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Difficulties were caused mainly by the steepness of terrain in some areas 
creating topographic shading on the photographs, and by the large amounts 
of bare rock interspersed with some vegetation types. (See Figure 4). 
The most widespread types were Calluna-Molinia and Calluna-Molinia/ 
Tricophorum Eriophorum. Because of the sensitivity of the vegetation to 
changes in ground moisture, the degree of wetness of the site often 
corresponding to a break of slope was useful in drawing the boundary 
between some types. 
The greatest difficulties were encountered in identifying Bracken, Deschampsia 
Grassland and the mountain top communities of Rhacomitrium-Empetrum with 
varying amounts of Nardus and Bare Ground. Bracken could not, on the 
whole, be separated from other types of tall shrub understorey. Deschampsia 
grassland was easily overlooked, or its extent underestimated, as a result 
of its steeply sloping location, but identification of this type can be 
aided with the help of a geological map. Rhacomitrium-Empetrum was difficult 
to distinguish from Rhacomitrium-Empetrum with Nardus, and Bare Ground, 
due to the large amount of bare ground exposed on mountain tops, 
interspersed with a scanty vegetation cover, and the nearly white image of 
all three types. 
Data Collection and Storage 
  
In order for different types of analysis to be carried out on the data, 
and to enable comparisons over the area as a whole, it was necessary to 
feed the data, comprising 32 parameters, into a computer. This was done 
at the 1/4 km? grid level using grid square locations, to allow print outs 
in map form. Areas of habitats per grid square were measured by planimeter 
and the inter- and intra-habitat variables were measured in lengths or 
areas per square according to type of unit. Actual numbers of water bodies 
and habitats in each square were counted, and relative relief was estimated 
in metres. 
The lowland study area - Merseyside 
  
This represents a sizeable portion of the Merseyside Metropolitan planning 
region (Figure 5), comprising most of Sefton District and coast, and small 
parts of Knowsley and St. Helens Districts. The coastline is dominated 
by the Ribble Estuary in the north, with large areas of salt marsh and 
mudflats wich gradually give way to the three-to-four mile beaches and sand 
dunes of Ainsdale and Formby Point. In the south, the sand dune system 
ceases abruptly with spreading urban development at Blundellsands, a 
suburb of Liverpool. Eastward of the dune system, the land is flat and 
low lying, with isolated patches of improved mossland among permanent pasture 
and rich arable land. The area as a whole is semi-rural in character and 
much of the coastline is considered to be of outstanding value to wildlife. 
Good quality, black and white air photo prints at the scale of 1:10,000, 
and flown in May, June and September, 1974, were available for the study. 
Mapping categories were chosen according to the ability to identify the 
major land use types on the air photos.