get_wms_raster: Download WMS raster layer
In happign: R Interface to 'IGN' Web Services

get_wms_raster

R Documentation

Download WMS raster layer

Description

Download a raster layer from the IGN Web Mapping Services (WMS). Specify a location using a shape and provide the layer name.

Usage

get_wms_raster(x,
               layer = "ORTHOIMAGERY.ORTHOPHOTOS",
               res = 10,
               crs = 2154,
               rgb = TRUE,
               filename = tempfile(fileext = ".tif"),
               verbose = TRUE,
               overwrite = FALSE,
               interactive = FALSE)

Arguments

`x`	Object of class `sf` or `sfc`, located in France.
`layer`	`character`; layer name obtained from `get_layers_metadata("wms-r")` or the IGN website.
`res`	`numeric`; resolution specified in the units of the coordinate system (e.g., meters for EPSG:2154, degrees for EPSG:4326). See details for more information.
`crs`	`numeric`, `character`, or object of class `sf` or `sfc`; defaults to EPSG:2154. See `sf::st_crs()` for more details.
`rgb`	`boolean`; if set to `TRUE`, downloads an RGB image. If set to `FALSE`, downloads a single band with floating point values. See details for more information.
`filename`	`character` or `NULL`; specifies the filename or an open connection for writing (e.g., "test.tif" or "~/test.tif"). If `NULL`, uses `layer` as the filename. The default format is ".tif", but all GDAL drivers are supported.
`verbose`	`boolean`; if TRUE, message are added.
`overwrite`	`boolean`; if TRUE, the existing raster will be overwritten.
`interactive`	`logical`; if TRUE, an interactive menu prompts for `apikey` and `layer`.

Details

res: Note that setting res higher than the default resolution of the layer will increase the number of pixels but not the precision of the image. For instance, downloading the BD Alti layer from IGN is optimal at a resolution of 25m.
rgb: Rasters are commonly used to download images such as orthophotos. In specific cases like DEMs, however, a value per pixel is essential.
overwrite: The function get_wms_raster first checks if filename already exists. If it does, the file is imported into R without downloading again, unless overwrite is set to TRUE.

Value

SpatRaster object from terra package.

Examples

## Not run: 
library(sf)
library(tmap)

# Shape from the best town in France
penmarch <- read_sf(system.file("extdata/penmarch.shp", package = "happign"))

# For quick testing use interactive = TRUE
raster <- get_wms_raster(x = penmarch, res = 25, interactive = TRUE)

# For specific data, choose apikey with get_apikey() and layer with get_layers_metadata()
apikey <- get_apikeys()[4]  # altimetrie
metadata_table <- get_layers_metadata("wms-r", apikey) # all layers for altimetrie wms
layer <- metadata_table[2,1] # ELEVATION.ELEVATIONGRIDCOVERAGE

# Downloading digital elevation model values not image
mnt_2154 <- get_wms_raster(penmarch, layer, res = 1, crs = 2154, rgb = FALSE)

# If crs is set to 4326, res is in degrees
mnt_4326 <- get_wms_raster(penmarch, layer, res = 0.0001, crs = 4326, rgb = FALSE)

# Plotting result
tm_shape(mnt_4326)+
   tm_raster()+
tm_shape(penmarch)+
   tm_borders(col = "blue", lwd  = 3)

## End(Not run)

happign documentation built on Sept. 11, 2024, 7:17 p.m.