The revised map showing three parallel features in Chawton Park Wood and over the fields to the west in Ref 1 was shown to be inaccurate from the excavations in Spring 2011. Here the southern dark line of the air photo streaks from the Zig-Zag was found as a ditch at 32N. The northern running lane of the half-actus wide ditch has a centre 18S, so they are 50m or 170' apart. On the map in Ref 1 they are less than half this distance apart.
It is known that there is considerable OS map error, and the only way seen of producing an accurate map of these features was to use the OS/RAF 1947 - 9 air photo series, which the OS scaled to 6" : 1 mile, as the map.
This is shown above. We have previously confirmed the scale in this region. Chawton Park Wood is the eastern half of the photo. It is much more accurate if the air photo streaks can be made out on this air photo, rather than being transferred from another photo. Not all of the streaks from the Zig Zag were formally seen on the 1947 - 9 photo, but careful viewing did pick most of them up, and extended them considerably to the SW.
Laying a transparency of the OS 6" : 1 Mile map over this air photo, and lining up the railway and A31 (to the south of the above photo map) assuming these were surveyed more accurately, shows that features around the Zig Zag are in reasonable agreement. But the northern boundary of Chawton Park Wood (to the north of the above photo map) begins to go north of the air photo boundary as you go west. The features on the western boundary of Chawton Park Wood are considerably further north on the OS map. The field boundary to the north of the three features coming out of the wood, where we make many measurements from, is over 100' further north on the OS map. The southern boundary of this field is slightly further north on the OS map - the boundary south of that is in the right place. Features in Roe Downs Road, and the field boundaries to the west of the above air photo map are all to the north on the OS map.
Half Actus wide ditch
The centre feature is the 60 Roman feet wide ditch, with lightly metalled running lanes at the edges. The air photo clearly shows a light line in the centre - presumably a central running lane, but not found at the excavation site. In the wood it seemed that his feature drooped to the north at its eastern end. This is to be expected as the land falls steeply to the north here, and earth movement can be expected. Thus the complex feature of light and dark air photo lines is shorter than in Ref 1 - where it droops it is shown as a dashed line. We still do not understand the purpose of this feature, which appears to end at the summit of the downs, and is plain to see across this field in suitable viewing conditions as two swellings astride a depression.
Southern parallel feature
The southern feature also comes out parallel to the other two, and these air photo streaks have the signature of a Roman Road - light line bounded by dark lines 50' - 60' apart. It is most easily seen in the field west of Roe Downs Road, going to the SW corner of the above air photo map. It is more difficult to see in the field west of Chawton Park Wood, but a dark line carries on through the wood, a little to the north - and is probably a Build-up. However this line starts to droop also - the start of the droop is shown. Another dark air photo line starts at this spot with less droop - this may represent the buried Cut-Back - if it cuts into the bedrock it is likely to be more stable. On MultiMap 2000 air photo a line can be see continuing eastwards, crossing the valley, and going up the steep northern valley side. This has not been plotted on the above air photo map.
This route in the original survey was thought to be the Roman estate road - but later was thought it would not line up with finds further west (Ref 2). A connection with the Zig Zag could not be found. On the OS 1:25k map the line from the Zig Zag to the features round the Bighton Boundary and Soldrige goes between the northern and centre parallel features. We cannot be certain where the OS error is, so we will have to try and trace the two outer parallel features and see which connects with air photo streaks at Soldrige.
The remains of a terrace can be detected in Chawton Park Wood, over the region of the above dark lines, and is visible in a track at the end of them. An attempt was made to take the line of the Cut-back, and extend it to the Wood boundary, in order to confirm the terrace was part of this southern parallel feature, and to find where it cuts the Wood boundary - which will be an excavation site. The following measurements were obtained on the 3 parallel features at the Wood boundary:
From the North field boundary (NE corner of field) shortest distance to:
1a Southern Running Lane of Half-Actus Ditch on Air Photo Map = 405'. 1b On the ground = 400'.
2a Centre of Southern parallel feature on Air Photo Map = 555'
2b Where the line from the terrace in Wood cuts Wood boundary on ground = 659'
From the Southern Field Boundary (SE corner of field) along the Wood boundary to:
3a Centre of Southern parallel feature on Air Photo Map = 560'. 3b On the ground to line from terrace = 456'
The width of the field on the Air Photo Map = 2a + 3a = 555' + 560' = 1115'
The width of the field on the ground = 2b + 3b = 659' + 456' = 1115'
Thus the Air Photo Map is accurate and agrees with ground measurements for the known features of width of the field, and the position of the Southern Running Lane of Half-Actus Ditch (1a & 1b, 1b from excavation). However where the line from the terrace cuts the Wood boundary does not agree with the Air Photo Map position of the Southern parallel feature. This may result from the drooping of the air photo dark line in the Wood mentioned above due to the slope of the hillside. On the Air Photo Map the distance between the Southern Running Lane of the Half-Actus Ditch and the Northern Dark Line of Southern parallel feature = 115' - which may be a Roman Actus (which is 120 Roman feet = 116'). It is unknown what these three parallel features are doing. Surveyors: Simon & Cristina Kinghorn, Stuart Bloom. Richard Whaley.
1. Richard Whaley, Chawton Park Wood starts the Zig Zag, FAB e News Autumn 2011, www.nehhas.org.uk/rd10-11.htm
2. Richard Whaley, Into the Centuriation, NEHHAS NL 96 2005, NEHHAS Journal Vol 3, No 12, 20012.