INTAMAP--->GeoTIFF

Hey,

After checking the vignette of Intamap, you can find out from this 
example that

data(meuse)
coordinates(meuse) = ~x+y
meuse$value = meuse$zinc
data(meuse.grid)
gridded(meuse.grid) = ~x+y
x = interpolate(meuse, meuse.grid, list(mean=TRUE, variance=TRUE))

x$predictions is a SpatialPixelsDataFrame which can easily be writen 
into a Geotiff with writeGDAL

str(x$predictions)
Formal class 'SpatialPixelsDataFrame' [package "sp"] with 7 slots
   ..@ data       :'data.frame': 3103 obs. of  2 variables:
   .. ..$ var1.pred: num [1:3103] 855 918 831 745 988 ...
   .. ..$ var1.var : num [1:3103] 42417 32710 35528 38716 22472 ...
   ..@ coords.nrs : num(0)
   ..@ grid       :Formal class 'GridTopology' [package "sp"] with 3 slots
   .. .. ..@ cellcentre.offset: Named num [1:2] 178460 329620
   .. .. .. ..- attr(*, "names")= chr [1:2] "x" "y"
   .. .. ..@ cellsize         : Named num [1:2] 40 40
   .. .. .. ..- attr(*, "names")= chr [1:2] "x" "y"
   .. .. ..@ cells.dim        : Named int [1:2] 78 104
   .. .. .. ..- attr(*, "names")= chr [1:2] "x" "y"
   ..@ grid.index : int [1:3103] 69 146 147 148 223 224 225 226 300 301 ...
   ..@ coords     : num [1:3103, 1:2] 181180 181140 181180 181220 181100 ...
   .. ..- attr(*, "dimnames")=List of 2
   .. .. ..$ : NULL
   .. .. ..$ : chr [1:2] "x" "y"
   ..@ bbox       : num [1:2, 1:2] 178440 329600 181560 333760
   .. ..- attr(*, "dimnames")=List of 2
   .. .. ..$ : chr [1:2] "x" "y"
   .. .. ..$ : chr [1:2] "min" "max"
   ..@ proj4string:Formal class 'CRS' [package "sp"] with 1 slots
   .. .. ..@ projargs: chr NA

Watch out that the projection is not defined.
I guess that writeGDAL(x$predictions, ....) with appropriate file name 
and driver should do the trick

HTH

Alex