Eastings_Northings: Converting Ordnance Survey grid references

In SEEG-Oxford/seegSDM: Streamlined Functions for Species Distribution Modelling in the SEEG Research Group

Description

Convert between alphanumeric Ordnance Survey grid references and all-numeric eastings/northings for the Ordnance Survey of Great Britain coordinate system (os2en & en2os)and convert Eastings/Northings into polygons (en2poly).

Usage

en2os(en)
os2en(os)
en2poly(coords)

Arguments

en	A two-column matrix of Ordnance Survey eastings (column 1) and northings (column 2) coordinates of arbitrary precision.
os	A character vector of alphanumeric Ordnance Survey grid references of arbitrary precision, optionally with DINTY tetrad letters (see references).
coords	A matrix with four columns giving (in this order) eastings of the lower-left corners of the grid squares, northings of the lower-left corners of the grid squares, eastings of the upper-right corners of the grid square, northings of the upper-right corners of the grid squares.

Value

en2os: a character vector of alphanumeric OS grid references.

os2en: a dataframe giving the lower-left and upper right corners and centre of the OS grid square in eastings/northings and the resolution (square side length) in metres.

en2poly: a SpatialPolygons object with a polygon for each grid square.

References

Ordnance Survey http://en.wikipedia.org/wiki/Ordnance_Survey 'DINTY' tetrads http://en.wikipedia.org/wiki/Tetrad_(area)

See Also

osgb36

Examples

# generate some OS grid references of differing precisions
# (note the third has a DINTY tetrad reference)
os <- c('SP320254', 'SP3209225422', 'SP320254H')
# convert them to eastings & Northings
en <- os2en(os)
en
# and back to grid references
os2 <- en2os(en[, 1:2])
# note that the eastings-northings sytem cannot handle dinty tetrads, so the information is lost
os2
# plot the polygons for the original OS coordinates
polys <- en2poly(en[, 1:4])
plot(polys, axes = TRUE)

SEEG-Oxford/seegSDM documentation built on May 9, 2019, 11:08 a.m.