# Meridians not show using Mercator projection

Hi,

Using the example code shown below I can’t get meridians plotted on the screen:

from mpl_toolkits.basemap import Basemap

import matplotlib.pyplot as plt

import numpy as np

m = Basemap(projection=‘merc’,lon_0=-79, lat_0=25.5,

llcrnrlon=-93, urcrnrlon=-63, llcrnrlat=14, urcrnrlat=36.2)

m.drawcoastlines(linewidth=0.3)

parallels = np.arange(0.,90,2.)

m.drawparallels(parallels, labels=[1,0,0,0])

meridians = np.arange(180.,360.,5.)

m.drawmeridians(meridians, labels=[0,0,0,1])

plt.show()

Two other projections “laea” and “tmerc” work fine for this case.

Any ideas?

Thanks.

···

Gökhan

Hi,

Using the example code shown below I can't get meridians plotted on the
screen:

from mpl_toolkits.basemap import Basemap
import matplotlib.pyplot as plt
import numpy as np

m = Basemap(projection='merc',lon_0=-79, lat_0=25.5,
llcrnrlon=-93, urcrnrlon=-63, llcrnrlat=14, urcrnrlat=36.2)

m.drawcoastlines(linewidth=0.3)
parallels = np.arange(0.,90,2.)
m.drawparallels(parallels, labels=[1,0,0,0])
meridians = np.arange(180.,360.,5.)

It can't handle the wrap; subtract 360 from your meridians, and they will show up.

Eric

···

On 11/16/2011 03:16 PM, Gökhan Sever wrote:

m.drawmeridians(meridians, labels=[0,0,0,1])

plt.show()

Two other projections "laea" and "tmerc" work fine for this case.

Any ideas?

Thanks.

--
Gökhan

------------------------------------------------------------------------------
All the data continuously generated in your IT infrastructure
contains a definitive record of customers, application performance,
security threats, fraudulent activity, and more. Splunk takes this
data and makes sense of it. IT sense. And common sense.
http://p.sf.net/sfu/splunk-novd2d

_______________________________________________
Matplotlib-users mailing list
Matplotlib-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/matplotlib-users

G�khan: The longitudes in your projection definition are negative (-93 to -63), so you need to change

meridians = np.arange(180.,360.,5.)

to

meridians = np.arange(-180.,0.,5.)

It works for the other projections, since the values get transformed to projection coordinates anyway. With merc and cyl, there is no transformation for longitudes.

-Jeff

···

On 11/16/11 6:16 PM, G�khan Sever wrote:

from mpl_toolkits.basemap import Basemap
import matplotlib.pyplot as plt
import numpy as np

m = Basemap(projection='merc',lon_0=-79, lat_0=25.5,
llcrnrlon=-93, urcrnrlon=-63, llcrnrlat=14, urcrnrlat=36.2)

m.drawcoastlines(linewidth=0.3)
parallels = np.arange(0.,90,2.)
m.drawparallels(parallels, labels=[1,0,0,0])
meridians = np.arange(180.,360.,5.)
m.drawmeridians(meridians, labels=[0,0,0,1])

plt.show()

Two other projections "laea" and "tmerc" work fine for this case.

Any ideas?

Thanks.

--
G�khan

Thanks Jeff and Eric.

Both solutions simply works

···

Gökhan

Hi,

Using the example code shown below I can't get meridians plotted on the
screen:

from mpl_toolkits.basemap import Basemap
import matplotlib.pyplot as plt
import numpy as np

m = Basemap(projection='merc',lon_0=-79, lat_0=25.5,
llcrnrlon=-93, urcrnrlon=-63, llcrnrlat=14, urcrnrlat=36.2)

m.drawcoastlines(linewidth=0.3)
parallels = np.arange(0.,90,2.)
m.drawparallels(parallels, labels=[1,0,0,0])
meridians = np.arange(180.,360.,5.)

It can't handle the wrap; subtract 360 from your meridians, and they
will show up.

I just committed a fix for this, so that the wraparound is handled automatically in drawmeridians.

-Jeff

···

On 11/16/11 8:00 PM, Eric Firing wrote:

On 11/16/2011 03:16 PM, Gökhan Sever wrote:

Eric

m.drawmeridians(meridians, labels=[0,0,0,1])

plt.show()

Two other projections "laea" and "tmerc" work fine for this case.

Any ideas?

Thanks.

--
Gökhan

--
Jeffrey S. Whitaker Phone : (303)497-6313
Meteorologist FAX : (303)497-6449
NOAA/OAR/PSD R/PSD1 Email : Jeffrey.S.Whitaker@...259...
325 Broadway Office : Skaggs Research Cntr 1D-113
Boulder, CO, USA 80303-3328 Web : http://tinyurl.com/5telg