393 - 
3d in a 
The final map provided a new data source for use by the new County- 
Planning Authorities (West, Mid and South Glamorgan) showing areas down 
to 0,25 ha, and all buildings, A further stage involved the transfer of 
(more 
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idscape, 
pit S, 
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bion in 
3 this 
of 
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i uses 
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that 
sites in excess of 1 ha, to forms for use by the Welsh Office as part 
of the Derelict Land Survey of Wales (19T^)• 
Although problems arose in all stages of the survey most were 
satisfactorily solved, but discussion must be confined to dealing only 
with sane of those aspects of the air—photo interpretation, 
Air-Photo Interpretation, 
To describe those aspects of air—photo interpretation relevant 
to all the types of derelict and spoiled land found in the survey would 
take more space than this present paper permits. Discussion will 
therefore be restricted to mining, especially coal mining which has 
contributed most to the problem of dereliction in South Wales, and 
aspects of which are illustrated on an aerial photograph in Pig, 9* 
3 he a 
t a 
Mining has been practised on various scales and in several forms 
from earliest times in South Wales, The oldest form is probably that 
found in areas where very shallow pits were dug for lead and metalliferous 
minerals (Fig, 1)* Such sites are difficult to identify from the ground 
although from the aerial photograph they are clearly recognised by their 
ling 
itribute 
hummocky surface. At the scale of photography used the texture is fine 
and tonal variations small, but the short shadows cast by the small 
mounds and shallow depressions are sufficient to accentuate the form. 
irvey 
y 
f 
s, while 
A very much more common mining feature associated with both coal and 
ironstone is that of "crop—working” or "trenching”. Originating before 
the eighteenth century the technique involved the removal of coal and/or 
ironstone bands or nodules where the seams outcropped at the land surface, 
usually on the valley slopes. The form of the resulting dereliction 
(Pig, 2) is clearly recognisable both on the ground and on the aerial 
photograph, A series of scooped out hollows or trench in the hillside 
is immediately juxtaposed with a parallel series of spoil heaps on the 
as 
downslope side. Occasionally an isolated hollow and spoil heaps are 
found where trial excavations were begun but not extended because there 
was no coal or ironstone present, or because the geological structure 
ed with 
all 
ich no 
inhibited exploitation of the seam. 
Difficulties of this nature and the gradual exhaustion of readily 
accessible minerals (cropworking rarely extended for more than several 
metres into the hillside) led to the practice of driving tunnels into the 
seam and extracting the coal and ironstone from within the ground. 
Known variously as ’levels* or ’drifts’ these mines formed a conplex 
system of tunnels whose extent depended on limiting factors such as the 
i worker. 
geology, ventilation and drainage. The appearance of these mines is 
similar to isolated cropworkings in appearing as a scopped—out hollow in 
iere 
perat ing. 
the hillside. These mark the entrances to the mine although generally 
the opening has been sealed up after abandonment. The spoil brought out 
of the mine, however, results in a different form of heap to that of