Evaluation of the application of geophysical survey techniques in the gardens of Wortley Hall, South Yorkshire, Spring 2009

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Evaluation of the application of geophysical survey techniques

in the gardens of Wortley Hall, South Yorkshire, Spring 2009

Evaluation report prepared by:

Colin Merrony

Department of Archaeology

University of Sheffield

Northgate House

West Street

Sheffield

S1 4ET



Contents

1. Summary introduction

2. Location, geology, topography

3. Historical and archaeological background

4. Methodology

5. Results

6. Discussion and conclusions

7. Recommendations

8. Acknowledgements

9. Bibliography

Appendix 1: Technical information



Illustrations

1. Location of survey areas

2. View of area A from the east

3. View of area B from the south-east

4. Greyscale plot of the results of the resistivity survey of area A

5. Greyscale plot of the results of the resistivity survey of area B

6. Photographs of the cultivation within survey area B

7. Greyscale plot of the results of the magnetometer survey of area B

8. Greyscale plot of the results of the magnetometer survey of area B with significant features highlighted

9. Plan of the survey areas with the greyscale plots from the resistivity surveys overlaid in order to allow

the significance of the positions of features defined to be shown

10. Plan of the survey areas with the greyscale plots from the magnetometer survey overlaid in order to

allow the significance of the positions of features defined to be shown

11. Photograph of the northern half of the walled garden showing the different character of the cultivation

in this area



Evaluation of the application of geophysical surveying in the gardens of Wortley Hall, South

Yorkshire, Spring 2009

_________________________________________________________________________________________

Report prepared by: Colin Merrony

Fieldwork conducted: March/April 2009

_________________________________________________________________________________________

Summary

Two areas of archaeological geophysical survey were undertaken in the grounds of Wortley Hall

during March and April 2009 in order to investigate the potential effectiveness of the techniques used

for the exploration of archaeological deposits and structures within this historic garden. One area was

within the Walled Garden and the other was on an area of lawn close to the entrance to the Stable

Block. The work undertaken included surveys with both magnetometery and resistivity surveys

conducted by students on the M.A. in Landscape Archaeology at the University of Sheffield at theinvitation of the staff of the current community archaeology programme based at the Hall.

The surveys successfully produced good quality geophysical data and located features which appear

likely to be associated with the historic garden. These results demonstrate that geophysical survey

methods are highly likely to be successful in exploring this historic garden and provide a basis from

which a future programme of fieldwork may be planned.

Altogether a total of c. 1,600 square metres were surveyed with magnetometry and/or resistivity.



Location, geology and topography

The village of Wortley (SK308995) is situated on the Coal Measure Group of Carboniferous

sedimentary rocks. The village is approximately 12 kilometres north-north-west of Sheffield and

occupies a hilltop location (at around 220m.A.O.D.) along the ridge which overlooks the valley of the

River Don to the west. Wortley Hall lies approximately 0.5 kms. to the east of the village on the east

facing flank of this ridge (at about 200m.A.O.D.) overlooking a small valley which runs down towardsWorsborough to the north-east. The two areas surveyed lie to the west of the Hall in and adjacent to the

large walled kitchen garden (Figure 1). They were designated Area A (the smaller area adjacent to the

stable block) and Area B (within the walled kitchen garden).

Figure 1: Location of Wortley Hall survey areas (© Crown Copyright/database right 2009. An Ordnance Survey/

(Datacentre) supplied service)



Historical and archaeological background

A Deer Park was enclosed around 1510 and in use until 1649 even though a hall was built on the site

of the present hall during the mid 16th century. The hall as we see it today was mainly developed in the

18th century with a south front built in 1742-46 by Giacomo Leoni for Edward Wortley-Montagu

(d1761); an east wing 1757-61 by Matthew Brettingham and additions by John Platt for Lady Bute

(d1784) during 1784-88 (which were completed for James Archibald Stuart Wortley under guidance of

John Carr of York). The hall is a grade 2* listed building. The Park was landscaped circa 1800 andcontains mid 19th century gardens and pleasure grounds. Only a fraction of the once extensive park is

now still in existence as the present gardens of Wortley Hall, as much has been returned to agriculture

(Hey, 1975). However the particularly large and fine walled kitchen garden survives intact and

although many of its walls are in poor repair and in need of urgent attention, the extraordinarily

extensive hot wall system is still visible.

Methodology

In both areas surveyed, a preliminary walk over survey was conducted to see if any earthwork features

were visible. In neither case were significant features identified. The geophysical surveys of each areawere then conducted using a grid of 20 metre squares oriented on baselines which ran along

convenient boundaries. In the case of area A the baseline was placed along the edge of the path which

approaches the arch into the stable block area (see figure 2). For area B the baseline was set up parallel

(and approximately 1 metre south of) the central wall of the walled garden beginning just west of the

gap in this wall which provides access between the two halves of the walled garden (see figure 1).

Area A was surveyed first and lay on a triangular area of lawn in front of northern half of the building

that provides an entrance to the stable block/walled garden area. This area was covered with a single

20 metre square. Area B, which is larger comprising 2 full and 2 half 20 metre squares lay within the

western portion of the southern half of the walled garden. While this area is partially cultivated beds,

partially grass and partially fruit trees the area surveyed was the most accessible part of the southernhalf of the walled garden. The extreme western end of the southern half of the walled garden is fenced

off while to the south of the cultivated area stands a large tunnel greenhouse. The northern part of the

walled garden was not surveyed at this time as the whole of this area is under cultivation.

The grid squares were laid out in advance of the surveys. Area A was covered by resistivity survey

only, however the survey was conducted twice with differing mobile probe separation distances. The

first survey was conducted with a mobile probe separation of 0.5m. giving a depth penetration of

approximately 0.75m. The same area was then resurveyed with a mobile probe separation of 0.25m.

giving a depth penetration of 0.35-0.40m. The whole of Area B was covered by a resistivity survey

with the northern half also being covered by a magnetometer survey using the same grid (for brief

descriptions of the principles upon which these techniques are based see Appendix 1 and for more

information see Gaffney & Gater, 2003). Temporary marked lines were used to mark the data

collection lines during each survey. The magnetometer survey was conducted using a Geoscan FM256

Fluxgate Gradiometer and the resistivity survey was conducted using a Geoscan RM15 Resistivity

Meter. The data recovered was processed using GEOPLOT software. Further details of the instrument

and processing are given in Appendix 1 and the raw data recovered is given in Appendix 2.

The sampling interval for the resistivity survey in area A was 1.0 m. along traverses which were spaced

one metre apart. This resulted in 400 data points for the 20 metre square for each survey pass. For area

B the sampling interval for the resistivity survey was also 1.0m. along traverses 1 metre apart, however

the magnetometer survey used a sample spacing of 0.25m. along traverses 1 m. apart. In area B a totalarea of 1200 m2 was surveyed, resulting in a total of 1200 resistivity data points and 2400

magnetometer data points. The software then interpolated readings in between each traverse to create

a total of 6400 data points for each 20 metre square, giving a pixel size of 0.25 m. on the final output.



Figure 2: View of area A from the east. The survey area is the triangle of lawn in the centre of the

photograph. The entrance to the stable block area is through the arch visible on the left and theentrance to the walled garden can be seen through the arch.

Figure 3: View of area B from the south-east. Area B covered the whole area from just to the left of

the entrance to the other half of the walled garden (this entrance is the gap in the wall visible on the

right of the photograph) up to the fenced area (where the land rover is parked left of centre). Note the build up of waste material against the wall on the left of the photograph. A smaller build up occurs

against the far wall.



The vegetation cover within area A was very short grass as this was a closely cut lawn. In area B the

vegetation cover varied between longer grass (this area is not a formal lawn and while mown, this is

clearly done less frequently), some cultivated beds mainly of bare soil but which also contained new

plantings of strawberries, rhubarb and some ornamental plants and some free standing fruit trees in the

grassed area towards the western end. The weather throughout the survey was bright with little wind.

There was some light rain during the period of the survey. However the weather conditions were very

suitable for geophysical survey.

Results

The data recovered has been processed and converted into a series of ‘greyscale’ plots which allow

patterns within the data to be discerned (see appendix 1 for information relating to greyscale plots).

The individual greyscale plots for each area are presented separately in figures 4 to 6. The description

of the results obtained and the following discussion will primarily refer to these figures. However there

is also a figure where the greyscale plots have been overlaid onto the Ordnance Survey map for the

area which allows the significance of the location of defined geophysical features to be assessed Figure

7).

The resistivity results are of very good quality with a consistent background showing the sort of

variation typically associated with the Coal Measures. While few archaeological features have been

defined the results obtained do provide a basis upon which it is possible to assess the potential

effectiveness of further geophysical survey within the gardens.

