Read a WFS layer as an sf object

Improves on the v1 importer in four ways: the protocol version is taken from the negotiated capabilities rather than hard-coded, large layers are fetched page by page instead of in one request that times out, a spatial or attribute filter can be pushed down to the server, and if the endpoint cannot produce GeoJSON the request falls back to GML.

Usage

argentum_read_wfs(
  x,
  layer,
  bbox = NULL,
  crs = NULL,
  max_features = NULL,
  page_size = arg_opt("argentum.page_size"),
  filter = NULL,
  quiet = arg_opt("argentum.quiet")
)

Arguments

x

An organization name from argentum_organizations(), or a WFS URL.

layer

Layer (feature type) name, as reported by argentum_layers().

bbox

Optional spatial filter. Either a numeric vector c(xmin, ymin, xmax, ymax), or any object accepted by sf::st_bbox(), such as an existing sf object.

crs

Coordinate reference system to request, e.g. "EPSG:4326" or 4326. NULL (default) negotiates one from the layer's declared list, preferring EPSG:4326; if the layer declares none, the server's own default is used.

max_features

Stop after this many features. NULL (default) reads everything.

page_size

Features per request. Defaults to getOption("argentum.page_size"). Set to Inf to disable paging for servers that mishandle startIndex.

filter

A CQL filter pushed to the server, e.g. "provincia = 'Mendoza'". Supported by GeoServer; ignored by some ArcGIS deployments.

quiet

Suppress progress messages.

Value

An sf data frame. Zero rows if the filter matches nothing.

Details

When a read fails outright the request is retried with paging disabled and then against each older protocol version, exactly as the ArgentinaGeoServices QGIS plugin does: several Argentine GeoServer installs advertise 2.0.0 and then fail to serialise GML in that version while answering 1.0.0 perfectly. If every attempt fails, the server is asked for a single feature so that its own error message can be reported instead of a bare parse failure.

See also

argentum_download() to write layers straight to disk.

Examples

# \donttest{
url <- "https://wms.ign.gob.ar/geoserver/ows"

# Everything in a small layer
provinces <- argentum_read_wfs(url, "ign:provincia")
#> ℹ Reading ign:provincia (page 1)
#> ✔ Reading ign:provincia (page 2) [2m 2.9s]
#> 
#> ✔ Read 24 features from ign:provincia.

# Only what falls inside a bounding box, reprojected
argentum_read_wfs(
  url, "ign:provincia",
  bbox = c(-59, -35, -57, -34),
  crs = 4326
)
#> ℹ Reading ign:provincia (page 1)
#> ✔ Reading ign:provincia (page 2) [9.5s]
#> 
#> ✔ Read 3 features from ign:provincia.
#> Simple feature collection with 3 features and 9 fields
#> Geometry type: MULTIPOLYGON
#> Dimension:     XY
#> Bounding box:  xmin: -63.38594 ymin: -41.03791 xmax: -56.66499 ymax: -30.15897
#> Geodetic CRS:  WGS 84
#>             id gid entidad                             fna             gna
#> 1 provincia.54  54       0 Ciudad Autónoma de Buenos Aires Ciudad Autónoma
#> 2 provincia.68  68       0       Provincia de Buenos Aires       Provincia
#> 3 provincia.70  70       0         Provincia de Entre Ríos       Provincia
#>                               nam in1       fdc sag
#> 1 Ciudad Autónoma de Buenos Aires  02 Geografía IGN
#> 2                    Buenos Aires  06 Geografía IGN
#> 3                      Entre Ríos  30 Geografía IGN
#>                         geometry
#> 1 MULTIPOLYGON (((-58.45535 -...
#> 2 MULTIPOLYGON (((-60.24091 -...
#> 3 MULTIPOLYGON (((-58.58534 -...
# }