Convert between Irish grid references and Irish Grid coordinates or an sf object.
An Irish grid reference consists of a letter, optionally followed by an easting and northing. Each Irish grid reference refers to a square on the Irish Grid (EPSG:29903). A letter alone (e.g. “N”) refers to a particular 100 km square. An Irish grid reference with a 1-digit easting and northing (e.g. “N85”) refers to a 10 km square. A 5-digit easting and northing (e.g. “N 12345 67890”) refers to a 1 m square.
This package supports Irish grid references of 1 m, 10 m, 100 m, 1 km, 10 km and 100 km precision. Irish grid references can be of mixed precision, and whitespace between letter, easting and northing is optional.
When converting Irish grid references to point locations (using
igr_to_ig(), or st_igr_as_sf() with the
default polygons=FALSE), the south west corners of the
relevant Irish Grid squares are returned. When converting to polygons
(using st_igr_as_sf() with polygons=TRUE), the
polygons returned span the entire square of each grid reference.
The functions st_igr_as_sf() and
st_irishgridrefs() convert to and from sf (simple feature) objects
in any coordinate reference system.
To install the production version of igr from CRAN:
install.packages("igr")To install the development version of igr from GitHub:
# Install remotes package if needed
install.packages("remotes")
# Install development version of igr package from GitHub
remotes::install_github("digitalnature-ie/igr")To check validity of Irish grid references:
igr_is_valid() indicates which elements in a character
vector are valid Irish grid referencesTo convert from Irish grid references:
igr_to_ig() converts from a vector of Irish grid
references to a matrix of Irish Grid coordinatesst_igr_as_sf() converts from a data.frame containing
Irish grid references to an sf object containing points or polygonsTo convert to Irish grid references:
ig_to_igr() converts from a list or matrix of Irish
Grid coordinates to Irish grid referencesst_irishgridrefs() converts from an sf object to Irish
grid referenceslibrary(igr)
# Sample grid references
igrs <- c("A", "A16", "A123678", "BAD", "I12", "", "B125", "Z")
igr_is_valid(igrs)
#> [1] TRUE TRUE TRUE FALSE FALSE FALSE FALSE TRUE# Sample grid references
igrs <- c("A", "D12", "J53", "M5090", "N876274", "S1234550000", "W")
# Converting to Irish Grid coordinates
igr_to_ig(igrs)
#> $x
#> [1] 0 310000 350000 150000 287600 212345 100000
#>
#> $y
#> [1] 400000 420000 330000 290000 227400 150000 0
# Sample grid references in a data.frame
igrs_df <- data.frame(igr = igrs)
# Converting to an sf object of POINT features
st_igr_as_sf(igrs_df, "igr")
#> Simple feature collection with 7 features and 1 field
#> Geometry type: POINT
#> Dimension: XY
#> Bounding box: xmin: 0 ymin: 0 xmax: 350000 ymax: 420000
#> Projected CRS: TM75 / Irish Grid
#> igr geometry
#> 1 A POINT (0 4e+05)
#> 2 D12 POINT (310000 420000)
#> 3 J53 POINT (350000 330000)
#> 4 M5090 POINT (150000 290000)
#> 5 N876274 POINT (287600 227400)
#> 6 S1234550000 POINT (212345 150000)
#> 7 W POINT (1e+05 0)
# Converting to an sf object of POLYGON features
st_igr_as_sf(igrs_df, "igr", polygon = TRUE)
#> Simple feature collection with 7 features and 1 field
#> Geometry type: POLYGON
#> Dimension: XY
#> Bounding box: xmin: 0 ymin: 0 xmax: 360000 ymax: 5e+05
#> Projected CRS: TM75 / Irish Grid
#> igr geometry
#> 1 A POLYGON ((1e+05 5e+05, 1e+0...
#> 2 D12 POLYGON ((320000 430000, 32...
#> 3 J53 POLYGON ((360000 340000, 36...
#> 4 M5090 POLYGON ((151000 291000, 15...
#> 5 N876274 POLYGON ((287700 227500, 28...
#> 6 S1234550000 POLYGON ((212346 150001, 21...
#> 7 W POLYGON ((2e+05 1e+05, 2e+0...
# Sample Irish Grid coordinates
p <- matrix(c(0, 490000, 400000, 0, 453000, 4000), ncol = 2, byrow = TRUE)
colnames(p) <- c("x", "y")
p
#> x y
#> [1,] 0 490000
#> [2,] 400000 0
#> [3,] 453000 4000
# Convert to Irish grid references
ig_to_igr(p)
#> [1] "A000900" "Z000000" "Z530040"
# Sample Irish Grid coordinates in an sf object
p_sf <- sf::st_as_sf(data.frame(p), crs = 29903, coords = c("x", "y"))
# Convert sf object to Irish grid references
st_irishgridrefs(p_sf, sep = " ")
#> [1] "A 000 900" "Z 000 000" "Z 530 040"# Append Irish grid references to original sf object (using base R)
p_sf$igr <- st_irishgridrefs(p_sf)
# Append Irish grid references to original sf object (using tidy R)
p_sf <- p_sf |>
dplyr::mutate(igr = st_irishgridrefs(p_sf))This package is designed to work seamlessly in tidy R. Function names, parameter names, and function behaviour attempt to follow conventions in related R packages such as sf.
igr is written using base R where possible to minimise package dependencies, and adopts the tidyverse coding style.
R Packages, 2nd edition, by Hadley Wickham and Jennifer Bryan was of great assistance during package development.
Please log any unexpected behaviour or suggestions via GitHub Issues.