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DART progress report July 2011

Sensor Arrays and Surveys

The past 6 months have represented a major milestone for the project. We have installed both

sensor arrays at RAC and one sensor array at Diddington the final array will be installed in late July.The regular monitoring surveys have started. At present the geophysical surveys geotechnical

sampling and spectro-radiometry have a monthly baseline interval. Further, two weekly, spectro-

radiometry surveys are taken at Diddington and will continue until the crop is harvested. In addition

we have been in communication with the farmers and will attempt to take specific geophysical

measurements to evaluate the impact of ploughing and harrowing on signal attenuation. The

experience of doing this work has led to the consolidation of methodology.

Aerial Surveys

Two local aerial archaeologists, Robert Bewley (Cirencester) and Rog Palmer (Diddington) are

undertaking regular flights over both sites. These photographs can be found on the DART website:

http://dartproject.info/WPBlog/?page_id=63. On the 27th

June 2011 the Environment Agency haveundertook a CASI hyperspectral, LiDAR and vertical photograph survey. These are collected at a

ground resolution of 1m, 1m and 0.25m respectively. The LiDAR and vertical photography cover

approximately 20km2

around each site and the CASI covers approximately 3km2. In addition we put

in a bespoke application to NERCs Airborne Remote Sensing Facility for hyperspectral flights after

observing the impact that the 1 in 100 years drought event was having on cropmarks at Diddington.

This was submitted on Friday 10th

June, approved on Monday 13th

June and flown on Tuesday 14th

June. Many thanks to NERC for this flight. Concurrent spectro-radiometry readings were taken for

both the CASE and NERC ARSF flights to compensate for atmospheric effects. NERC, Cambridgeshire

County Council and DART will produce a press release on these flights.

WorkshopOn the 27th April the first DART community workshop was held at Leeds University. Given the time

of year it was well attended with 30 community participants and the DART team bringing this up to a

total of 40 people. We managed to get a good cross-section of academics, curators, practitioners

and community groups as can be seen from the delegate breakdown below. The day is summarised

in a blog post http://dartproject.info/WPBlog/?p=1253.

Partnerships

Van Walt Ltd., Allied Associates Geophysical Ltd., Leica Geosystems have all continued to offer

support. Van Walt will be installing one of their TDR probes for comparative analysis at the next

Diddington installation. Allied Associates have provided geophysical equipment. Leica Geosystems

have provided access to both RTK-GPS and their SmartNET service. Many thanks to all these

organisations for their support.

Future work

From here on in DART will become very data intensive. We need to put in place effective back-end

infrastructure to host and share large data and to find appropriate mechanisms to place this data in

the public domain and present (or visualize) the data. The ARSF grant for 2012 will need submitting

in October.

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Robert Fry: Geophysics

Preliminary Geophysics at Sites

Fluxgate Gradiometer surveys were undertaken at Harnhill and Diddington. These were used at the

main location maps for the TDR placement on site. The survey was conducted by RF and DS during

January and February, with associated reports written up for the landowners and DART principal

investigators. From the successful results of the surveys, coring locations were selected in order to

characterise the ditch locations (coring completed by KW).

FlashRes64Resistivity Imaging Equipment

The new FlashRes resistivity Imaging Equipment has currently been on loan from Allied Associates,

and tested on a number of different sites. I am now confident the instrument works sufficiently and

the University of Bradford (UoB) are purchasing the equipment to be used and to constitute the

main focus of the monthly surveys and indeed, the PhD. The importance of the high-definition

results from the instrument should really help with characterising the seasonal moisture contrasts in

the soil. To help disseminate and understand the data further, I am currently attempting to write a

Python program which extracts specific arrays from the FlashRes data.

EM CMD MiniExplorer equipment

After the DART workshop, it was noted that testing Electro Magnetic (EM) survey would be of

interest to commercial interested parties. Thanks to Allied Associates again, UoB have been lent a

new EM instrument which could revolutionise the use of this method for archaeological prospecting.

After successful surveys at Quarry Field (Harnhill) it is hoped that a future lending program might be

arranged to collect more EM data over the fields.

Excavation and Installation

After successfully locating the sites through geophysical survey and coring, 3 TDR boxes at

Cirencester and 1 at Diddington have been installed. Soil samples taken from all fields.

Publications / Dissemination

y AARG News: DART students AARG conference summaryy ISAP News: The DART project a roadmap for the 21st centuryy RSPSoc News: DART project updatey ISAP Conference: FlashRes64 - extended abstractandDART project extended abstract

Future work

I am about to start undertaking the monthly survey of the fields. This will generally be in the last

week of the selected month (where logistically viable) and will involve, survey with a multiplexed

resistance meter (at Twin probe spacings of 0.25m / 0.5m / 0.75m and 1m), the FlashRes ERI system,

as well as EM survey when available. (Dan will also be providing GPR data from each site eachmonth).

Foreseeable issues

Not so much an issue yet, but I am currently attempting to work out how to correctly and effectively

compare and analyse the data I collect.

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Dan Boddice and Laura Pring: Geotechnics

TDR installation

The three TDR monitoring stations at the RAC (two in quarryfields, one in cherry copse) have been

activated, and have been collecting data since May. Large scale analysis of this data in its entirety is

currently impossible, as each waveform takes a considerable amount of time to locate the start and

end reflection points. However, a small sample of the data has been analysed, to check viability, the

results of which were positive. After the final installations have been completed, a script to

automatically locate the reflection points will be developed. This will dramatically improve analysis

time.

TDR logging issues

Some outstanding issues exist with the data collection, with the principle problem being that the CF

cards used to store the data are filling up at a much quicker rate than expected (around 2 weeks).

Contact has been made with Campbell scientific on this issue, and they are currently investigating.

The latest thinking is that the table fill times being reported by loggernet are not accurate and

running a program in the lab may help us to determine accurate table fill times. Investigations into

uploading the data to an ftp server using the GSM modems are also being conducted, as this would

produce a pseudo-live data feed, from which any problems or data skips could quickly be identified,

and reduce the CF cards role to backup.

Weather station installation

Three weather stations have currently been installed, two at the RAC and another at the pasture

field at Diddington. A final station will be installed at Diddington in July. All three of these have been

observed to be collecting and recording data at regular intervals appropriately.

Weather logging issues

Some of the measurements are not fully explained by the software or manual, and we are currently

in contact with Prodata (who sold us the weather stations) and Davis (the manufacturer) to obtain

information on how some of the derived measurements such as rain rate are calculated, in order to

better understand the data and use it more effectively.

Future work

In the forthcoming months of the project, we will be undertaking a number of different activities

y Solve the data issues mentioned above on the TDR sensorsy Finish and install the remaining two sensors at the clay site at Diddingtony Develop a script to computer analyse the waveforms from the TDR to process the data

quickly

y Source a vibracorer and develop a methodology on frequency and locations for coringy Begin geotechnical laboratory tests on the soil samples from the two sites

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David Stott: Spectral analyses

Spectro-radiometry survey

Since the last meeting we have recorded three spectro-radiometry transects at Diddington on a two

week interval. Diddington has become the focus for this work as it has had both EAGLE, HAWK and

CASI hyperspectral (pre and post a rain event), it is also logistically easier to get to Diddington from

Leeds. This is essential as we are weather dependant. The methodology for this work has been

refined to enable the lab work to be conducted at or near site using a portable enclosure and sun

emulating lamps. This reduces the risk that the vegetation samples will degrade after being taken,

and reduces dependency on the weather for field measurements. Vegetation height and relative

chlorophyll content are also recorded for each spectro-radiometry transect.

In addition to the site work additional spectro-radiometry reading are being recorded of the wheat

plants being subjected to lab based stress testing in Leeds (Plant Biology).

Excavation and Probe installation

The excavations provided a detailed understanding of the nature of the three features identified so

far. These are:

y A relict field boundary and drain in clay (Quarry Field at Harnhill)y A substantial relict field boundary cut into limestone bedrock (Cherry Copse at Harnhill)y A prehistoric ditch in gravel, sealed by an alluvial deposit (the pasture field at Diddington)

That these features are all so different is encouraging, as they will surely provide a wide range of

responses to changing conditions.

The monthly surveys

The monthly surveys began in the last week of June 2011. During these the spectro-radiometry and

geophysical data will be co-collected. The first survey provided valuable insights as to how we can

work together most efficiently.

Aerial data

Ground-based spectro-radiometry readings were co-collected during the NERC and Environment

Agency hyperspectral flights. This will allow us to correct for atmospheric attenuation. The oblique

aerial photography provided by Bob Bewley and Rog Palmer have provided valuable information

regarding the location of archaeological features that can be targeted for further spectro-radiometry

transects next year.

Further work

y Continuing the spectro-radiometry surveys until the harvest this year (mid-August)y Locating further transects for the growing season in 2012. This will involve working closely

with the land-owners to locate transects in areas of different crop and cultivation regimes

y Designing a data structure for interrogating the datay Correction and exploration of the aerial datay Writing the NERC Airborne Remote Sensing Facility grant for the 2012 season