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.

Hence, common plants will not usually need a GR better than the monad (1km × 1km square, which would have a GR looking like NY4567 – i.e. a ‘four-figure’ GR). Any more significant finds should have at least ‘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 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.

A different, and – with quality cameras in so many devices these days – a practical approach to ‘pinpointing’ plants is to photograph a series of wider and narrower views of the site, and then where necessary overlay arrows on the digital pictures with suitable software.

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 display any grid-square from hectad (10km x 10km square), tetrad (2km x 2km square), monad, right down to eight-figure GRs, and vice-county boundaries, and more.

Another app worth exploring is Cucaera.

JR March 2017

⇠ Back to: Resources

Leave a Reply

Your email address will not be published. Required fields are marked *