The coverage maps are actually Excel spreadsheets showing, respectively, the number of records and the number of different taxa recorded in each monad (kilometre square) between the year 2000 and the date they were created.
The maps were last created on 21st January 2025. Click here to download them.
The data in these maps is taken from the BSBI Distribution Database (DDb). In previous years these maps were based on the records in MapMate which are also copied to the BSBI. The change is for two reasons, firstly support for MapMate is ending in 2025 and secondly some of the vice-county recorders in Somerset are now entering records directly into the DDb using the new BSBI recording app.
The previously separate record count and taxon count maps have been included in one spreadsheet. For the first time a list of the counts for each monad is provided as well. Further notes are provided in the spreadsheet. Examples of the maps are shown below.
Record Counts

The image here shows part of the spreadsheet covering the extreme west of Somerset around Simonsbath, Exmoor.
This shows the recording effort per monad since the year 2000. Some areas have been visited on multiple occasions, such as SS7242 which contains Pinkery Pond, for which there were 600 records when this example was produced a few years ago.
Taxon Counts

This map shows the number of different vascular plant taxa recorded. This is a better guide to the botanical richness of the monad, provided there has been sufficient recording effort. It can be seen that at the time the 600 records in SS7242 relate to 151 different taxa.
Method
The original method was kindly provided by Brian Pitkin of Surrey Botanical Society. The method relies on a list of 1km squares (also known as monads e.g. ST5036) originally sourced from the Biological Records Centre. This data was also provided by Brian Pitkin as a map-like spreadsheet, showing the percentage of each square contained within VC 5 and VC 6. Note that each vice-county extends to low water mark, which accounts for the large coastal expanse of squares with no records, particularly around the mouth of the Parrett. In addition, the BSBI Grid Reference lookup was found to be very useful in checking grid references against the VC boundaries.
Data is downloaded from the BSBI DDb using a number of queries to acquire record and taxon counts for all of the Vice-counties South Somerset (VC5) and North Somerset (VC6) plus small areas of South Devon (VC3) and Dorset (VC9) which are now within the local authority area of Somerset. Microsoft Access is used to generate the counts which is then exported to an Excel spreadsheet for distribution.
Conditional Formatting has been used to colour each square according to its value. Again, this was designed by Brian Pitkin, although I have changed the colours and added some more categories, so we now have the following colours:
