writeOGR to GPX file: empty table
On Mon, 17 May 2010, Agustin Lobo wrote:
Hi!, I'm converting from shape to gpx through rgdal (I get an empty file with gpsbabel and, according to its web, I'm not convinced that the shape format is actually fully supported by gpsbabel). This is what I do:
AilantMSY09 <- readOGR(dsn="/media/TRANSCEND/MONTSENY2008/MONTSENY_GEODATA/FloraExotica2009/AilantMSY09/",layer="AilantMSY09")
OGR data source with driver: ESRI Shapefile
writeOGR(AilantMSY09, dsn="/media/TRANSCEND/MONTSENY2008/MONTSENY_GEODATA/FloraExotica2009/AilantMSY09GPX",layer="AilantMSY09GPX",driver="GPX")
Error in writeOGR(AilantMSY09, dsn = "/media/TRANSCEND/MONTSENY2008/MONTSENY_GEODATA/FloraExotica2009/AilantMSY09GPX", : GDAL Error 6: Field of name 'Comentario' is not supported in GPX schema. Use GPX_USE_EXTENSIONS creation option to allow use of the <extensions> element. After reading the gdal-ogr doc, I include dataset_options:
writeOGR(AilantMSY09, dsn="/media/TRANSCEND/MONTSENY2008/MONTSENY_GEODATA/FloraExotica2009/AilantMSY09GPX",layer="AilantMSY09GPX",driver="GPX",dataset_options="GPX_USE_EXTENSIONS=YES")
Error in writeOGR(AilantMSY09, dsn = "/media/TRANSCEND/MONTSENY2008/MONTSENY_GEODATA/FloraExotica2009/AilantMSY09GPX", : GDAL Error 1: Latitude 4627933.603181 is invalid. Valid range is [-90,90]. This warning will not be issued any more Which indicates that the user must unproject first (it seems that GPX files only support lon,lat):
AilantMSY09WGS84LL <- spTransform(AilantMSY09, CRS("+proj=longlat
+ellps=WGS84"))
Warning message: In spTransform(xSP, CRSobj) : Only x- and y-coordinates are being transformed
writeOGR(AilantMSY09WGS84LL, dsn="/media/TRANSCEND/MONTSENY2008/MONTSENY_GEODATA/FloraExotica2009/AilantMSY09GPX.gpx",layer="AilantMSY09GPX",driver="GPX",dataset_options="GPX_USE_EXTENSIONS=YES")
Once in QGIS, the points are in the right sites but the attribute table is all NULLs
Please check the output GPX file in a text editor to see what is present there. Also please read the GPX file back into R with readOGR(), assuming that on your platform the OGR GPX driver has read support. Roger
This is not a concern (by now) for me as I just need the gpx file to upload the points to the gps unit, but report it just in case this is a bug and/or to know if I'm doing something wrong. Note: I do get the correct table for the gpx file using plugin OGR converter in QGIS. Thanks Agus
Roger Bivand Economic Geography Section, Department of Economics, Norwegian School of Economics and Business Administration, Helleveien 30, N-5045 Bergen, Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43 e-mail: Roger.Bivand at nhh.no