I tried to polygon.....you are right...too slow I'm not sure how to resample to get a regular grid...using interp or interpp would not be wise because of the size of the grid...
On Mon, Jul 13, 2009 at 11:09 AM, Barry Rowlingson < b.rowling...@lancaster.ac.uk> wrote: > 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 > -- Matthew J. Oliver Assistant Professor School of Marine Science and Policy College of Earth, Ocean and Environment University of Delaware 700 Pilottown Rd. Lewes, DE, 19958 302-645-4079 http://www.ceoe.udel.edu/people/profile.aspx?moliver [[alternative HTML version deleted]] _______________________________________________ R-sig-Geo mailing list R-sig-Geo@stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo
