On 12/19/11 4:47 PM, Stefan Mertl wrote:
Hi Jeff,
I'm not an expert in coordinate transformation and the usage of proj, so
I can't exactly tell you if I have all the datum files installed. If you
could tell me what files could be missing I could search for them.
What makes me wonder, is that you get the results that my
mpl_toolkits.basemap.pyproj.Proj usage produced. When using some
conversion tools on the internet like
http://home.hiwaay.net/~taylorc/toolbox/geodesy/datumtrans/ or
http://www.uwgb.edu/dutchs/UsefulData/ConvertUTMNoOZ.HTM
I get the results that my commandline proj produces.
So I think that something with my pyproj installation is not working.
Regards,
Stefan.
Stefan: I mis-spoke in my earlier email - the answer I get with pyproj
is the same as you get with command line proj. What version of basemap
do you have installed?
-Jeff
Am Montag, den 19.12.2011, 15:51 -0700 schrieb Jeff Whitaker:
On 12/19/11 2:23 PM, Stefan Mertl wrote:
Hello,
I'm starting to use the mpl_toolkits.basemap.pyproj.Proj class to do
lon/lat to UTM coordinate conversion.
I did some tests and noticed that there is a discrepancy between the
mpl_toolkits.basemap.pyproj.Proj output and the proj commandline tool
output.
e.g.: I'm converting the coordinates lat=48.2; lon=16.5 to UTM
coordinates UTM zone 33 with WGS84 ellipse.
I'm using the following proj4 string for the conversion:
+proj=utm +zone=33 +ellps=WGS84 +datum=WGS84 +units=m +no_defs
The output using mpl_toolkits.basemap.pyproj.Proj is:
x: 611458.865; y: 5339596.032
The proj commandline tool using the same proj4 string gives:
x: 611458.69 y: 5339617.54
As you can see, the y coordinate differs significantly.
Here's the code used with the basemap pyproy classes:
--------------------------------------------------
from mpl_toolkits.basemap.pyproj import Proj
# I got the proj string from
# http://spatialreference.org/ref/epsg/32633
myProj = Proj("+proj=utm +zone=33 +ellps=WGS84 +datum=WGS84 +units=m
+no_defs")
lat = 48.2
lon = 16.5
(x,y) = myProj(lon, lat)
print "x: %.3f; y: %.3f" % (x,y)
---------------------------------------------------
Can somebody explain me this behavior?
Regards,
Stefan.
Stefan:
When I run this test, I get the same answer with both, and it is the
same as the answer basemap.pyproj gave you. I suspect you didn't
install the extra datum files with your command-line proj distribution.
-Jeff
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