combine spatial layers

# Get the layers from .kml file
layers <- ogrListLayers('bbmp.kml')[2:198]
i<-1
# Get polygon from first layer
poly.data <- readOGR(dsn="bbmp.kml", layer=layers[1], encoding="utf-8", verbose = F)
n <- length(slot(poly.data, "polygons"))
poly.data <- spChFIDs(poly.data, as.character(i:(i+n-1)))
i <- i + n
# Combine remaining polygons with first polygon
timer_all <- Sys.time()
pb <- txtProgressBar(max=length(layers), style = 3)
options(warn=-1) # disable warnings
for (i in 2:length(layers)) {
    temp.data <- readOGR(dsn="bbmp.kml", layer=layers[i], encoding="utf-8", verbose = F)
    n <- length(slot(temp.data, "polygons"))
    temp.data <- spChFIDs(temp.data, as.character(i:(i+n-1)))
    i <- i + n
    poly.data <- spRbind(poly.data,temp.data)
    setTxtProgressBar(pb, i)
}
cat("***Process completed in",round(difftime(Sys.time(), timer_all, tz = "", units = "mins"),2),"min!***")
options(warn = 0) # re-enable warnings
close(pb)
# save combined polygons to a single .kml file
writeOGR(poly.data, dsn="blr.kml", layer="bangalore", driver="KML")