[R-sig-Geo] sp::overlay problem

piero campa piero.campa at gmail.com
Tue Apr 12 15:04:58 CEST 2011

Dear list,
I have a SpatialGridDataFrame, whose SRS is EPSG:32632:
"+init=epsg:32632 +proj=utm +zone=32 +ellps=WGS84 +datum=WGS84 +units=m
+no_defs +towgs84=0,0,0"

I am willing to overlay these grid values over point locations defined in a
SpatialPixelsDataFrame with a different SRS using the overlay method
(overlaying grids over points in the same SRS gave me no problem until now).

Now instead I need to transform the point locations to EPSG:32632 and then
> my.ov <- overlay(my.grid, spTransform(mySpatialPixels,
> CRS=CRS(proj4string(my.grid))))
[looking at methods?sp::overlay, transforming the grid to the points SRS
would coerce the grid itself into points, and then the overlay method would
not be useful anymore]

But then the output "my.ov" is filled with NAs only.

I checked the bbox of the overlay inputs, and they overlap:
> bbox(my.grid)
              min     max
coords.x1  513000  911000
coords.x2 4844000 5002000
> bbox(mySpatialPixels)
        min       max
x  499880.9  822436.4
y 4816908.3 5045694.8

Any hint is appreciated.
Thank you guys.


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