Should "simple" and "bilinear" methods in extract return the same results?

[kadyb]

I thought "bilinear" method would smooth out the values compared to "simple". Is this expected?

library("terra")

f = system.file("ex/logo.tif", package = "terra")
r = rast(f)[[1]]
pts = spatSample(r, 100, method = "regular", values = FALSE, as.points = TRUE)

smp1 = extract(r, pts, method = "simple", ID = FALSE)
smp2 = extract(r, pts, method = "bilinear", ID = FALSE)

all.equal(smp1, smp2)
#> TRUE

[rhijmans]

It does, except when a point is smack in the middle of a cell, because in that case that cell gets infinite weight (1/0). And that is what you get when you sample raster cells. But if sample the extent things are different.

library("terra")
f = system.file("ex/logo.tif", package = "terra")
r = rast(f)[[1]]

pts = spatSample(as.polygons(r, ext=TRUE), 100)
smp1 = extract(r, pts, method = "simple", ID = FALSE)
smp2 = extract(r, pts, method = "bilinear", ID = FALSE)

all.equal(smp1, smp2)

[kadyb]

Thanks for the explanation!

[kadyb]

BTW: I get:

pts = spatSample(as.polygons(r, ext=TRUE), 100)
Error: [] Cannot do this transformation
In addition: Warning message:
Cannot find coordinate operations from `ENGCRS["Cartesian (Meter)",EDATUM[""],CS[Cartesian,2],AXIS["(E)",east,ORDER[1],LENGTHUNIT["metre",1,ID["EPSG",9001]]],AXIS["(N)",north,ORDER[2],LENGTHUNIT["metre",1,ID["EPSG",9001]]]]' to `EPSG:4326' (GDAL error 6) 

I have GDAL 3.5.2 and terra 1.6.38.

Edit: This works in terra 1.6.17. This is regression from #797.

[rhijmans]

Thanks. That is because I changed the crs to "local". It works now, albeit with a warning.