Para Download

R GIS Function to Reverse KML Paths

R GIS Function to Reverse KML Paths

This is a function I wrote up for reversing KML-paths. The paths within a KML can be partially matched by their name-tags

## name: ReverseKmlPath 
## use: Reverse KML-pathsby matching their Name tags
## arguments: PATH_TO_DOC, the path to the KML-file
## NAME, the value of the name tag, function uses partial matching!
## Trail_xyz will be matched by rail
## requirements: KML-structure with Placemarks containing a  and a  tag
## author: Kay Cichini
## date: 01-05-2014
## license: CC-BY-NC-SA

ReverseKmlPath <- function(PATH_TO_DOC, NAMES) {
 
 require(XML)

 doc <- xmlInternalTreeParse(PATH_TO_DOC)
 
 if (xmlNamespaceDefinitions(doc)[[1]]$uri == "http://www.opengis.net/kml/2.2") {
 namespaces <- c(kml = "http://www.opengis.net/kml/2.2")
 flag <- 1
 } else {
 if (xmlNamespaceDefinitions(doc)[[1]]$uri == "http://earth.google.com/kml/2.0") { 
 namespaces <- c(kml0 = "http://earth.google.com/kml/2.0")
 flag <- 0
 } else {
 stop ("Stopped!: Check namespace issue..")
 }
 }
 
 
 for (NAME in NAMES) {
 
 if (flag) { 
 query <- paste0("//kml:Placemark[contains(kml:name,", sprintf("%s", NAME), "", ")]//kml:coordinates")
 } else {
 query <- paste0("//kml0:Placemark[contains(kml0:name,", sprintf("%s", NAME), "", ")]//kml0:coordinates")
 }

 coords <- tryCatch(getNodeSet(doc, query, namespaces), 
 error = function(e) message(paste(" Error: *", NAME, "* was NOT successfully matched ")))
 
 for (i in length(coords)) {

 #grab coordinates from node and reverse order
 rev_coord_vector <- rev(unlist(strsplit(gsub("t|n", "", xmlValue(coords[[i]])), "s")))
 rev_coord_string <- paste(rev_coord_vector, collapse = " ")

 # re-insert reversed line-string:
 xmlValue(coords[[i]]) <- rev_coord_string

 # message
 if (flag) { 
 query <- paste0("//kml:Placemark[contains(kml:name,", sprintf("%s", NAME), "", ")]//kml:name")
 } else {
 query <- paste0("//kml0:Placemark[contains(kml0:name,", sprintf("%s", NAME), "", ")]//kml0:name")
 }
 match <- xmlValue(getNodeSet(doc, query, namespaces)[[i]])
 message(paste0("matched name: ", match, " ..."))

 }
 }

 # save:
 message("Reversed paths saved to:")
 saveXML(doc, paste0(dirname(PATH_TO_DOC), "/reversed_", basename(PATH_TO_DOC)),
 prefix = newXMLCommentNode("This file was created with the R-package XML::saveXML, see: "))
}

## not run: 
tf <- tempfile(fileext = ".kml")
download.file("http://dev.openlayers.org/releases/OpenLayers-2.13.1/examples/kml/lines.kml", tf, mode = "wb")
ReverseKmlPath( PATH_TO_DOC = tf, NAMES = c("Absolute", "Relative") )

shell.exec(tf)
shell.exec(paste0(dirname(tf), "/reversed_", basename(tf)))

visit link download