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Watsonian Vice Counties

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PostPosted: Sun Nov 11, 2007 11:24 am    Post subject: Watsonian Vice Counties Reply with quote

The vice county system for Great Britain was devised in 1952 by an English botanist, H.C. Watson, for the purposes of illustrating plant distributions.

Political boundaries have altered many times since Watsonís day. Change has been both piecemeal (local minor boundary adjustments) and wholesale (as in 1974 and more recent unitary revisions). In the early years of vice county use, some naturalists tried to change vice county boundaries to match these revisions but it was soon realised that much of the value of the vice counties was in their stability. Stable boundaries make it easier to compare trends over time and also to develop and maintain national networks of vice county recorders who coordinate and validate recording in their set areas.

The real value of the Watsonian vice counties is that they are stable and recognisable units of approximately equal size. Although based on old administrative boundaries, they are, to a large extent, geographically based and therefore much more meaningful to recorders than any division made on grid squares alone could be.


The vice county system for Great Britain was devised by an English botanist, Hewett Cottrell Watson, for the purposes of illustrating plant distributions. The system first appeared in the third volume of his work Cybele Britannica in 1852 and was refined in later volumes.

The boundaries that Watson selected were principally county boundaries as drawn in an atlas published by the Society for the Diffusion of Useful Knowledge in 1844 and reflecting the political boundaries as they existed then. Watson tried to define areas of approximately equivalent size and so some of the larger counties were divided arbitrarily into two or more "vice counties". With time all of his areas came to be referred to as vice counties whether they were subdivisions of a county or not.

Watsonís map, originally published in 1852, has little detail being at a scale of 1:4,000,000 and even an updated version which appeared in Topographical Botany in 1883 is only at 1:3,000,000. He did however give written descriptions of boundaries, mainly for the sub-division of the larger counties into vice counties.

In the mid 20th Century vice counties were being used extensively to describe distributions, but naturalists now had access to detailed Ordnance Survey maps and the poor resolution of Watson's system was problematic. Consequently, the boundaries were defined in greater detail by A.J. Wilmott and J.E. Dandy under the auspices of the Systematics Association. Their work utilised a set of half-inch parish diagram maps provided by the Ordnance Survey, which showed changes of boundaries since Watsonís time and these were reviewed by the Associationís Maps and Censuses sub-committee. The outcome of this work was a set of 1:63,360 (1 inch to 1 mile) maps marked up by Dandy and lodged with the British Museum Natural History (now the Natural History Museum).

These maps were the principal source for a two-map set at 1:625,000 scale (c. 10 miles to the inch) published by the Ray Society in 1969. This set remains the key work for naturalists checking vice county boundaries and is the usual source for the system quoted in the References of publications.

With the increase use of IT systems for the storage and analysis of biodiversity data, the provision of an accurate set of vice county boundaries for use with Geographical Information Systems and recording software has become necessary. A project to digitise vice county boundaries was undertaken by the NBN in 2003 with some of the funding coming from DEFRA.

Because digitised boundaries were intended to be used in mapping and GIS systems, they needed to be at a high enough resolution to avoid jagged lines and to maintain a degree of accuracy on large scale maps. A resolution of 1:10,000 was deemed necessary since this is the scale normally used by conservation bodies and Local Authorities in relation to planning control systems. The hand drawn source maps were at 1:63,360 as explained above. It is not possible to make data more accurate than its original resolution and so the placing of lines necessarily involves interpretation. The digitisation project was therefore, more than a simple data capture exercise. It was in fact a new definition of vice county boundaries at a higher level of resolution and taking into account the changes that have occurred since Watson and Dandy's time.

The way that this was done was as follows:
  • The Dandy 1:63,360 maps from the Natural History Museum were scanned and overlaid by the Ordnance Survey Boundary Line 1:10,000 dataset. This shows current administrative boundaries, including Parishes. If the mid-point of the line shown on the Dandy map was within 50m of a line in the Boundary Line set, then the Boundary Line data was used. The great majority of the vice county boundaries plotted by Dandy did in fact coincide pretty well with current Parish boundaries.
  • If the vice county boundary line differed by more than 50m, the line was defined from other sources in the following order:
    • If the boundary was visible on contemporary 1:10,000 maps, then this was used to define the vice county boundary,
    • If the boundary was visible on historic 1:10,560 maps, then this was used to define the vice county boundary,
    • If no boundary could be found, then trace the boundary directly from the 1:63,360 scale Dandy map following the centre-line as shown on those maps.
    Watson's written descriptions of boundaries were used to aid interpretation in these cases.

The coastal boundary

Watson's and Dandy's maps do not have a coastal boundary, the vice county just heads out to sea when it encounters the coast. One of the purposes of digitising vice counties was to produce a set of closed polygons that could be used (in GIS software for example) to select observations that fall within a given vice county. To achieve this, coastal vice counties need to be closed by adding a coastal boundary to them.

But what boundary should be used? If the mean low water mark (the line that is usually used for the coast on a map) then a record of a porpoise observed from a headland will not be found to be in any vice-county by a GIS analysis. On the other hand, if a marine boundary such as the 12 mile limit to British Waters was used, then a map showing vice county boundaries will not look right! The outline won't look anything like the familiar shape of GB.

The solution adopted was to include three different coastal boundaries in the digitised set:
  • Mean low water mark from the contemporary 1:10,000 Boundary Line dataset,
  • 3 nautical mile limit,
  • 12 nautical mile limit.

The coastal boundary most suitable for a particular purpose can be chosen.

Obtaining the digitised boundaries

Zip files for individual vice-county or the whole of GB in ESRI shape file or MapInfo .MIF format can be downloaded from the NBN web site.

A free CD is also available which includes both the original data and a software tool to create user defined boundary sets. To order the CD, contact the NBN Trust directly on Tel: (01636) 670090.
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