extent {osdatahub}

Create extents from geometries

Description

Provide extents from various types of input features and geometries to be used as filters in OS Data Hub API queries.

Usage

extent_from_bbox(bbox, crs = "crs84", returnType = c("qExtent", "geos", "wkt"))

extent_from_polygon(
  polygon,
  crs = "crs84",
  returnType = c("qExtent", "geos", "wkt")
)

extent_from_geojson(
  geojson,
  crs = "crs84",
  returnType = c("qExtent", "geos", "wkt")
)

extent_from_radius(
  centre,
  radius,
  crs = "epsg:27700",
  returnType = c("qExtent", "geos", "wkt")
)

extent_from_bng(grid_ref, returnType = c("qExtent", "geos", "wkt"))

Arguments

bbox

A bounding box, passed as a numeric vector in (xmin, ymin, xmax, ymax) or a data.frame object with numeric columns.

crs

(character or numeric) The identifier for coordinate reference system information for the feature, either in the format "epsg:xxxx" or an EPSG number. e.g. British National Grid can be supplied as "epsg:27700" or 27700. Available CRS values are: EPSG:27700, EPSG:4326, EPSG:7405, EPSG:3857, and CRS84. Defaults to CRS84.

returnType

(character) Define the object returned. The default is 'qExtent' to define a "query extent" object expected internally by osdatahub. Other options are 'wkt' to return the geometry in Well-Known Text format or 'geos' to return an object of class geos.

polygon

A polygon specified in a WKT string, an object of class geos, or an object of class sf.

geojson

A character string defining a polygon in GeoJSON format.

centre

Either a numeric vector with coordinates in the form (x, y), a Point object in a WKT string, a Point as a geos geometry or an object of class sf.

radius

(numeric) The radius of the circle in meters.

grid_ref

A character string with a British National Grid reference. The extent is formed by the grid square of the reference.

Details

When defining an extent by a radius around a point, the CRS must be either 'epsg:27700' or 'epsg:3857' which implies the units of the distance for the radius are meters.

The qExtent return option identifies a simple class of objects containing a polygon of the extent in WKT format, the bounding box coordinates, and a CRS string. It is intended to be used internally by functions in osdatahub.

Value

The coordinates of the polygon boundary as defined by returnType.

Examples

extent_from_bbox(c(600000, 310200, 600900, 310900), "epsg:27700", returnType = 'wkt')

extent_from_radius(c(441317, 112165), radius = 200)

extent_from_bng("SU3715")