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Below is the rasterLayer RASTER_slope in a plot (4 NAs are shown in white):

enter image description here

Here is the metadata of RASTER_slope

class      : RasterLayer 
dimensions : 4, 4, 16  (nrow, ncol, ncell)
resolution : 500, 500  (x, y)
extent     : 2227000, 2229000, 1316500, 1318500  (xmin, xmax, ymin, ymax)
crs        : +proj=lcc +lat_0=12 +lon_0=-102 +lat_1=17.5 +lat_2=29.5 +x_0=2500000 +y_0=0 +datum=WGS84 +units=m +no_defs 
source     : memory
names      : values 
values     : -143.2145, 214.1981  (min, max)

Then I used mapview to get a dynamic visualization of RASTER_slope:

> mapview(RASTER_slope)
Warning messages:
1: In showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj = prefer_proj) :
Discarded ellps WGS 84 in Proj4 definition: +proj=merc +a=6378137 +b=6378137 +lat_ts=0 +lon_0=0 +x_0=0 +y_0=0 +k=1 +units=m +nadgrids=@null +wktext +no_defs +type=crs
2: In showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj = prefer_proj) :
Discarded datum World Geodetic System 1984 in Proj4 definition
3: In showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj = prefer_proj) :
Discarded ellps WGS 84 in Proj4 definition: +proj=merc +a=6378137 +b=6378137 +lat_ts=0 +lon_0=0 +x_0=0 +y_0=0 +k=1 +units=m +nadgrids=@null +wktext +no_defs +type=crs
4: In showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj = prefer_proj) :
Discarded datum World Geodetic System 1984 in Proj4 definition

The resulting mapview object looks like this:

enter image description here

The mapview object is displaying only 2 pixels with NA.

Probably I am wrong but I have the feeling that the key here is to pass a crs to RASTER_slope in a WKT format but I do not know how to do that.

Any help will be appreciated.

Inder
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  • If you want to have an OpenStreetMap layer, this will always be in a spherical mercator projection. So, your raster layer will be reprojected to this. At the moment, this is being done automatically, with interpolation (hence different values). If you want the values to remain at their original values without interpolation, perhaps you need to reproject yourself using nearest neighbor method, before plotting. – dww May 12 '22 at 15:39

1 Answers1

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Following @dww, the key is in adding method="ngb" when calling mapview, no need to re project the rasterLayer, though. Here the code and output

mapview(RASTER_slope, method="ngb", na.color="transparent")

enter image description here

Inder
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