Grabbing grid-references

All botanical ‘records’ need to be fixed by 1) a site-name, and 2) an Ordnance Survey grid-reference (GR), the resolution of which can be adjusted to suit. The site-name is best extracted from the O.S. 1:25 000 map, giving the nearest appropriate name to the site.

Common plants will not usually need a GR better than the monad (1km × 1km square, with a GR looking like NY4567 – a ‘four-figure’ GR). Any significant finds should have at least a ‘six-figure’ GR (like NY123567 – defining a 100m × 100m square). However, an ‘eight-figure’ GR (like SD12346789 – defining a 10m × 10m square) is very much better.

GPS readers, such as in GPS meters, and in mapping apps on GPS-enabled smart-phones and tablets, will deliver a ten-figure GR (ostensibly defining a 1m × 1m square on the ground). However, this degree of accuracy is rarely actually achieved (without more specialized equipment). Hence it is usual to reduce 10-figure GRs from such devices to 8-figure GRs for the purposes of records, by removing the last digits of the northing and easting (thus NY1234/5/0123/4/ would lose the /bolded/ digits to become NY12340123. (Incidentally, do not use ’rounding’.) An alternative might be to employ (for instance) Grab a Grid Reference Duo, as below, and copy its 8-figure read-out.

In addition to a GR, the quality cameras in so many devices these days allow ‘pinpointing’ plants by photographing a series of wider and narrower views of the site. Where necessary, these can be overlaid by arrows on the digital pictures with suitable software – just google.

Grab a Grid Reference Duo

Online mapping facilities can greatly facilitate deriving GRs. Currently the most-used site is Grab a Grid Reference Duo ‘duo’ because it has both aerial and map views). Its learning curve is remarkably short, and I have made a simple Grab a Grid Ref user guide to help.

This can be used to overlay on the map or aerial view any grid-square from hectad (10km square), tetrad (2km square), monad (1km square), right down to eight-figure GRs, and vice-county boundaries, and more. Extremely useful!

Another app worth exploring is Cucaera.

JR March 2018

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