Figure 4: Greyscale plots from the survey of area A. The results represent a depth penetration of

approximately 0.75m. (left) and 0.35-0.40m. (right).

As can be seen in figure 4 the results obtained from both surveys of area A are very similar. In both

plots the edges of the survey area have produced lower resistance readings while the centre of the area

produces an indistinct area of much higher readings. The range of values in both cases is very large

with significantly high readings being obtained in the central area. These results are compatible with a

thin topsoil layer overlying stone rubble or perhaps bedrock/weathered bedrock. It is likely from these

results that the whole of area A is underlain by stone at significantly less than 35 cms. depth. The lower

resistance readings obtained from the margins of the survey area probably result from water running

off the surrounding tarmac road/paths and the adjacent building onto this grassed area. The only area

which does not exhibit this ‘edge effect’ is the eastern corner and in this point the survey did not reachthe very edge of the grassed area due to the presence of a mature conifer (see figure 3 – foreground).



A single resistivity survey was conducted in area B with a 0.5m. mobile probe separation (giving a

depth penetration of approximately 0.75m.). As can be seen in figure 5 area B provided results with

significant variation which may be due to either buried features or aspects of the current cultivation

system within the walled garden. The highest readings obtained are those along the southern margin of

the survey area and these coincide with a spread of rubble and other debris along the side of the wall

that runs parallel to the edge of the survey area (this wall is the southern external wall of the walled

garden). This spread of material can be seen in the left foreground of figure 3. It is very probable that

these high resistance readings are caused by this spread of building material and other debris.

Figure 5: Greyscale plot of the resistivity results from area B.

The range of readings within survey area B is narrower than in area A. This is not surprising within an

area such as a walled garden as this is compatible with a deeper soil profile which would provide a

‘smoother’ background for a survey than an area underlain by a deep layer of rubble or in which

bedrock is relatively near the surface.

In the main body of the survey area, however, are a series of linear low resistance features runningsouth-east north-west across the survey area. These features are 1-2 metes wide and approximately 5

metes apart and running perpendicular to the walls of the walled garden. It is very likely that

archaeological features such as paths, structures and planting beds within an area such as an historic



walled garden will be oriented either parallel with or perpendicular to the enclosing and dividing main

walls of the walled garden as these kitchen garden areas are designed and managed to be efficient food

and other produce production areas. Cultivation in historic kitchen gardens is a very regimented and

carefully controlled process with regular arrangements and strict cropping and management regimes.

Consequently these low resistance features may be related to buried archaeological deposits. However,

a related but alternative source is perhaps more likely for these particular features. As can be seen in

figure 6 the walled garden at Wortley is currently cultivated (by arrangement with Heeley City Farm).

While the current management regime is less intensive than would have been the case in the 18th

/19th

century it shares the same logical arrangement with beds and structures aligned with or perpendicular

to the walls of the walled garden.

Figure 6: The photograph on the left shows the area of survey area B (viewed from the gateway between the two halves of the walled garden) which is currently partly under grass but with planting

beds and fruit trees in rows perpendicular to the walls of the walled garden. The photograph on the

right shows one of these planting beds (in this case planted up with strawberries). These planting beds

have clearly been recently deeply dug and newly planted up.

The current series of planting beds are approximately 5 metres apart and 1 metre wide and in all cases

except 1 (the easternmost of the beds which contains mature ornamental plants) have recently been

deeply dug and then planted with new stock of plants such as strawberries or rhubarb. This recent

cultivation of the topsoil (perhaps with the incorporation of significant amounts of organic material

prior to the planting) may readily alter the moisture holding properties of these strips of land. It is very

likely that the low resistance features visible on the greyscale plot are the product of this current

cultivation and not related to any buried archaeological features. This could be confirmed by a

measured survey of the area to overlie the precise positions of these features on the greyscale plot.

However, it should be noted that if these beds are left planted for a few years then this effect is likely

to reduce and so it may be that if the planting in these beds is maintained and not renewed then a

resurvey in 2 or 3 years time may be substantially less affected by this phenomenon. It should also be

noted that the apparent misalignment in these linear features (with a ‘kink’ near the centre of the

survey area) is caused by a slight misalignment of the two halves of the survey grid which were

surveyed on two separate days and cannot be taken as a factor with which to challenge the correlation

between the low resistance features and the current planting beds.

The northern half of the survey area was also covered by a magnetometer survey and the results from

this survey can be seen in figure 7. The value of a magnetometer survey in this area was initially



doubted as areas such as kitchen gardens have been the focus of intense activity in the past and can

contain significant levels of iron-rich (nails, pieces of wire, broken tools) and burnt (ash from hearths

in nearby buildings and the material left over from bonfires) debris, which may cause a very ‘noisy’

background. It was felt that this would be further compounded by the presence of small fruit trees and

some areas of longer vegetation which would offer a physical barrier for the maintenance of a

consistent orientation of the magnetometer. However as this was a trial survey and also a training

opportunity for students an area was surveyed with magnetometry. The trees and longer vegetation did

make the completion of the magnetometer survey more challenging than would be considered ideal.However as can be seen in figure 7 the results were not significantly affected and the background noise

levels are, in general, surprisingly low.

Figure 7: Greyscale plot of the results from the magnetometer plot of the northern half of area B.

There are clearly two areas affected by metal (iron-rich debris). The largest of these areas is in the

northern corner adjacent to the gateway between the two halves of the walled garden. The clear cluster

of dipole features here is typical of a series of pieces of iron on or near the surface. As this access route

between the two halves of the walled garden would have been a major focus for movement and

activity it is not surprising that this area has a higher level of discarded material. The other anomaly

which is typical of metal debris is the negative anomaly on the south-east margin of the area covered

by this survey. This is compatible with a single significant piece of iron. There were several very small‘spikes’ in the readings across the survey area which will have been caused by very small pieces of

iron (such as individual nails near or on the surface). These ‘spikes’ have been filtered out during the

data processing.

Overall the main body of the survey has a fairly low level of variation suggesting that magnetometer

survey within the walled garden may be more effective than initially estimated. There are some weak

magnetic features running south-east to north-west across the survey area which may be related to the

cultivation of the area. However the magnetometer survey is clearly unaffected by the planting beds

which had such a significant impact on the resistivity survey.

One interesting feature does emerge from the results of this survey. There is a slightly curving, linear,weakly positively magnetic anomaly running south-west to north-east across the whole of the survey

area. This feature is running roughly parallel to (although it does appear to curve slightly so it is not

truly parallel to) the central wall of the walled garden which forms the north-western boundary of area



B. This linear feature is approximately 6 metres from this wall. The feature has been highlighted in red

in figure 8.

Within a walled garden it would be expected that geophysical survey may produce evidence of features

such as paths and possibly garden structures such as lean-to buildings built against the main walls.

These sorts of features have been found previously in geophysical surveys in historic gardens within

this region (for example Chatsworth and Brodsworth, see Woudstra, Merrony and Klemperer, 2005

and Merrony et al, 2004). The arrangement of such features is usually heavily correlated with mainstructural features such as the walls of a walled garden. It is to be expected that paths would run close

and parallel to main walls or cross areas by running perpendicular to the main walls. However the

linear feature in area B is several metres from the central wall and clearly has a slight curve. This and

the fact that it was not detected in the resistivity survey supports the interpretation that this feature

does not represent a path. It is more likely that this feature is produced by a pipe or conduit buried at or

below 0.75 metres below the current ground surface. This may be a drain or it may be pipe. The weak

nature of the magnetic anomaly suggests that this must be produced by a weakly magnetic material

such as a ceramic pipe or perhaps a cut holding a lead pipe. The readings are too weak for an iron pipe

or electricity cable to be a likely source for this feature.

Figure 8: The main area of disturbed readings caused by discarded iron is highlighted in blue at the

top of the plot. The slightly curving linear feature running almost parallel to the central wall of thewalled garden is highlighted in red.



Figure 9: The greyscale plots of the results from the resistivity surveys overlain on the map of the site

so the significance of the location of features can be more easily determined (© Crown Copyright/database

right 2009. An Ordnance Survey/ (Datacentre) supplied service).

Figure 10: The greyscale plots of the results from the magnetometer survey overlain on the map of the

site so the significance of the location of features can be more easily determined (© Crown

Copyright/database right 2009. An Ordnance Survey/ (Datacentre) supplied service).



Discussion and conclusions

The results from these preliminary surveys have provided good quality data and strongly suggest that

geophysical survey can be successfully applied in a variety of locations within the gardens of Wortley

Hall. In particular the magnetometer results are more effective than had initially been expected.

The results from the walled garden do not provide the very clear results obtained in other walledgardens such as Brodsworth and clearly the current method of cultivation in area B causes some

problems for geophysical survey. However most of the walled garden is a large open cultivated area

(see figure 11) and this would therefore not present the same problems of interference as the area is

consistent. This area is intensively cropped in the summer with a lower level of activity in the winter.

Consequently if an appropriate time could be found when it would be possible to conduct a survey

over all or most of this area (winter?) then it is to be expected that useful results could be recovered

from this area.

Figure 11: View of the northern half of the walled garden showing that cultivation here is in the form

of two large open areas (separated by a central grass track lined by fruit trees - visible in the centre of

the photo). This form of cultivation would probably yield more effective geophysical survey results

(particularly resistivity)

The results also suggest that the ornamental garden should produce good results. Here the limitation

will be the area available for survey. The area has many paths and mature shrub/tree borders. However

there are significant areas of lawn and particularly in the area of the larger lawns useful results could

be obtained. There is every reason to expect that if the foundations of earlier structures or features suchas paths do lie in these areas then these structures and features would be definable by geophysical

survey.



Recommendations

Bearing in mind the findings from this preliminary geophysical survey it is clear that useful data could

be obtained from the gardens of Wortley Hall if further geophysical surveys were conducted. It should

be strongly recommended that significant further survey be conducted if suitable permission can be

obtained. All the larger areas of lawn could be surveyed at almost any point of time during the year (avoiding extreme dry or wet conditions) using both resistivity and magnetometry. In addition it would

be very useful to complete an extensive survey (resistivity and magnetometry) within the walled

garden if a time can be found when the area can be accessed without disrupting the cultivation, most

likely a point in the late winter. This would be a matter for careful timing in order to remove any

significant impact on the crops.

Acknowledgements

My thanks go to Jenny Marchant and Dan Ratcliffe of the Wortley Walled Garden Heritage Project for

the invitation to undertake geophysical survey work in the gardens of Wortley Hall and to the

management committee for providing permission for the work to go ahead. The work was undertaken

by Peter Cox, Clare Nowell, Peter Townend, Andrew Poyer and Luis Martinez-Vazquez; all students

on the M.A. in Landscape Archaeology at the University of Sheffield. We are also grateful for the help

and kind words from the gardening team including Marc Mallender and Rachel Parkin.

Bibliography

Gaffney, C. & Gater, J. 2003 Revealing the buried past: geophysics for archaeologists (Stroud:

Tempus)

Hey, D. 1975 The Parks at Tankersley and Wortley (Yorkshire Archaeological Journal 47: 109-

119)

Merrony, C.J.N.; Klemperer, M.P.; Shone, R.; Garnham, M. and Cusworth, M. 2004 Geophysical

surveys to evaluate the survival of Post-Medieval archaeological features in the walled garden

at Brodsworth and adjacent to Elm Farm, Pickburn, South Yorkshire. (Unpublished interimreport of the Brodsworth Community Archaeology Project, University of Sheffield for the

Brodsworth Estate Trustees and the South Yorkshire Archaeology Service)

Woudstra, J.; Merrony,C.J.N. and Klemperer, M.P 2005 The Great Parterre at Chatsworth: refining

non-invasive archaeological methods as investigation techniques (Garden History 32:1: 49-67)



APPENDIX 1

TECHNICAL INFORMATION

A1.1 Instrumentation

Magnetometer:- Geoscan FM256

Sampling Interval:- 0. 25 metre

The Geoscan FM256 is a Flux-gate Gradiometer that utilises two sensors to measure external magneticfields. The upper sensor is positioned to detect the earth's magnetic field, while the lower sensor detects the earth's magnetic field plus any other magnetic field resulting from below ground features.The two measurements are compared so that the effect of the earth's magnetic field can be removed.The strength of any other magnetic field present is then recorded. The instrument is carried so that onesensor is positioned vertically above the other and measurements are taken at one metre intervals

across a fixed grid.

