extent: Create extents from geometries
In osdatahub: Easier Interaction with the Ordnance Survey Data Hub

extent

R Documentation

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) format, 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.

Using crs='epsg:4326' implies that coordinates will be in Latitude/Longitude order. The equivalent projection with Longitude/Latitude order is 'crs84'.

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')

# When using EPSG:4326, note the coordinate order expects latitude, longitude
extent_from_bbox(c(50.928731, -1.503346, 50.942376, -1.46762), crs="epsg:4326")

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

extent_from_bng("SU3715")

osdatahub documentation built on April 11, 2025, 5:52 p.m.