R: Sets or retrieves projection attributes on classes extending...

is.projected {sp} | R Documentation

## Sets or retrieves projection attributes on classes extending SpatialData

### Description

Sets or retrieves projection attributes on classes extending SpatialData; set or retrieve option value for error or warning on exceedance of geographical coordinate range, set or retrieve option value for exceedance tolerance of geographical coordinate range. Note that only “+proj=longlat +ellps=WGS84” is accepted for geographical coordinates, which must be ordered (eastings, northings); the “+ellps=” definition must be given (or expanded internally from a given “+datum=” value) for recent versions of the PROJ library, and should be set to an appropriate value.

From release 6 of the PROJ library, when used in building rgdal with GDAL >= 3, the `+datum=` key in the Proj.4 string CRS representation is deprecated, and the `+towgs84=` and `+nadgrids=` keys may be deprecated soon. For this reason, sp, rgdal and sf are starting to use WKT2 (2019) string representations. In sp, the `"CRS"` object in itself remains unchanged, but the content of its `"projargs"` slot may be degraded. To work around the degradation, a `comment` is added around the `"CRS"` object containing a WKT2 (2019) string when rgdal is available and built with PROJ >= 6 and GDAL >=3. The `wkt()` accessor function returns the WKT2 (2019) string comment belonging to the `"CRS"` object.

### Usage

    is.projected(obj)
    proj4string(obj)
    proj4string(obj) <- value
    wkt(obj)
    get_ll_warn()
    get_ll_TOL()
    get_ReplCRS_warn()
    set_ll_warn(value)
    set_ll_TOL(value)
    set_ReplCRS_warn(value)

### Arguments

`obj` | An object of class or extending Spatial-class
`value` | For `proj4string` CRS object, containing a valid proj4 string; attempts to assign an object containing “longlat” to data extending beyond longitude [-180, 360] or lattitude [-90, 90] will be stopped. For `set_ll_warn` a single logical value, if FALSE (default) error on range exceedance, if TRUE, warning. For `set_ll_TOL` the value of the power of `.Machine$double.eps` (default 0.25) to use as tolerance in testing range exceedance. `set_ReplCRS_warn` may be used to turn off warnings issued when changing object CRS with the `proj4string` replacement method (by setting `value=FALSE`).

### Details

proj4 strings are operative through CRAN package rgdal. For strings defined as “longlat”, the minimum longitude should be -180, the maximum longitude 360, the minimum latitude -90, and the maximum latitude 90. Note that the `proj4string` replacement method does not project spatial data - for this use `spTransform` methods in the rgdal package.

### Value

`is.projected` returns a logical that may be `NA`; `proj4string` returns a character vector of length 1.

### Author(s)

Edzer Pebesma, edzer.pebesma@uni-muenster.de

### See Also

CRS

### Examples

    o <- new("Spatial")
    proj4string(o) <- CRS("+init=epsg:27700")
    if (!is.null(comment(slot(o, "proj4string")))) {
      cat(strsplit(wkt(o), "\n")[[1]], sep="\n")
      cat(strsplit(wkt(slot(o, "proj4string")), "\n")[[1]], sep="\n")
    }
    is.projected(CRS("+proj=longlat"))
    is.projected(CRS("+proj=geocent"))
    is.projected(CRS("+proj=geocent +units=km"))

[Package sp version 1.4-5 Index]