List what a spatial file contains
geo_layers.Rdgeo_layers() looks inside a file before you read it and returns a tidy
table of its contents:
vector files (GeoPackage, GDB, GPX, OSM, KML, ...): one row per layer, with geometry type, number of features and fields;
netCDF, HDF and GRIB files: one row per variable or subdataset, with its description, grid size and number of layers (time steps, depths or bands); pass the
varvalue togeo_read();AutoCAD (
.dxf,.dwg) and MicroStation (.dgn) drawings: one row per CAD layer or level, with its number of entities; pass thecad_layervalue togeo_read();other rasters: one row per band.
Examples
# ERA5 monthly climate at the Nouragues station, French Guiana (netCDF)
nc <- system.file("ex/nouragues.nc", package = "terra")
geo_layers(nc)
#> # A tibble: 7 × 6
#> var description nrow ncol layers source
#> <chr> <chr> <int> <int> <int> <chr>
#> 1 u10 u10 (16-bit integer) 3 3 48 "NETC…
#> 2 v10 v10 (16-bit integer) 3 3 48 "NETC…
#> 3 d2m d2m (16-bit integer) 3 3 48 "NETC…
#> 4 t2m t2m (16-bit integer) 3 3 48 "NETC…
#> 5 sp surface_air_pressure (16-bit integer) 3 3 48 "NETC…
#> 6 tp tp (16-bit integer) 3 3 48 "NETC…
#> 7 ssrd surface_downwelling_shortwave_flux_in_air (16… 3 3 48 "NETC…
t2m <- geo_read(nc, var = "t2m")
t2m
#> class : SpatRaster
#> size : 3, 3, 48 (nrow, ncol, nlyr)
#> dimensions : longitude, latitude, expver, time (3, 3, 2, 24}
#> resolution : 0.1005001, 0.0999999 (x, y)
#> extent : -52.90525, -52.60375, 3.911, 4.211 (xmin, xmax, ymin, ymax)
#> coord. ref. : lon/lat WGS 84 (CRS84) (OGC:CRS84)
#> source : nouragues.nc
#> varname : t2m (2 metre temperature)
#> names : t2m_e~r=1_1, t2m_e~r=1_2, t2m_e~r=1_3, t2m_e~r=1_4, t2m_e~r=1_5, t2m_e~r=1_6, ...
#> unit : K
#> depth : 1 to 5 (expver: 2 steps)
#> time : 2021-01-01 00:00:00 to 2022-12-01 00:00:00 (24 steps)
# Sentinel-2 Level-2A bands over Luxembourg
geo_layers(system.file("ex/sent2_L2A_2024-08-24.tif", package = "terra"))
#> # A tibble: 4 × 5
#> band name nrow ncol crs
#> <int> <chr> <dbl> <dbl> <chr>
#> 1 1 B02 90 95 WGS 84
#> 2 2 B03 90 95 WGS 84
#> 3 3 B04 90 95 WGS 84
#> 4 4 B08 90 95 WGS 84
# Luxembourg cantons written to AutoCAD DXF, then one CAD layer read back
lux <- sf::st_read(system.file("ex/lux.shp", package = "terra"), quiet = TRUE)
lux <- sf::st_cast(lux[, "NAME_1"], "MULTILINESTRING")
names(lux)[1] <- "Layer"
dxf <- tempfile(fileext = ".dxf")
sf::st_write(lux, dxf, driver = "DXF", quiet = TRUE)
geo_layers(dxf)
#> # A tibble: 3 × 3
#> cad_layer entities geometry
#> <chr> <int> <chr>
#> 1 Diekirch 5 LINESTRING
#> 2 Grevenmacher 3 LINESTRING
#> 3 Luxembourg 4 LINESTRING
geo_read(dxf, cad_layer = "Diekirch", crs = 4326)
#> Simple feature collection with 5 features and 6 fields
#> Geometry type: LINESTRING
#> Dimension: XY
#> Bounding box: xmin: 5.74414 ymin: 49.69933 xmax: 6.315773 ymax: 50.18162
#> Geodetic CRS: WGS 84
#> Layer PaperSpace SubClasses Linetype EntityHandle Text
#> 1 Diekirch NA AcDbEntity:AcDbPolyline <NA> 20000 <NA>
#> 2 Diekirch NA AcDbEntity:AcDbPolyline <NA> 20001 <NA>
#> 3 Diekirch NA AcDbEntity:AcDbPolyline <NA> 20002 <NA>
#> 4 Diekirch NA AcDbEntity:AcDbPolyline <NA> 20003 <NA>
#> 5 Diekirch NA AcDbEntity:AcDbPolyline <NA> 20004 <NA>
#> geometry
#> 1 LINESTRING (6.026519 50.177...
#> 2 LINESTRING (6.178368 49.876...
#> 3 LINESTRING (5.881378 49.870...
#> 4 LINESTRING (6.131309 49.972...
#> 5 LINESTRING (5.977929 50.026...