DKRZ PyNGL map tickmark example Lambert Conformal projectionΒΆ

Example script:

#
#  File:
#    mptick_9.py
#
#  Synopsis:
#    Demonstrates how to explicitly label the axes with the tickmarks and labels you want.
#    You can use this for rectangular map projections only.
#
#  Categories:
#    map plot
#
#  Based on NCL example:
#    mptick_9.ncl
#
#  Author:
#    Karin Meier-Fleischer
#
#  Date of initial publication:
#    November 2018
#
#  Description:
#    This example shows how to create a map.
#
#  Effects illustrated:
#    o  Explicitly setting map tickmarks and labels
#    o  Attaching a plot as an annotation of another plot
#    o  Drawing a lambert conformal map
#    o  Drawing a mercator map
#    o  Maximizing plots after they've been created
#    o  Converting NDC values to lat/lon values
#    o  Using "get_float" to retrieve the size of a plot
#    o  Creating a blank plot
#    o  Drawing a map using the medium resolution map outlines
#    o  Moving the main title up
#
#  Output:
#    A single visualization is produced.
#
'''
  PyNGL Example:     mptick_9.py

  -  Explicitly setting map tickmarks and labels
  -  Attaching a plot as an annotation of another plot
  -  Drawing a lambert conformal map
  -  Drawing a mercator map
  -  Maximizing plots after they've been created
  -  Converting NDC values to lat/lon values
  -  Using "get_float" to retrieve the size of a plot
  -  Creating a blank plot
  -  Drawing a map using the medium resolution map outlines
  -  Moving the main title up

'''
from __future__ import print_function
import numpy as np
import Ngl

#-------------------------------------------------------
# Function to attach lat/lon labels to a Robinson plot
#-------------------------------------------------------
def add_labels(wks,map,dlat,dlon):

    #-- generate lat/lon values
    dla = (180.0/dlat)+1                  #-- number of lat labels
    dlo = (360.0/dlon)+1                  #-- number of lon lables

    lat_values = np.linspace( -90.0,  90.0, dla, endpoint=True)
    lon_values = np.linspace(-180.0, 180.0, dlo, endpoint=True)
    nlat       = len(lat_values)
    nlon       = len(lon_values)

    #-- assign arrays to hold the labels
    lft, rgt                     = [],[]
    lat_lft_label, lat_rgt_label = [],[]
    lon_bot_label                = []

    #-- text resources
    txres               = Ngl.Resources()
    txres.txFontHeightF = 0.01

    #-- add degree sign and S/N to the latitude labels
    #-- don't write 90S label which would be too close to the lon labels
    for l in lat_values:
        if l == -90.0:
           lat_lft_label.append("".format(l))
           lat_rgt_label.append("".format(l))
        elif l < 0:
           lat_lft_label.append("{}~S~o~N~S    ".format(np.fabs(l)))
           lat_rgt_label.append("    {}~S~o~N~S".format(np.fabs(l)))
        elif l > 0:
           lat_lft_label.append("{}~S~o~N~N    ".format(l))
           lat_rgt_label.append("    {}~S~o~N~N".format(l))
        else:
           lat_lft_label.append("0  ")
           lat_rgt_label.append("   0")

    #-- add degree sign and W/E to the longitude labels
    for l in lon_values:
        if l < 0:
           lon_bot_label.append("{}~S~o~N~W".format(np.fabs(l)))
        elif l > 0:
           lon_bot_label.append("{}~S~o~N~E".format(l))
        else:
           lon_bot_label.append("0")

    #-- add the latitude labels left and right to the plot
    for n in range(0,nlat):
       txres.txJust = "CenterRight"
       lft.append(Ngl.add_text(wks,map,lat_lft_label[n],-180.0,\
                                        lat_values[n],txres))
       txres.txJust = "CenterLeft"
       rgt.append(Ngl.add_text(wks,map,lat_rgt_label[n],180.0,\
                                         lat_values[n],txres))
    #-- add the longitude labels at the bottom of the plot
    bot = []
    for n in range(0,nlon):
       txres.txJust = "TopCenter"
       bot.append(Ngl.add_text(wks,map,lon_bot_label[n],lon_values[n],\
                                        -90.0,txres))
    return

#-----------------------------------------------------------------------
#-- Function: main
#-----------------------------------------------------------------------
def main():

    #-------------------------------------------------------
    #                       MAIN
    #-------------------------------------------------------
    wks = Ngl.open_wks("png","plot_mptick_9")               #-- open workstation

    #-----------------------------------
    #-- first plot: Lambert Conformal
    #-----------------------------------
    mpres                        =  Ngl.Resources()         #-- resource object
    mpres.nglDraw                =  False                   #-- turn off plot draw and frame advance. We will
    mpres.nglFrame               =  False                   #-- do it later after adding subtitles.

    mpres.mpFillOn               =  True                    #-- turn map fill on
    mpres.mpOutlineOn            =  False                   #-- outline map
    mpres.mpOceanFillColor       = "Transparent"            #-- set ocean fill color to transparent
    mpres.mpLandFillColor        = "Gray90"                 #-- set land fill color to gray
    mpres.mpInlandWaterFillColor = "Gray90"                 #-- set inland water fill color to gray

    mpres.tiMainString           = "Lambert Conformal Map"
    mpres.tiMainOffsetYF         =  0.05

    mpres.mpProjection           = "LambertConformal"
    mpres.mpLambertParallel1F    =  10
    mpres.mpLambertParallel2F    =  70
    mpres.mpLambertMeridianF     = -100
    mpres.mpLimitMode            = "LatLon"
    mpres.mpMinLatF              =  20
    mpres.mpMaxLatF              =  55
    mpres.mpMinLonF              = -140
    mpres.mpMaxLonF              = -60
    mpres.mpGridAndLimbOn        =  True
    mpres.mpGridSpacingF         =  10.

    mpres.pmTickMarkDisplayMode  = "Always"

    #-- create and draw the basic map
    map = Ngl.map(wks,mpres)

    #-- add labels to the plot
    tx = add_labels(wks,map,30,90)

    #-- draw the plot and advance the frame
    Ngl.draw(map)
    Ngl.frame(wks)

    del(mpres)  #-- delete resource object

    #-----------------------------------
    #-- second plot: Mercator projection
    #-----------------------------------
    mpres                        =  Ngl.Resources()
    mpres.nglDraw                =  False                   #-- turn off plot draw and frame advance. We will
    mpres.nglFrame               =  False                   #-- do it later after adding subtitles.

    mpres.tiMainString           = "Mercator Map"           #-- title
    mpres.tiMainFontHeightF      =  0.020                   #-- increase font size

    mpres.mpFillOn               =  False                   #-- turn off land fill
    mpres.mpDataBaseVersion      = "MediumRes"              #-- use finer database
    mpres.mpProjection           = "mercator"               #-- projection
    mpres.mpLimitMode            = "Corners"                #-- method to zoom
    mpres.mpLeftCornerLatF       =   32
    mpres.mpLeftCornerLonF       =  128
    mpres.mpRightCornerLatF      =   55
    mpres.mpRightCornerLonF      =  144

    mpres.pmTickMarkDisplayMode  = "Always"                 #-- turn on tickmarks

    #-- create and draw the basic map
    map = Ngl.map(wks,mpres)

    #-- maximize the plot, draw it and advance the frame
    Ngl.maximize_plot(wks,map)
    Ngl.draw(map)
    Ngl.frame(wks)

    Ngl.end()

if __name__ == '__main__':
    main()

Result:

PyNgl mptick 9 w400