were set out to the Ordnance Survey OSGB36 datum usinga Penmap RTK GPS and aligned on the southern field boundary. The GPS isused in conjunction with Leica's Smartnet service, where positional correctionsare sent via a mobile telephone link. Positional accuracy of around 10 – 20mmis possible using the system.

2.3 Data processing and presentation

2.3.1 Magnetometry data downloaded from the Grad 601-2 data logger areanalysed and processed in specialist software known as ArcheoSurveyor.The software allows greyscale and trace plots to be produced for presentationand display. Survey grids are assembled to form an overall composite of data(composite file) creating a dataset of the complete survey area. Appendix Bcontains specific information, concerning the survey and data attributes, and isderived directly from ArcheoSurveyor; this should be used in conjunction withinformation provided by Figure 02.

2.3.2 Only minimal processing is carried out, in order to enhance the results of thesurvey for display. Raw data are always analysed as processing can modifyanomalies. The following schedule sets out the data and image processingused in this survey:

● clipping of the raw data at ±10nT to improve greyscale resolution,● clipping of processed data at ±8nT to enhance low magnitude anomalies,● zero median/mean traverse is applied in order to balance readings along

each traverse.

(Reference should be made to Appendix B for details on the processing usedfor each survey area).

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Data processing explanation notes:

ClippingClipping replaces the values outside the specified minimum and maximumwith those values. The process is useful for displaying detail, as extremevalues are removed, allowing greyscale shades to be allocated to a narrowerrange of values which improves the definition of anomalies.

Zero Median/Mean TraverseThe median (or mean) of each traverse is calculated ignoring data outside athreshold value, the median (or mean) is then subtracted from the traverse.The process is used to equalise slight differences between the set-up andstability of gradiometer sensors and can remove striping.

2.3.3 An abstraction and interpretation is offered for all geophysical anomalieslocated by the survey. A brief summary of each anomaly, with an appropriatereference number, is set out in list form within the results (Section 3) to allow arapid assessment of features within the survey area. Where furtherinterpretation is possible, or where a number of possible origins should beconsidered, more detailed discussion is set out in Section 4.

2.3.4 The main form of data display used in this report is the greyscale plot.Magnetic data are also displayed as a trace plot. Both 'raw' and 'processed'data have been shown, followed by an abstraction and interpretation plot.

2.3.5 Graphic raster images in bitmap format (.BMP) are initially prepared inArcheoSurveyor. Regardless of survey orientation, data captured along eachtraverse are displayed and processed by ArcheoSurveyor from left to right.Prior to displaying against base mapping, raster graphics require a rotation of206° anticlockwise to restore north to the top of the image. Greyscale imagesare rotated by AutoCAD, traceplots are rotated using ArcheoSurveyor. Rotatedtraceplots are derived from interpolated datasets and can be considered asrepresentative only, as the raw data will have been modified to a minordegree.

2.3.6 The raster images are combined with base mapping using AutoCAD LT 2007,creating DWG file formats. All images are externally referenced to the CADdrawing, in order to maintain good graphical quality. Quality can becompromised by rotation of graphics in order to allow the data to be orientatedwith respect to grid north; this is considered acceptable as the survey resultsare effectively georeferenced allowing relocation of features using GPS,resection method etc.. A digital archive, including raster images, is producedwith this report allowing separate analysis if necessary, see Appendix C below.

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3 RESULTS

3.1 General overview

3.1.1 The detailed magnetic survey was carried out over a total of 1.3ha.Geophysical anomalies located can be generally classified as positive linearand discrete positive responses of archaeological potential, positive linear anddiscrete anomalies of an uncertain origin, negative linear anomalies of anuncertain origin, linear anomalies of an agricultural origin, anomalies with anatural origin, areas of magnetic debris and disturbance, strong discretedipolar anomalies relating to ferrous objects and strong multiple dipolar linearanomalies relating to buried services or pipelines. Anomalies located withinthe survey area have been numbered and will be outlined below withsubsequent discussion in Section 4.

