On Thu, 17 May 2012, Hodgess, Erin wrote:
Hello again.
I'm having a little bit of trouble with spTransform (probably I'm doing it
wrong), but here is what I'm doing:
Original data frame with UTM locations near Phuket, Thailand:
test1.df
Loc east north
1 a 748.168 602.861
2 b 754.302 615.609
proj1 <- CRS("+proj=utm +zone=47N")
Your points are 750m east and 600m north of the given projection origin.
If you meant km, set the units by adding +units=km to the proj4string.
However, this gives me:
coordinates Loc
1 (101.24, 5.44994) a
2 (101.295, 5.56496) b
which is not on Phuket, so something else is wrong here. Do you know
definitely that the input coordinates are UTM zone 47? Reversing the
eastings and northings gets a bit closer:
proj1 <- CRS("+proj=utm +zone=47N +units=km")
coordinates(test1.df) <- c("north", "east")
proj4string(test1.df) <- proj1
spTransform(test1.df, CRS("+proj=longlat +datum=WGS84"))
coordinates Loc
1 (99.9308, 6.7677) a
2 (100.046, 6.82295) b
but isn't there yet (reversed coordinate order does happen). What was the
source of the coordinates?
Roger
coordinates(test1.df) <- c("east","north")
proj4string(test1.df) <- proj1
Set up a spatial data frame
test1.df
coordinates Loc
1 (748.168, 602.861) a
2 (754.302, 615.609) b
spTransform(test1.df, CRS("+proj=longlat +datum=WGS84"))
coordinates Loc
1 (94.518, 0.00543748) a
2 (94.518, 0.00555246) b
Now the answers should be about 8 degrees north and 98 degrees East.
Any suggestions would be most appreciated.
Sincerely,
Erin
Erin M. Hodgess, PhD
Associate Professor
Department of Computer and Mathematical Sciences
University of Houston - Downtown
mailto: hodge...@uhd.edu
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Roger Bivand
Department of Economics, NHH Norwegian School of Economics,
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