[R-sig-Geo] how to show polygons from SHP file in Google map?
Wesley Roberts
wroberts at csir.co.za
Thu Jun 4 15:29:39 CEST 2009
Hi Jian,
Just noticing that you are using system.file, as I understand it this
command / switch is used for internally available data shipped with R
and the associated R-spatial packages. Your data, I believe will be
available on your hard disk and not from internal data packages
provided. I think the following should work, although I cant be 100%
sure
natSHP.sp <- readShapePoly("nro2.shp", package="maptools",
proj4string=CRS("+init=epsg:2166"))
Make sure that your working directory is set to the location of your
"nro2.shp" file and that you have the required packages loaded.
Hope this helps
Wesley
Wesley Roberts MSc.
Researcher: Earth Observation
Natural Resources & the Environment (NRE)
CSIR
Tel: +27 (0)21 888-2490
Fax: +27 (0)21 888-2693
"To know the road ahead, ask those coming back."
- Chinese proverb
>>> Jian Li <jli at mi.fu-berlin.de> 04/06/2009 15:02 >>>
Dear Torleif,
I just tried to produce another SpatialPolygons like nat.sp from SHP
file like this following:
natSHP.sp <- readShapePoly(system.file("nro2.shp",
package="maptools")[1], proj4string=CRS("+init=epsg:2166"))
in order to approach it in the same way for saving the information in
KML file
But it doesn't work. Do you know what's going wrong or do you have any
better idea?
The nro2.shp is under
http://jaguar.biologie.hu-berlin.de/~jian/phpMysqlGoogle/arcViewNro2/
available.
greeting,
Jian
> ########################
> ##Export e00 to Google Earth (png)##
> ########################
>
> #1: import using RArcInfo
>
> #Set the working directory to where you stored your nat.e00 data
> setwd('~/e00data') #Use your own path
>
> #load the RArcInfo library (for functions e00toavc, get.xxx)
> require(RArcInfo)
>
> #Convert the e00 to SpatialPolygons
> e00toavc('nat.e00', './nat2')
> nat.arc <- get.arcdata("./", "nat2")
> nat.pal <- get.paldata("./", "nat2")
> require(maptools) #Needed for pal2SpatialPolygons
> nat.sp <- pal2SpatialPolygons(nat.arc,
> nat.pal,
> nat.pal[[1]]$PolygonId[-1],
> dropPoly1=TRUE,
> proj4string=CRS("+init=epsg:2166"))
>
> #Transform to longlat, WGS84
> require(rgdal)
> nat2.sp <- spTransform(nat.sp, CRS("+proj=longlat +ellps=WGS84"))
>
> #Set up metadata
> GSG <- GE_SpatialGrid(nat2.sp)
>
> #Ask for the tempdir
> tmp.dir <- tempdir()
>
> #To change the resolution (and line width), change res
> res <- 5
> #Make png-file
> png(file=paste(tmp.dir, "/", "nat.png", sep=""), width=GSG$width*res,
> height=GSG$height*res,
> bg="transparent")
> par(mar=c(0,0,0,0), xaxs="i", yaxs="i")
> plot(nat2.sp, xlim=GSG$xlim, ylim=GSG$ylim, lwd = res)
> dev.off()
>
> #And make the Google earth kml-file
> kmlOverlay(SGqk, paste(tmp.dir, "/", "nat.kml", sep=""),
> paste(tmp.dir, "/", "nat.png", sep=""))
>
> #Now, see in td, and you have your kml and png.
>
>
> ###########################################
> ##Export the same data as polygons (still to Google earth)
> #The second option is to export as polygons
> #(See ?kmlPolygon in maptools)
>
> out <- sapply(slot(nat2.sp, "polygons"), function(x) { kmlPolygon(x,
> name=paste(slot(x, "ID")),
> col="transparent", lwd=5, border='black',
> description=paste(slot(x, "ID"))) })
>
> tf <- tempfile()
>
> kmlFile <- file(paste(tf, ".kml", sep=""), "w")
> cat(kmlPolygon(kmlname="MyGPoly",
> kmldescription="<i>Masterthesis</i>")$header,
> file=kmlFile, sep="\n")
> cat(unlist(out["style",]), file=kmlFile, sep="\n")
> cat(unlist(out["content",]), file=kmlFile, sep="\n")
> cat(kmlPolygon()$footer, file=kmlFile, sep="\n")
> close(kmlFile)
> #################
>
> Best wishes
> Torleif
>
>
> On Wednesday 03 June 2009 09:45:45 am Paul Hiemstra wrote:
> > Hi,
> >
> > You have to do two things, read your data and export it to a format
for
> > Google Earth.
> >
> > The Cran Spatial Taskview suggests the RArcInfo package to read the
e00
> > files into R. I'm not sure into what format they are loaded. Maybe
> > readOGR from the rgdal package can also read e00 files, depending
on the
> > GDAL/OGR version you have available.
> >
> > If you have your vector file in an R session in a SpatialPolygons
object
> > (see the sp-package), the following code shows an example how to
export
> > the data to a format that Google Earth can read:
> >
> > library(rgdal)
> > data(meuse)
> > coordinates(meuse) = ~x+y
> > proj4string(meuse) = CRS("+init=epsg:28992")
> > proj4string(meuse)
> > meuse.ll = spTransform(meuse, CRS("+proj=longlat"))
> > writeOGR(meuse.ll, "meuse.kml", "meuse.kml", driver="KML")
> >
> > I'm not sure if the RArcInfo reads the e00 file into a
SpatialPolygons
> > object (Virgillio?), or if it is easy to convert the output from
> > RArcInfo to an sp-class. rgdal always reads data into an sp-class,
but
> > I'm not sure if this supports the e00 format.
> >
> > I hope this e-mail provides you with some clues to work with,
> >
> > cheers and good luck with your thesis,
> > Paul
> >
> > Jian Li wrote:
> > > Dear r-sig-geo Members,
> > >
> > > recently, I've been trying to display the information from a e00
file
> > > (Grauss-Krüger coordinatensystem) in Google map but until now no
success.
> > >
> > > I would be very appreciated if anyone can help me to solve the
problem
> > > which directly concerns my master thesis.
> > >
> > > e00 file is under
> > > http://jaguar.biologie.hu-berlin.de/~jian/phpMysqlGoogle/nat.e00
> > > available
> > >
> > > Thank you in Advanced
> > >
> > > Best Regards,
> > > Jian
> > >
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