Geography Reference
In-Depth Information
it trivially easy to georeference. We georeferenced the LUSGB map scans
by overlaying them on the relevant New Popular scans.
The large remaining problem is the systematic extraction of vector
features from the georeferenced images, and this work is continuing.
One way of doing this would be to manually construct polygons by
tracing around each color zone on each map, but this would be very
time-consuming and expensive, costing upward of £200,000. The alter-
native approach is to use image-processing software, in our case Erdas
Imagine, to automatically identify areas of similar colors. However, a
number of problems with the maps complicate this: their complicated
publishing history means that the original inks used to indicate a par-
ticular land use vary between map sheets, which means each sheet must
be manually calibrated separately; the place-names and other informa-
tion from the black base layer confuse the software; and a large problem
especially in upland areas is that the reddish brown used for contour
lines is indistinguishable from the red used for “agriculturally unpro-
ductive.” Although solutions have been found for these problems, all
require additional manual input, and, to date, three separate technical
studies have been funded by the Environment Agency to try to find the
best way forward.
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However, our archival research has identified another way forward,
although it does not meet the specific needs of the Environment Agency.
We located the original color separations used to prepare printing plates
for the southern national summary sheet, as shown in figure 4.4, and
covering most of England and Wales and about twenty of the one-inch
sheets published by the Stamp survey. As each separation defines just
one of the color layers, they are far more easily and accurately vectorized.
Our current research, following our own agenda with funding from the
Frederick Soddy Trust, is constructing vector versions of this national
summary sheet plus the detailed surveys of Birmingham and Dartmoor,
enabling detailed studies of change on the urban and moorland fringes.
“Modern” land use is recorded via the Land Cover 2000 digital mapping
created from satellite data by the Centre for Environment and Hydrol-
ogy. One challenge is distinguishing differences due to historical change
from differences due to the very different survey methods, but we also
have access to a detailed survey of the Brighton area made in 1996-97
