Patrick,

I have had some success with plotting sp objects on top of G maps with
this function


gmap <- function(xy, maptype='terrain', ...) {
    require(RgoogleMaps)
        fun = points
        if (inherits(xy, 'Spatial')) {
                b = bbox(xy)
                if (inherits(xy, 'SpatialPoints')) {
                        xy = coordinates(xy)
                } else {
                        x = unlist(lapply(x...@polygons, function(i)slot(i, 
'Polygons')))
                        x = lapply(x, function(x)slot(x, 'coords'))
                        xy = matrix(ncol=2, nr=0)
                        for (i in 1:length(x)) xy = rbind(xy, x[[i]], c(NA,NA))
                        fun = lines
                }
        } else {
                b = rbind(range(xy[,1], na.rm=TRUE), range(xy[,2], na.rm=TRUE))
        }
        mykey <-  ### fill in your google maps API key for http://localhost/
    gm <- GetMap.bbox(key=localhostkey, lonR=b[1,], latR=b[2,], maptype=maptype)
    tmp <- PlotOnStaticMap(gm, lon=xy[,1], lat=xy[,2], FUN=fun, verbose=0, ... )
}


a = matrix(runif(100)*100-50, ncol=2)
gmap(a)

library(sp)
gmap(SpatialPoints(a), col='red', cex=2, pch='+')

library(maptools)
data(wrld_simpl)
hti = wrld_simpl[wrld_simpl$ISO3=='HTI',]
gmap(hti, lwd=2, col='red')


Hth,
Robert


On Sat, Jan 16, 2010 at 5:35 PM, Patrick Crutcher <pcrutc...@gmail.com> wrote:
> I have some shapefiles I want to plot over Google Maps tiles. I have
> polygons, lines and point data. What's the most efficient way to do this?
> One path might be to use the pkg RgoogleMaps, however, it is still unclear
> to me how to do this. I assume using PlotonStaticMap with some combination
> of reformatting the shapefile data. Thanks.
>
> P.
>
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