3.1.2 The listing of sub-headings below attempts to define a number of separatecategories that reflect the range and type of features located during thesurvey. A basic explanation of the characteristics of the magnetic anomalies isset out for each category in order to justify interpretation. A basic key isindicated to allow cross-reference to the abstraction and interpretation plot.Sub-headings are then used to group anomalies with similar characteristics foreach survey area.

Anomalies with archaeological potential

Positive anomalies

The category is used where anomalies have the characteristics of a range ofarchaeological features such as pits, ring-ditches, enclosures etc..

Anomalies with an uncertain origin

Positive anomalies Negative anomalies

The category applies to a range of anomalies where there is not enoughevidence to confidently suggest an origin. Anomalies in this category may wellbe related to archaeologically significant features, but equally relativelymodern features, geological/pedological features and agricultural featuresshould be considered.

Anomalies with an agricultural origin

Agricultural anomalies Former ridge and furrow

Where confidence is high that anomalies have been caused by agriculturalfeatures, this category is applied. The anomalies are often linear and form aseries of parallel responses or are parallel to extant land boundaries. Wherethe response is broad, former ridge and furrow is likely; narrow response isoften related to modern ploughing.

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Anomalies with a modern origin

Magnetic disturbanceStrong multiple dipolar linear anomaly - pipeline/service

The magnetic response is often strong and dipolar, indicative of ferrousmaterial and may be associated with extant above surface features such aswire fencing, cables, pylons etc.. Often a significant area around suchfeatures has a strong magnetic flux, which may create magnetic disturbance;such disturbance can effectively obscure low magnitude anomalies if they arepresent.

Anomalies associated with magnetic debris

Magnetic debrisStrong discrete dipolar anomaly

The response often appears as areas containing many small dipolaranomalies that may range from weak to very strong in magnitude. Magneticdebris often occurs where there has been dumping or ground make-up and isrelated to magnetically thermoremnant materials such as brick or tile or othersmall fragments of ferrous material. This type of response is occasionallyassociated with kilns, furnace structures, or hearths and may therefore bearchaeologically significant. It is also possible that the response may becaused by natural material, such as certain gravels and fragments of igneousor metamorphic rock. Strong discrete dipolar anomalies are responses toferrous objects within the topsoil.

3.2 List of anomalies

Anomalies of archaeological potential

(1) – Reversed “L” shaped positive rectilinear anomaly may relate to an enclosure ditch and may be associated with anomaly (2). Although this feature is of archaeological potential, it appears that the cut feature which makes up the long axis is parallel to positive linear anomalies (9), and the shorter axis is parallel with former ridge and furrow.

(2) – Positive rectilinear anomaly forming a reversed “L” shape appears to abut or join anomaly (1) forming an enclosure. The northern extent has not been located.

(3) – Sub-rectilinear anomaly may be bounded on the southern edge by anomalies (8) to form an enclosure.

(4) – Positive curvilinear anomaly appears to cut or be cut by (2) and possibly contain a large pit.

(5) – Cluster of discrete positive anomalies in the northern part of the site appear to

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form a group of pit-like features.

Anomalies with an uncertain origin

(6) – Two parallel positive linear anomalies have the same orientation and spacing as the former ridge and furrow and may be associated. However, it appears that they may have some association with anomaly (3) and therefore their classification is of uncertain origin.

(7) – Two parallel positive linear anomalies close to the south eastern corner of the survey area may relate to cut ditch-like features.

(8) – Two parallel positive linear anomalies in the centre of the site appear to have some association with anomaly (3). However, they have a similar orientation to the former ridge and furrow, and it is possible that they also relate to this type of agricultural activity. .

(9) – Three parallel positive linear anomalies extending across the western half of the survey area with a northwest to southeast orientation. It is possible that they are associated with anomalies (7) in the south of the site.

