I am plotting spatial data on transparent backgrounds for overlay on top of
a GoogleMaps interface but they aren't *exactly* right.

I have set the size of GoogleMaps and my image to 640X640 and I receive
bounds information on the current region from the GoogleMaps javascript API.

The problem is that the image generated by spplot does not strictly adhere
to the xlim and ylim parameters I am passing in.

As an example, here is some debugging of a plot of watershed basins

  print(paste("map_west = ",w,", map_east =",e,", map_south = ",s,",
map_north = ",n))
  xlim = c(w,e)
  ylim = c(s,n)
  plot(basin,xlim=xlim,ylim=ylim,border=col_basin,lwd=lwd_basin)
  print(paste("usr_west = ",format(par()$usr[1],digits=7,nsmall=4),",
usr_east =",format(par()$usr[2],digits=7,nsmall=4),
              ", usr_south = ",format(par()$usr[3],digits=6,nsmall=4),",
usr_north = ",format(par()$usr[4],digits=6,nsmall=4)))

And here is the resulting text output:

[1] "map_west =  -124.4348 , map_east = -123.6252 , map_south =  43.8856 ,
map_north =  44.4652"
[1] "usr_west =  -124.4672 , usr_east = -123.5928 , usr_south =  43.8618 ,
usr_north =  44.4890"


Things are close but not *exactly* right. Is there anything I can do to
force spplot to stick to the boundaries I have passed in?

I am using R 2.13.1 and sp 0.9-85.

Thanks in advance.

-- 
Jonathan Callahan, PhD
Mazama Science
206-708-5028
mazamascience.com

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