On Mon, Jul 13, 2009 at 3:26 PM, Matt Oliver<moli...@udel.edu> wrote: > Dear r-sig-geo, > > I am trying to generate a kml for an image I am producing using image(). > After reading about kml generation, I'm unsure if I sould be using > kmlOverlay() or writeOGR, or some other function. > > This is the data > > http://www.ceoe.udel.edu/cms/moliver/20071003.276.0237.n17.nc > > require(ncdf) > require(fields) > f <- open.ncdf("20071003.276.0237.n17.nc") > > lon <- get.var.ncdf(f, "lon") > lat <- get.var.ncdf(f, "lat") > mcsst <- get.var.ncdf(f, "mcsst") > plot(diff(lon)) #####notice decreasing > par(mar=c(0, 0, 0, 0)) > par(bty="n") > > image(lon, lat, mcsst, col = tim.colors(64)) #####image I want to make kml > for > > I don't seem to be able to make a proper "Spatial" object because of the > unequally spaced geographic coordinates.This seems to be necessary to to > proceed with a kml generation. > > I'm probably missing something simple so any help or example code would be > wonderful >
KML does this kind of image overlay by taking an image file (PNG, jpeg etc) and it's bounding box in lat-long. It can't cope with irregular grids. My first thought as a workaround was to turn every pixel into a rectangular polygon. But then I got the data and saw we were dealing with 1445626 pixels and that google earth would probably crawl... So I think you'll need to resample your data onto a regular lat-long grid, then save it as an image, and then write the relevant KML with the bounds. The KML is quite simple: http://code.google.com/apis/kml/documentation/kml_tut.html#ground_overlays but the resampling might not be. I think I've written some resampling code somewhere, it just works out where in the old array a bunch of regularly spaced points are that will make the new array are, and samples. There may be R code for doing interpolation - maybe the rimage or RImageJ packages... But no, I don't think anything existing can do it [waits for Roger to prove him wrong again...]. Barry _______________________________________________ R-sig-Geo mailing list R-sig-Geo@stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo