BKG WFS

Low-level interface to BKG-style web feature services (WFS). This function is used in all high-level functions of ffm that depend on a WFS, e.g., bkg_admin.

bkg_feature_types lists all available feature types for a given endpoint.

Usage

bkg_wfs(
  type_name,
  endpoint = type_name,
  version = "2.0.0",
  method = NULL,
  format = "application/json",
  layer = NULL,
  epsg = 3035,
  properties = NULL,
  filter = NULL,
  server = sgx_base(),
  ...
)

bkg_feature_types(endpoint, server = sgx_base())

Arguments

type_name

Feature type of the WFS to retrieve. You can use bkg_feature_types to retrieve a list of feature type names for a given endpoint.

endpoint

Endpoint to interface. Note that wfs_ is appended and only the rest of the product name must be provided. For example, wfs_vg250 becomes vg250. Defaults to the value of type_name.

version

Service version of the WFS. Usually 2.0.0, but some services still use 1.0.0 or 1.1.0.

method

HTTP method to use for the request. GET requests provide parameters using URL queries. Filters must be provided as CQL queries. While this is less error-prone, it allows a maximum number of only 2048 characters. Especially when providing more sophisticated spatial queries, GET queries are simply not accepted by the services. In these cases it makes sense to use POST requests instead.

If NULL, the method is inferred from the type of filter query provided to filter (either XML or CQL). If no filter is provided, the method is inferred from getOption("ffm_query_language").

format

Content type of the output. This value heavily depends the endpoint queried. Most services allow application/json but some only support GML outputs. When in doubt, inspect the GetCapabilities of the target service. Defaults to "application/json".

layer

If format specifies a GML output, layer specifies which layer from the downloaded GML file to read. Only necessary if the GML file actually contains multiple layers. Defaults to NULL.

epsg

Numeric value giving the EPSG identifier of the coordinate reference system (CRS). The EPSG code is automatically formatted in a OGC-compliant manner. Note that not all EPSG codes are supported. Inspect the GetCapabilities of the target service to find out which EPSG codes are available. Defaults to EPSG:3035.

properties

Names of columns to include in the output. Defaults to NULL (all columns).

filter

A WFS filter query (CQL or XML) created by wfs_filter.

server

WFS server domain to use. Defaults to the SGX spatial data center of the BKG.

...

Further parameters passed to the WFS query. In case of POST requests, additional namespaces that may be necessary to query the WFS. Argument names are interpreted as the prefix (e.g. xmlns:wfs) and argument values as namespace links.

Value

An sf tibble

Examples

bkg_feature_types("vg5000_0101")
#> # A tibble: 7 × 3
#>   name                   title                   abstract               
#>   <chr>                  <chr>                   <chr>                  
#> 1 vg5000_0101:vg5000_lan Bundesland              Bundesland             
#> 2 vg5000_0101:vg5000_gem Gemeinde                Gemeinde               
#> 3 vg5000_0101:vg5000_li  Grenzlinien             Grenzlinien            
#> 4 vg5000_0101:vg5000_krs Kreis                   Kreis                  
#> 5 vg5000_0101:vg5000_rbz Regierungsbezirk        Regierungsbezirk       
#> 6 vg5000_0101:vg5000_sta Staat                   Staat                  
#> 7 vg5000_0101:vg5000_vwg Verwaltungsgemeinschaft Verwaltungsgemeinschaft

bkg_wfs(
  "vg5000_lan",
  endpoint = "vg5000_0101",
  count = 5,
  properties = "gen",
  epsg = 4326
)[-1]
#> Simple feature collection with 5 features and 1 field
#> Geometry type: MULTIPOLYGON
#> Dimension:     XY
#> Bounding box:  xmin: 5.866 ymin: 50.3227 xmax: 11.5977 ymax: 55.0571
#> Geodetic CRS:  WGS 84
#> # A tibble: 5 × 2
#>   gen                                                                   geometry
#>   <chr>                                                       <MULTIPOLYGON [°]>
#> 1 Schleswig-Holstein  (((8.7131 54.6776, 8.7068 54.6716, 8.6869 54.6709, 8.6813…
#> 2 Hamburg             (((8.4593 53.9573, 8.4326 53.9449, 8.4203 53.9473, 8.438 …
#> 3 Niedersachsen       (((6.8655 53.5847, 6.8527 53.59, 6.8637 53.5967, 6.8753 5…
#> 4 Bremen              (((8.5625 53.5491, 8.5233 53.592, 8.5099 53.6031, 8.5185 …
#> 5 Nordrhein-Westfalen (((8.9697 51.5058, 8.8907 51.482, 8.921 51.4457, 8.9195 5…

# Filters are created using `wfs_filter()`
bkg_wfs(
  "vg5000_krs",
  endpoint = "vg5000_0101",
  properties = "gen",
  filter = wfs_filter(sn_l == 10)
)[-1]
#> Simple feature collection with 6 features and 1 field
#> Geometry type: MULTIPOLYGON
#> Dimension:     XY
#> Bounding box:  xmin: 4057338 ymin: 2892729 xmax: 4132336 ymax: 2951744
#> Projected CRS: ETRS89-extended / LAEA Europe
#> # A tibble: 6 × 2
#>   gen                                                                   geometry
#>   <chr>                                                       <MULTIPOLYGON [m]>
#> 1 Regionalverband Saarbrücken (((4090660 2904942, 4092223 2901447, 4091999 2900…
#> 2 Merzig-Wadern               (((4078929 2926191, 4077635 2927692, 4074266 2926…
#> 3 Neunkirchen                 (((4111255 2917867, 4109992 2917974, 4109230 2919…
#> 4 Saarlouis                   (((4098717 2933513, 4101455 2934901, 4101490 2932…
#> 5 Saarpfalz-Kreis             (((4122248 2915965, 4120329 2917230, 4120301 2920…
#> 6 St. Wendel                  (((4105098 2950381, 4106357 2951744, 4108456 2950…

Usage

Arguments

Value

See also

Examples