(10) – Towards the northwestern corner of the site are a group of positive linear, discrete and curvilinear anomalies. It is not possible to determine if they relate to cut features with an archaeological origin.

(11) – Positive linear anomalies may relate to cut features, although of uncertain origin, their archaeological potential should be considered.

(12) – Positive linear anomaly close to the north eastern corner of the site.

(13) – Discrete positive anomalies may indicate pit-like features.

(14) – Negative linear anomalies extending from the north eastern and north western corners of the site appear to converge towards the south western corner. They do not have a similar orientation to any other anomalies including the modern plough trend.

Anomalies with an agricultural origin

(15) – Series of parallel linear anomalies, seen most clearly on the eastern half of the survey area, may continue into the western half. They are between 6m and 7m apart and relate to the former ridge and furrow. Several other linear anomalies within the site, such as (6) and (8), have a similar orientation and may be associated. However, it is possible that the orientation of the ridge and furrow has been influenced by the presence of extant features within the field.

(16) – Linear anomalies caused by modern agricultural activity.

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Anomalies associated with magnetic debris

(17) – Strong discrete dipolar anomalies are a response to ferrous objects within thetopsoil.

Anomalies with a modern origin

(18) – Magnetic disturbance from ferrous material used within nearby fencing.

(19) – Strong multiple dipolar linear anomaly extends along the western edge of the survey area and is a response to a buried service.

Anomalies with a natural origin

(20) – Area of positive response in the north eastern part of the site may relate to an increased depth of topsoil in this part of the field. This may be caused by colluviation although could be related to the construction of the nearby dwellings.

4 DISCUSSION

4.1.1 The survey area appears to contain possibly four rectilinear or curvilinearenclosures although it has not been possible to fully identify their extent.Interpretation has generally been carried out with caution as the site iscrossed by many anomalies that may relate to former cut features. Confidentinterpretation generally requires clear identification of morphologicalcharacteristics, unfortunately, the pattern of anomalies at the site is somewhatincoherent. Anomalies classified as uncertain in origin may relate to featuresof archaeological potential.

4.1.2 Positive magnetic anomalies contrast strongly against the natural soil andsubsoil with peak values over 30nT. The magnitude of the response would beconsistent with a period of intense occupation in close proximity where soilshave become enhanced through burning and biological action. In addition, themineral make-up of the soil is probably particularly favourable to the formationof anthropogenically produced magnetic anomalies.

4.1.3 Cultural material was frequently observed across the site during the survey.Romano-British pottery sherds, tile and stone were identified. The density ofmaterial generally appeared to increase towards the west and tends tocorrelate with anomalies identified as having archaeological potential.

5 CONCLUSION

5.1.1 Magnetometry survey identified strongly contrasting positive linear andcurvilinear anomalies across much of the site. These are likely to beassociated with magnetically enhanced soils forming the fill of former cutfeatures. The pattern of anomalies is often incoherent although four possible

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enclosures were identified.

5.1.2 Given the presence of both Roman and Saxon archaeological sites nearby,and the presence of Roman cultural material within the topsoil across much ofthe site, the enclosures are likely to relate to former settlement and agriculturalactivity. It is likely that features extend beyond the limits of the surveyed areatowards the north and west.

5.1.3 Many anomalies identified as uncertain in origin may be associated withformer cut features. The unclear layout of anomalies possibly indicates activityat the site over a long period. With several anomalies identified as agriculturalin origin, both ridge and furrow and more modern marks, it is possible thatsome earlier features have been disturbed and disentangling those ofarchaeological potential from less important later features is problematic.

6 REFERENCES

British Geological Survey, 1977. Geological Survey Ten Mile Map, SouthSheet, First Edition (Quaternary), Scale 1:625 000.

British Geological Survey, 2001. Solid Geology Map, UK South Sheet,1:625000 scale, 4th edition.

