convUL: wrong for Southern hemisphere
On Sat, 3 Nov 2007, Agustin Lobo wrote:
Dear list,
For negative latitudes (Southern hemisphere), convUL yields negative UTM
coordinates as
for Northern hemisphere, instead of positive UTMY coordinates for the
South. I don't see any option for modifying this behavior, is it?
The same is true for spTransform, can't fnd the way of stating that
the utm zone is in the Southern hemisphere (which should not be
required, because of the negative latitude)
spTransform(tomas1sp, CRS("+proj=utm +zone=19 +ellps=WGS84"))
yields negative UTMY coordinates and
spTransform(tomas1sp, CRS("+proj=utm +zone=-19 +ellps=WGS84"))
Well, it is an error. It is not accepted that a negative zone number is what is needed to add the y offset. In PROJ.4 notation, you simply add +south to the definition:
library(rgdal)
CRS("+init=epsg:32719")
CRS arguments: +init=epsg:32719 +proj=utm +zone=19 +south +ellps=WGS84 +datum=WGS84 +units=m +no_defs +towgs84=0,0,0 Details at: http://www.remotesensing.org/geotiff/proj_list/transverse_mercator.html Other notations may vary, but just assuming that minus indicates south is overoptimistic. Roger
an error 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