[R-sig-Geo] gIntersection error in rgeos package

[maogui.hu]

Hi all,
I found a problem when using the "gIntersection" in rgeos for two lines. The expected result is a long line shared by two lines. However, the result I obtained is a short line (a part of the afore mentioned long line). I have tried to change the setScale() value for different operation precision. But the result is almost the same. I think may be it is a bug of the function. Attached are the data, r code and results. Can anybody help me to solve it? thanks very much.

require(maptools)
require(rgeos)

ws <- "E:/testdata/"
sline1 <- readShapeLines(file.path(ws, "Line01.shp"))
sline2 <- readShapeLines(file.path(ws, "Line02.shp"))

Intersection <- function(line1, line2)
{
gL <- c()
nLength <- 0
for(s in 10^c(-2:8))
{
setScale(s)
gL0 <- gIntersection(line1, line2)
if(gLength(gL0) > nLength) 
{
gL <- gL0
nLength <- gLength(gL)
}
}
setScale()
return(gL)
}

par(mfrow=c(2,2))
plot(sline1, col="red")
plot(sline2, col="blue")
plot(rbind.SpatialLines(sline1, sline2, makeUniqueIDs=TRUE), col=c("red","blue"))
rslt <- Intersection(sline1, sline2)
plot(rslt, col="green")




maogui.hu
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