English Heritage, 2008. Geophysical survey in archaeological field evaluation.Research and Professional Service Guideline No.1. 2nd ed. Swindon: EnglishHeritage.

Soil Survey of England and Wales, 1983. Soils of England and Wales, Sheet5 South West England.

The Historic Environment Consultancy, 2009. Archaeological Assessment for Land West of Elm Grove, Ebrington, Chipping Campden, Gloucestershire. Unpublished client report.

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Appendix A – basic principles of magnetic survey

Iron minerals are always present to some degree within the topsoil and enhancementassociated with human activity is related to increases in the level of magnetic susceptibilityand thermoremnant material.

Magnetic susceptibility is an induced magnetism within a material when it is in thepresence of a magnetic field. This can be thought of as effectively permanent due to thepresence of the Earth's magnetic field.

Thermoremnant magnetism occurs when ferrous material is heated beyond a specifictemperature known as the Curie Point. Demagnetisation occurs at this temperature withre-magnetisation by the Earth's magnetic field upon cooling.

Enhancement of magnetic susceptibility can occur in areas subject to burning and complexfermentation processes on biological material; these are frequently associated with humansettlement. Thermoremnant features include ovens, hearths, and kilns. In additionthermoremnant material such as tile and brick may also be associated with human activityand settlement.

Silting and deliberate infilling of ditches and pits with magnetically enhanced soil cancreate an area of enhancement compared with surrounding soils and subsoils into whichthe feature is cut. Mapping enhanced areas will produce linear and discrete anomaliesallowing an assessment and characterisation of hidden subsurface features.

It should be noted that areas of negative enhancement can be produced from materialhaving lower magnetic properties compared to the topsoil. This is common for manysedimentary bedrocks and subsoils which were often used in the construction of banksand walls etc. Mapping these 'negative' anomalies may also reveal archaeologicalfeatures.

Magnetic survey or magnetometry can be carried out using a fluxgate gradiometer andmay be referred to as gradiometry. The gradiometer is a passive instrument consisting oftwo fluxgate sensors mounted vertically 1m apart. The instrument is carried about 30cmabove the ground surface and the upper sensor measures the Earth's magnetic field asdoes the lower sensor but this is influenced to a greater degree by any localised buriedfield. The difference between the two sensors will relate to the strength the magnetic fieldcreated by the buried feature. If no enhanced feature is present the field measured byboth sensors will be similar and the difference close to zero.

There are a number of factors that may affect the magnetic survey and these include soiltype, local geology and previous human activity. Situations arise where magneticdisturbance associated with modern services, metal fencing, dumped waste material etc.,obscures low magnitude fields associated with archaeological features.

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Appendix B – survey and data information

Raw data COMPOSITEFilename: mag-raw.xcp Instrument Type: Grad 601 (Magnetometer )Units: nTSurveyed by: on 17/03/2009Assembled by: on 17/03/2009Direction of 1st Traverse: 0 degCollection Method: ZigZagSensors: 2 @ 1.00 m spacing.Dummy Value: 32702Origin: Zero

DimensionsComposite Size (readings): 720 x 150Survey Size (meters): 180 m x 150 mGrid Size: 30 m x 30 mX Interval: 0.25 mY Interval: 1 m

StatsMax: 10.00Min: -10.00Std Dev: 4.79Mean: -0.72

Processes: 3 1 Base Layer 2 Clip from -30 to 30 3 Clip from -10 to 10

Source Grids: 21 1 Col:0 Row:2 grids\19.xgd 2 Col:0 Row:3 grids\20.xgd 3 Col:0 Row:4 grids\21.xgd 4 Col:1 Row:0 grids\14.xgd 5 Col:1 Row:1 grids\15.xgd 6 Col:1 Row:2 grids\16.xgd 7 Col:1 Row:3 grids\17.xgd 8 Col:1 Row:4 grids\18.xgd 9 Col:2 Row:0 grids\10.xgd 10 Col:2 Row:1 grids\11.xgd 11 Col:2 Row:2 grids\12.xgd 12 Col:2 Row:3 grids\13.xgd 13 Col:3 Row:0 grids\06.xgd 14 Col:3 Row:1 grids\07.xgd 15 Col:3 Row:2 grids\08.xgd

