[R-sig-Geo] kernel density estimation to google earth

[Marco Helbich]

Dear List,

I've calculated a kernel density estimation (splancs function) and now I 
want to export the result as a kml-file to open it in the google earth 
viewer, but I get stuck at converting the SpatialGridDataFrame to a 
SpatialPixelDataFrame...

here (http://www.zshare.net/download/689742375ef5fb/) you can download some 
testdata and my R-code so far:

###########
data.shp <- readOGR("C:/", layer="events")
prj <- data.shp@ proj4string@ projargs
dat <- data.shp
str(dat)
poly.shp <- readOGR("C:/", layer="hull")
str(poly.shp)

dat.SP <- as(dat, "SpatialPoints")
str(dat.SP)
pp_poi <- as.points(dat.SP at coords[,1], dat.SP at coords[,2])
poly <- 
getPolygonCoordsSlot(getPolygonsPolygonsSlot(getSpPpolygonsSlot(poly.shp)[[1]])[[1]])
polymap(poly)
points(pp_poi)

grd <- GridTopology(cellcentre.offset=c(590511, 396191), cellsize=c(2000, 
2000),
  cells.dim=c(30,25))
kbw2000 <- spkernel2d(pp_poi, poly, h0=2000, grd)
spplot(SpatialGridDataFrame(grd, data=data.frame(kbw2000)), 
col.regions=terrain.colors(16))

test <- SpatialGridDataFrame(grd, data=data.frame(kbw2000))
proj4string(test) <- CRS(prj)
str(test)
test1 <- spTransform(test, CRS("+proj=longlat +datum=WGS84"))

## here I got following error message:
# validityMethod(as(object, superClass)): Geographical CRS given to 
non-conformant data
test2 <- spsample(test1, type="regular", cellsize=c(2000,2000))

# export the SpatialPixelDataFrame (Code (not testet) from the help-file)
tf <- tempfile()
SGxx <- GE_SpatialGrid(test2)
png(file=paste(tf, ".png", sep=""), width=SGxx$width, height=SGxx$height,
  bg="transparent")
par(mar=c(0,0,0,0), xaxs="i", yaxs="i")
plot(x, xlim=SGxx$xlim, ylim=SGxx$ylim, setParUsrBB=TRUE)
dev.off()
kmlOverlay(SGxx, paste(tf, ".kml", sep=""), paste(tf, ".png", sep=""))
###########

I appreciate every hint! Thanks.
Marco

-- 
Marco Helbich
Institute for Urban and Regional Research
Austrian Academy of Sciences
Postgasse 7/4/2, A-1010 Vienna, Austria (EU)
e-mail: marco.helbich(at)oeaw.ac.at