On 4/2/12 11:23 AM, Jeff Whitaker wrote:
On 4/2/12 10:03 AM, Mathew Topper wrote:
On 02/04/12 16:21, Jeff Whitaker wrote:
On 4/2/12 9:10 AM, Mathew Topper wrote:
Hi,
I've been trawling round the internet for a while trying to work
out if basemap could be made to plot using a UTM zone projection.
I've found some references to pyproj that could be used to convert
out of a UTM projection, but I haven't found any references to
defining a custom projection for basemap. Is it possible?
Also, there is not a lot of documentation regarding pyproj and I
find this a little odd considering it comes packaged with basemap.
Many Thanks,
Mat
Mat: Basemap can plot in the tranverse mercator projection
(projecton='tmerc') - UTM zones are transverse mercator with
specific lat/lon boundaries and a WGS84 ellipsoid. I suppose I could
add UTM zone support if there is enough demand for it.
-Jeff
--
Jeffrey S. Whitaker Phone : (303)497-6313
Meteorologist FAX : (303)497-6449
NOAA/OAR/PSD R/PSD1 Email :jeffrey.s.whita...@noaa.gov
325 Broadway Office : Skaggs Research Cntr 1D-113
Boulder, CO, USA 80303-3328 Web :http://tinyurl.com/5telg
OK, thanks Jeff. So I just need to know the lon/lat bounds of the
desired UTM zone and I have effectively created a UTM projection of
that zone in basemap i.e. for UTM29 we have 12W to 6W.
Will basemap then except coordinates in meters defined by UTM29 or do
I have to convert to lon/lat first?
Mat: If you use projection='tmerc' and then give the lat/lon coords
of the upper right and lower left corners with
llcrnrlon,llcrnrlat,urcrnrlon,urcrnrlat, the projection coordinates
will be such that x,y = 0 in the lower left corner. Since those will
not match the UTM coordinates exactly, you will have to add an offset
in x,y to make them match.
-Jeff
Mat: I just updated git master to add the 'k_0' keyword when using
projection='tmerc'. This is the scaling factor along the central
meridian, and is needed to exactly match the UTM definition. I also
added a utmtest.py example, that shows how to plot a UTM zone, and
convert Basemap coordinates to UTM coordinates.
-Jeff
--
Jeffrey S. Whitaker Phone : (303)497-6313
Meteorologist FAX : (303)497-6449
NOAA/OAR/PSD R/PSD1 Email : jeffrey.s.whita...@noaa.gov
325 Broadway Office : Skaggs Research Cntr 1D-113
Boulder, CO, USA 80303-3328 Web : http://tinyurl.com/5telg
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