16 Col:3 Row:3 grids\09.xgd 17 Col:4 Row:0 grids\03.xgd 18 Col:4 Row:1 grids\04.xgd 19 Col:4 Row:2 grids\05.xgd 20 Col:5 Row:1 grids\01.xgd 21 Col:5 Row:2 grids\02.xgd

Processed data

COMPOSITEFilename: mag-proc.xcp

StatsMax: 8.00Min: -8.00Std Dev: 4.11Mean: 0.05

Processes: 4 1 Base Layer 2 Clip from -30 to 30 3 DeStripe Median Traverse: Grids: All 4 Clip from -8 to 8

Source Grids: 21 1 Col:0 Row:2 grids\19.xgd 2 Col:0 Row:3 grids\20.xgd 3 Col:0 Row:4 grids\21.xgd 4 Col:1 Row:0 grids\14.xgd 5 Col:1 Row:1 grids\15.xgd 6 Col:1 Row:2 grids\16.xgd 7 Col:1 Row:3 grids\17.xgd 8 Col:1 Row:4 grids\18.xgd 9 Col:2 Row:0 grids\10.xgd 10 Col:2 Row:1 grids\11.xgd 11 Col:2 Row:2 grids\12.xgd 12 Col:2 Row:3 grids\13.xgd 13 Col:3 Row:0 grids\06.xgd 14 Col:3 Row:1 grids\07.xgd 15 Col:3 Row:2 grids\08.xgd 16 Col:3 Row:3 grids\09.xgd 17 Col:4 Row:0 grids\03.xgd 18 Col:4 Row:1 grids\04.xgd 19 Col:4 Row:2 grids\05.xgd 20 Col:5 Row:1 grids\01.xgd 21 Col:5 Row:2 grids\02.xgd

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Appendix C – digital archive

Survey results are produced in hardcopy using A4 for text and A3 for plots (allplots are scaled for A3). In addition digital data created during the survey aresupplied on CD. Further information on the production of the report and thedigital formats involved in its creation are set out below.

This report has been prepared using the following software on a Windows XPplatform:

● ArcheoSurveyor version 2.3.1.1 (geophysical data analysis),● AutoCAD LT 2007 (report figures),● OpenOffice.org 3.0.0 Writer (document text),● PDF Creator version 0.9 (PDF archive).

Digital data are supplied on CD ROM which includes the following files:

● ArcheoSurveyor grid and composite files for all geophysical data,● CSV files for raw and processed composites,● geophysical composite file graphics as Bitmap images,● AutoCAD DWG files in 2000 and 2007 versions,● report text as OpenOffice.org ODT file,● report text as Word 2000 doc file,● report text as rich text format (RTF),● report text as PDF,● PDFs of all figures,● photographic record in JPEG format.

The CD ROM structure is formed from a tree of directories under the title J271Ebrington – CD. Directory titles include Data, Documentation, CAD, PDFsand Photos. Multiple directories exist under Data and hold Grid, Compositeand Graphic files with CSV composite data held in Export.

The CAD file contains externally referenced graphics that may be rotated , see2.3.5, with separate A3 size layouts for each figure. Layouts are fixed usingfrozen layers and named views allowing straightforward plotting or analysis onscreen. (Note – CAD files are prepared using AutoCAD's e Transmit functionto produce a directory containing the digital drawing along with any externallyreferenced graphics which may need reloading).

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Documents

Land West of Elm Grove Ebrington Gloucestershire2.3 Data processing and presentation 2.3.1 Magnetometry data downloaded from the Grad 601-2 data logger are analysed and processed in