DKRZ PyNGL map tickmark example Lambert Conformal projection#
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:
