The method used was an extension of that used in Ref 2, where a metal detector is set up as a magnetometer. When one wishes to compare particular areas of land, one can skim quickly over an area, noting the maximum and minimum readings. Obvious metal signals are ignored. As one moves over the ground the needle moves from a max to a min, and it is thought that the results may be more meaningful if they show the typical max and min readings over the area.
First of all a traverse was done in the field west of the 2011-2 excavation on the west edge of Chawton Park Wood, where the position of the two ditches was known accurately, and the start of the crushed flint metalling. One traverse was done 15 meters from the wire fence. The land was divided up into Block A, which was north of the North Ditch (D-N); a 5m Block around the North Ditch centre, which including going along the ditch but not closer than 10m from the fence; Block B between the ditches, a 5m Block around the South Ditch centre (D-S); and Block C south of the South Ditch. The results are given in Fig 1, the needle swings between the bold lines in the 5 Blocks.
The two ditches show up well. The Northern Ditch was somewhat larger than the Southern and this may result in the higher needle swings. Crushed flint started at the Southern Ditch, which may be the cause of the significantly lower minimum needle swings. The crushed flint continued north of the North Ditch (how far not yet known at the time of writing) - and exactly the same needle swings occur in Block A as in B.
Strip Fields
A traverse was done along the NE boundary of the Strip Fields at the western edge of the Air Photo Map. The position of the two ditches was estimated from the Air Photo Map, and the ditches' relation to these field corners. Results are given in Fig 2, and the ditches show up well. In this case we did not know exactly where the two ditches were. But it was clear for the southern ditch that the higher readings ended before the ditch centre was designated - and this Block redefined further south. Then it was found that a mistake had been made in defining the position of this ditch from the northern ditch by measuring 50' along the boundary - whereas the geomentry required 55' - which accounted for about half the difference.
All the Blocks A, B, C are different, and we cannot deduce anything specific about B, the expected position of the Road.
Conclusion
This method probably gives more information than taking averages, and is easier to do and report. One traverse may be sufficient to confirm the position of such features on the ground. Where there is some uncertainty this can be allowed for in constructing the Blocks.
Strip Fields: these result from feudalism and manorial organisation. Manor tenants would hold land scattered all over the manor. The main agricultural land was often in three fields, and what was grown on them was controlled by the Manor Courts - and the fields worked communally. While manor tenants with Lord of the Manor held land in the three fields it was not necessary or practical to shown this on the ground - each got a share of the crops according to his land holding. This arrangement continued late in may places - after the Civil War. But by about 1800 most tenants were working their own land - and so their holdings got turned into little Strip Fields where the three fields once were. This is common on the continent - but less in the UK - for during the 1800s other trends were occurring. By the later 1800s land holdings had changed so most farmers' lands were in one place as farms - and often on the former waste and common lands. The original three fields often got absorbed into the village or town, being built on or used for other things - in Farnborough they are two monasteries. In Medstead they may survive as this arrangement of Strip Fields - too small for modern agriculture - and seem to be used largely for ponies.
Fig 1 Traverse in field by 2011-2 excavation, 15m from the wire fence. The vertical scale is the Signal needle reading, whose swings falls within the bold lines for each Block. The North Ditch centre D-N is at 47.5N, and the Southern Ditch centre D-S at 32N. Threshold set at 10 (signals below this are reduced magnetic field). Ground Balance was 3.8, Discriminator set at 3.5 giving a signal of 20 - 30 at stubble height.
Fig 2 Traverse 15m from NE boundary of Strip Fields, the position of the ditches estimated from the Air Photo Map, details as Fig 1. Ground Balance was 3.5, Discriminator set at 1.7 giving 20 to 30 signal reading at stubble height.
REFERENCES
1. Richard Whaley, FAB e News 4, Spring 2012
http://www.nehhas.org.uk/rd11-12.htm
2. Richard Whaley, FAB e New 1, Autumn 2010
http://www.nehhas.org.uk/rd06-9.htm