Magnetometer Results

20170312MagSurveyThe map on the left shows the magnetometer results obtained on 12 March 2017 as processed by Mike Gill using Snuffler software, georeferenced and plotted on our Millhams mapping. The light blue background shows the nominal area of the area surveyed which is a 20m-wide strip running approximately north-south for about 50m. The survey results in grey-scale are superimposed on the blue background which shows through in areas where no results could be obtained because they were inaccessible or overgrown. In the middle of the patch, there were several beehives which are intrepid surveyor approached with caution since their inhabitants were quite active in spite of the chilly weather and became more so as the day warmed up.

The results showed little in the way of structure which we could interpret either as archaeological or geological features. One striking magnetic anomaly is shown at the north-east of the survey grid which we believe may indicate a large buried ferrous object which may repay some excavation to determine its nature.

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Magnetometer at Millhams

OLYMPUS DIGITAL CAMERAAs our first activity of 2017, member Mike Gill carried out magnetometer survey on 12 March of the north garden area at Little Millhams. This area becomes heavily overgrown later in the year, and we have found the bees from the hives located there to become quite aggressive when we approach too close, so carrying out the survey early in the year seemed a good plan.

We borrowed a magnetic gradiometer made available by Bournemouth University as part of the LoCate project, and held by the New Forest National Park Authority at Lymington. A number of our members have been trained in the use of the gradiometer and Mike Gill, pictured here in action at Millhams, has obtained impressive results from the equipment on other sites.

OLYMPUS DIGITAL CAMERAWith much anticipation we were able to view the results on site without delay.  Although there were no obvious rectilinear features suggestive of structures, some aspects of the data will repay further study and perhaps some tweaking of the grey-scale display.  We were able to complete the best part of 3 x 20m grid squares in the garden, constrained by the topography of the site, the watercourses and various fallen trees which, all in all , constituted a very successful day.

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David Eels’s New Book Published

debookMembers will be aware of David Eels’s first book which TCA published “The Medieval Markets and Fairs of Christchurch”. We were uncertain as to how popular this would be but we were very pleased that the book achieved sales of several hundreds and made a welcome contribution to TCA funds. (The booklet is still in print and we are able to offer copies to TCA members at a discount off the cover price of £3.50). David is to be congratulated on the appearance of his second book, “Lords of Christchurch 1331-1480s”, in this case, published in an attractive format by Natula Publications of Christchurch.

The book presents David’s work on the unravelling of the complex ownership of the estates of Christchurch, Ringwood and the Manor of Westover, which encompasses much of modern-day Bournemouth, and tells the story of the Montacute earls of Salisbury and their lineal descendants through marriage who bore the surnames of Neville and Plantagenet. David relates the history in an entertaining way, showing how much of local history can be linked to prominent people and important events in our national history.

Copies of the book can be purchased from Amazon or from Natula Publications at their stall in the Christchurch Emporium or from their website. David has offered to make available copies of the book at a discount on the cover price to TCA members who apply directly to him. TCA is grateful that David has assigned the royalties arising from book sales to TCA funds and part of the profits from direct sales, with the remainder going to the fund for the purchase of the Boldre hoard by St. Barbe Museum.

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Millhams LIDAR Data

millhams_plot
We have been dabbling with a remarkable source of free topographical data provided by the Environment Agency which makes available the data arising from LIDAR surveys. Light Detection and Ranging (LIDAR) is an airborne mapping technique, which uses a laser to measure the distance between the aircraft and the ground, which when combined with information from the aircraft’s navigational system,provides a remarkable view of the ground surface, sometimes revealing features not readily apparent. For Christchurch, such data is available at a resolution of 50cm and we have been using the processed Digital Terrain Model (DTM) which is produced from the basic Digital Surface Model (DSM) obtained during survey by filtering out by software the heights of vehicles, buildings and vegetation.

For what it’s worth, the illustration above shows the result of processing the LIDAR data within a Geographical Information System (GIS), using colour to show ground elevation and hill-shade to enhance any features. The colour scheme has set so as to enhance the number of levels associated with the lower, riverside and meadow areas around Millhams. We found this article very useful in processing the data.  The map has been annotated such that members can find their way around it – Millhams Street and Ducking Stool Lane are apparent on the map.  Unfortunately there is little new which can be gleaned from the map , but with patience the presence of the watercourses and channels running across near the site can be discerned.

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Recording the Beam Profile

OLYMPUS DIGITAL CAMERAWe have continued to work on Pit 20 and the beam which it contains, this appearing to be the central part of the mechanism which at one time stood on the site. The large beam has a complicated profile on its upper surface and we have a problem as to how best to record the intricacies of its form, which defy our artistic talent. Mike Tizzard has hit upon the idea of using expanding polyurethane builder’s foam which when set is impervious to the water which floods the pit continually: the photo to the left shows the result from one section of the beam.

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Millhams Mapping

millhamspotteryThe Millhams project has been mapped using software Map Maker Gratis, a free version of the mapping software, Map Maker.  Map Maker Gratis has a number of excellent features but we now find that we require extended mapping techniques, particularly to incorporate overlays to show the results of the finds distribution analysis currently being undertaken.  We have therefore decided to migrate the mapping to the open-source software QGIS.  This has necessitated some rework in exporting vector data from the proprietary format used by Map Maker to the more cumbersome shapefiles used in QGIS.  The image files (raster data) also require to the georeferenced again in QGIS.  This process is nearly complete and an interim example of the output from QGIS, showing an overlay depicting the density of medieval pottery finds (analysis not yet complete) is shown above.

The QGIS project file will be placed in Dropbox and the Map Maker project file will no longer be maintained.  Interested members will need to install QGIS on their computer in order to view the project and to take full advantage of the mapping.  QGIS is being updated constantly; the version on which the above map was produced is QGIS 2.8.1 (Wien).  Once installed, the software should be used to locate the millhams.prj file from Dropbox which will open the current view of the project.

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Medieval Ring Brooch from Pit 20

ring_broochIn our continuing excavation of the water-borne gravels surrounding the timber beam in the extended Pit 20, we have found this medieval ring- brooch pictured to the left. The gravel layer is where most of our finds occur although metal objects, apart from nails are rare.

The brooch shows signs of silver-plating of which a few flecks remain and there is an indistinct design incised into the metal ring. The brooch was discovered during routine sieving operations on the gravel by member Laureen Pearce who also took the photograph.

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