Kilometrage — bkg_kilometrage • ffm

Get kilometrages of German federal motorways. Kilometrages are markers for each kilometer of a highway. They can be used to create linear referencing systems (LRS).

Usage

bkg_kilometrage(
  ...,
  bbox = NULL,
  poly = NULL,
  predicate = "intersects",
  filter = NULL,
  epsg = 3035,
  properties = NULL,
  max = NULL
)

Arguments

...

Used to construct CQL filters. Dot arguments accept an R-like syntax that is converted to CQL queries internally. These queries basically consist of a property name on the left, an aribtrary vector on the right, and an operator that links both sides. If multiple queries are provided, they will be chained with AND. The following operators and their respective equivalents in CQL and XML are supported:

R	CQL	XML
`==`	`=`	`PropertyIsEqualTo`
`!=`	`<>`	`PropertyIsNotEqualTo`
`<`	`<`	`PropertyIsLessThan`
`>`	`>`	`PropertyIsGreaterThan`
`>=`	`>=`	`PropertyIsGreaterThanOrEqualTo`
`<=`	`<=`	`PropertyIsLessThanOrEqualTo`
`%LIKE%`	`LIKE`	`PropertyIsLike`
`%ILIKE%`	`ILIKE`
	`%in%`	`IN`

To construct more complex queries, you can use the filter argument to pass CQL queries directly. Also note that you can switch between CQL and XML queries using options(ffm_query_language = "xml"). See also wfs_filter.

bbox

An sf geometry or a boundary box vector of the format c(xmin, ymin, xmax, ymax). Used as a geometric filter to include only those geometries that relate to bbox according to the predicate specified in predicate. If an sf geometry is provided, coordinates are automatically transformed to ESPG:25832 (the default CRS), otherwise they are expected to be in EPSG:25832.

poly

An sf geometry. Used as a geometric filter to include only those geometries that relate to poly according to the predicate specified in predicate. Coordinates are automatically transformed to ESPG:25832 (the default CRS).

predicate

A spatial predicate that is used to relate the output geometries with the object specified in bbox or poly. For example, if predicate = "within", and bbox is specified, returns only those geometries that lie within bbox. Can be one of "equals", "disjoint", "intersects", "touches", "crosses", "within", "contains", "overlaps", "relate", "dwithin", or "beyond". Defaults to "intersects".

filter

A character string containing a valid CQL or XML filter. This string is appended to the query constructed through .... Use this argument to construct more complex filters. Defaults to NULL.

epsg

An EPSG code specifying a coordinate reference system of the output. If you're unsure what this means, try running sf::st_crs(...)$epsg on a spatial object that you are working with. Defaults to 3035.

properties

Vector of columns to include in the output.

max

Maximum number of results to return.

Value

A dataframe containing the following columns:

name: Geographical name of the POI
gemeinde: Municipality name
verwaltung: Administrative association name
kreis: District name
regierungs: Government region name
bundesland: Federal state name
bez: Label of the federal motorway
kilometer: Kilometrage of the motorway
richtung: Direction of the kilometrage

Query language

By default, WFS requests use CQL (Contextual Query Language) queries for simplicity. CQL queries only work together with GET requests. This means that when the URL is longer than 2048 characters, they fail. While POST requests are much more flexible and able to accommodate long queries, XML is really a pain to work with and I'm not confident in my approach to construct XML queries. You can control whether to send GET or POST requests by setting options(ffm_query_language = "XML") or options(ffm_query_language = "CQL").

Examples

if (FALSE) { # getFromNamespace("ffm_run_examples", ns = "ffm")()
# Get the kilometrage of the A2 motorway
a2 <- bkg_kilometrage(bez == "A2")
plot(a2["kilometer"], pch = 16)
}