There are two main mechanisms by which archaeological deposits become able to possess a magneticfield and therefore become detectable by magnetometer survey. The first of these is ThermoremanentMagnetisation. This results when a material containing iron oxide particles (i.e. virtually any soil or subsoil) is heated up to above the Curie point of the iron oxide particles it contains (650 degreesCentigrade or more). On heating the iron oxide particles demagnetise. When the material cools downagain the iron oxide particles remagnetise as far as possible preferentially aligned with the earth'smagnetic field. This alignment of the magnetic fields of the iron oxide particles produces aneffectively fixed permanent magnetic field for the material as a whole. This magnetic field can bedetected by a magnetometer survey. The second mechanism is that of Magnetic Susceptibility. This isthe ability of a material to become magnetised when placed in a magnetic field. Iron oxides are highlyMagnetically Susceptible, although the precise level of this depends on the form of the oxide.Consequently increasing the concentration of iron oxide or changing the form of the iron oxide

particles will make a deposit more Magnetically Susceptible. If this deposit is placed within amagnetic field a greater magnetic field will result. Fortunately all archaeological deposits, along witheverything else on the Earth, are within the Earth's Magnetic Field at all times and the resultingmagnetic fields can be detected by a magnetometer survey.

Resistance Meter:- Geoscan RM15

Probe Array:- Twin-Probe (mobile probe spacing 0.5 metre)

Sampling Interval:- 1.0 metre

The Geoscan RM15 is an instrument that measures the electrical resistance of soils and sediments.Four electrodes are employed; two current probes (that pass the electric current) and two potential

probes (that measure the resistance to the passage of that current). These four electrodes may bearranged in various ways. Depending on the arrangement, measurements of similar volumes of sediments can be obtained and the amount measured may be used to calculate a value of resistivity of the sediments. In the Twin-Probe arrangement the electrodes are 'paired' (a current probe with a

potential probe), with one of the pairs remaining in a fixed position whilst the other pair is movedthereby measuring the resistivity variations across a fixed grid. The fixed grid is sampled at one metreintervals. With the spacing between the mobile probes set at 0.5 metre the resistance method has adepth penetration of approximately 0.75 metre and with the probes set at 0.25 metre the depth

penetration will be 0.35-0.40 metre, although the nature of the overburden, underlying geology and

soil moisture levels will cause variations in this figure (the mobile probe spacing can be altered further to give different more depth penetration values).

The resistance to the passage of an electric current through a soil or sediment is primarily related tomoisture content. Electric current passes more easily through moist deposits than dry. Consequently



resistance survey is particularly suited to the definition of buried archaeological remains that are theresult of past human actions that have altered the ability of the deposits to hold moisture. Thefoundations of a stone or baked block wall hold considerably less moisture than the organic-rich fill of a ditch or pit. Consequently the resistance values of a pit or ditch may be expected to be significantlylower than those of a wall. Complete waterlogging or desiccation of soils and sediments can causethese differences to become (temporarily) undetectable and so weather conditions and general soilmoisture levels must be noted.

Data processing:-

The magnetometer and resistivity data used for this report was processed using GEOPLOT software(from Geoscan Research Ltd, Bradford) initially run on a Toshiba Satellite 320 CDS laptopmicrocomputer and then finally processed on a Viglen Contender Pentium microcomputer. Graphicimages were prepared in Adobe Photoshop (from Adobe Systems Inc., San Jose).

A1.2 Display Options

Below is a description of the display options used in this report. Unless specified in the text nofiltering or smoothing will have been used to enhance the data. Any 'smoothing' on plots shown in thisreport is simply a process of interpolating a median measurement in between each pair of measurements across the plot, thus creating a smaller unit size.

Dot-Density: in this form of graphical display of the numerical data minimum and maximum cut-off levels are chosen (this is done before the data is processed for this display). Any value below theminimum cut-off level will appear blank (white), whilst any value above the maximum cut-off levelwill appear black. The values that lie between the two cut-off levels are each assigned a specificnumber of dots depending on their relative position between the two cut-off levels. Each reading isallocated a unique area dependant on its position on the fixed survey grid. Within this unique area thenumber of dots allocated to that specific reading are randomly placed.

Colour plot: A given range of readings is divided into a set number of bands (similar to Dot-Density

above). These bands have predefined shades of various colours, allowing areas of anomalous readingsto be highlighted as regions of particular colours.

Grey scale: Similar to Colour plot (above) but the bands are allocated shades of grey thus allowingareas of anomalous readings to be highlighted as light and dark areas on the printout.

Line graph: This display converts data values the Y axis into a series of line graphs, one for each lineof data which are then stacked on top of each other. The resulting view gives an apparent oblique viewof the three-dimensional surface ‘created’ by the stacking of the individual line graphs.

Evaluation of the application of geophysical survey techniques in the gardens of Wortley Hall, South Yorkshire, Spring 2009

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