On Wed, 17 Jan 2007, Albrecht Kauffmann wrote:
Hi all,
I'm faced with a problem applying the sp package: The projection argument in
readShapePoly(Shapefile,proj4string=CRS class argument)
e.g.: CRS(+proj=aea +lat_1=46 +lat_2=73 +lat_0=60 +lon_0=84 +x_0=0
+y_0=0 +ellps=clrk66 +units=m +no_defs)
doesn't have any impact on the plotted object. I also tested the simple
example:
xy = cbind(x = 2 * runif(100) - 1, y = 2 * runif(100) - 1)
plot(SpatialPoints(xy, proj4string =
CRS(+proj=longlat)),xlim=c(-1,1),ylim=c(-1,1))
looks exactly like
plot(SpatialPoints(xy, proj4string =CRS(+proj=stere +lon_0=98 +over))
or
plot(SpatialPoints(xy))
without any projection.
What I'm doing wrong?
What impact would you like? The vertical scaling adjustment for
geographical coordinates (+proj=longlat) is proportional to the distance
of the midpoint of ylim from the Equator, so in your case no adjustment
would be expected:
library(sp)
set.seed(1)
x - runif(20, -10, 10)
y - runif(20, -10, 10)
par(mfrow=c(3,2))
plot(SpatialPoints(cbind(x, y)), axes=TRUE)
plot(SpatialPoints(cbind(x, y), proj4string=CRS(+proj=longlat)),
axes=TRUE)
plot(SpatialPoints(cbind(x, y+50)), axes=TRUE)
plot(SpatialPoints(cbind(x, y+50), proj4string=CRS(+proj=longlat)),
axes=TRUE)
plot(SpatialPoints(cbind(x, y+70)), axes=TRUE)
plot(SpatialPoints(cbind(x, y+70), proj4string=CRS(+proj=longlat)),
axes=TRUE)
par(mfrow=c(1,1))
I use the latest versions of sp and rgdal.
With many thanks for any hint,
Albrecht Kauffmann
Potsdam University
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