Convert a polar scan into a raster

Converts an object of class scan into a raster of class RasterBrick.

Usage

scan_to_raster(
  scan,
  nx = 100,
  ny = 100,
  xlim,
  ylim,
  res = NA,
  param,
  raster = NA,
  lat,
  lon,
  crs = NA,
  k = 4/3,
  re = 6378,
  rp = 6357
)

Arguments

scan

a scan (sweep) of class scan

nx

number of raster pixels in the x (longitude) dimension

ny

number of raster pixels in the y (latitude) dimension

xlim

x (longitude) range

ylim

y (latitude) range

res

numeric vector of length 1 or 2 to set the resolution of the raster (see res). If this argument is used, arguments nx and ny are ignored. Unit is identical to xlim and ylim.

param

scan parameters to include. If NA include all scan parameters. Reducing the number of scan parameters speeds up evaluation.

raster

(optional) raster::RasterLayer or terra::SpatRaster with a CRS. When specified this raster topology is used for the output, and nx, ny, res arguments are ignored.

lat

Geodetic latitude of the radar in degrees. If missing taken from scan.

lon

Geodetic longitude of the radar in degrees. If missing taken from scan.

crs

character or object of class CRS. PROJ.4 type description of a Coordinate Reference System (map projection). When 'NA' (default), an azimuthal equidistant projection with origin at the radar location is used. To use a WSG84 (lat,lon) projection, use crs="+proj=longlat +datum=WGS84"

k

Numeric. Standard refraction coefficient.

re

Numeric. Earth equatorial radius, in km.

rp

Numeric. Earth polar radius, in km.

Value

a RasterBrick

Details

uses scan_to_spatial to georeference the scan's pixels. If multiple scan pixels fall within the same raster pixel, the last added pixel is given (see rasterize for details).

See also

Other raster functions: scan_to_spatial()

Examples

# \donttest{
# default projects full extent on 100x100 pixel raster:
scan_to_raster(example_scan)
#> class      : RasterBrick 
#> dimensions : 100, 100, 10000, 5  (nrow, ncol, ncell, nlayers)
#> resolution : 4791.787, 4791.787  (x, y)
#> extent     : -239589.3, 239589.3, -239589.3, 239589.3  (xmin, xmax, ymin, ymax)
#> crs        : +proj=aeqd +lat_0=56.3675003051758 +lon_0=12.8516998291016 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs 
#> source     : memory
#> names      :       DBZH,      VRADH,      RHOHV,        ZDR,      PHIDP 
#> min values :  -12.00000,  -21.43643,    0.02680,  -14.87059, -178.58824 
#> max values :  32.000000,  20.684274,   0.999300,   7.905883, 178.588244 
#> 

# crop the scan and project at a resolution of 0.1 degree:
scan_to_raster(example_scan, ylim = c(55, 57), xlim = c(12, 13), res = .1)
#> class      : RasterBrick 
#> dimensions : 20, 10, 200, 5  (nrow, ncol, ncell, nlayers)
#> resolution : 0.1, 0.1  (x, y)
#> extent     : 12, 13, 55, 57  (xmin, xmax, ymin, ymax)
#> crs        : +proj=aeqd +lat_0=56.3675003051758 +lon_0=12.8516998291016 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs 
#> source     : memory
#> names      :         DBZH,        VRADH,        RHOHV,          ZDR,        PHIDP 
#> min values :           NA,   -0.1880389,    0.9254000,   -0.7529409, -103.7647040 
#> max values :           NA,    0.3760777,    0.9951000,    0.6588239,  -27.5294080 
#> 

# using a template raster (a terra SpatRaster can be passed directly):
template_raster <- terra::rast(terra::ext(12, 13, 56, 58), crs = "epsg:4326")
scan_to_raster(example_scan, raster = template_raster)
#> class      : RasterBrick 
#> dimensions : 10, 10, 100, 5  (nrow, ncol, ncell, nlayers)
#> resolution : 0.1, 0.2  (x, y)
#> extent     : 12, 13, 56, 58  (xmin, xmax, ymin, ymax)
#> crs        : +proj=longlat +datum=WGS84 +no_defs 
#> source     : memory
#> names      :        DBZH,       VRADH,       RHOHV,         ZDR,       PHIDP 
#> min values :   -8.000000,  -20.684274,    0.078400,   -9.882353, -161.647058 
#> max values :   18.000000,   14.478992,    0.952100,    7.905883,  147.529420 
#> 
# }