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I am trying to render a polygon using python matplot Basemap lib.

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

def render_polygon(lat, long):
  map = Basemap(llcrnrlon=-10,llcrnrlat=35,urcrnrlon=35,urcrnrlat=60.,
                                  resolution=None, projection='tmerc', lat_0 =
                                  8.30, lon_0 = 3.46)
  map.plot(lat, long, marker=None,color='m')
  plt.show()

lat = [56.1304, 55.1304, 54.1304, 53.1304, 52.1304]
long = [106.3468, 107.3468, 105.3468, 104.3468, 103.3468]
render_polygon(lat, long)

When I run the program passing the latitude longitude I see an empty rectangle. Can someone point out what am I doing incorrect?

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2
  • Please show the data (lat, long), including the lines of code that make use of render_polygon(). Commented Mar 24, 2020 at 13:26
  • @swatchai updated the data that uses render_polygon Commented Mar 28, 2020 at 21:50

1 Answer 1

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1

You need to transform coordinates in the process. Try changing

map.plot(lat, long, marker=None, color='m')

to

map.plot(*map(long, lat), marker=None, color='m')

The code *map(long, lat) does the required coordinate transformation, and spreads the result to xs, ys in that place.

Edit 1

The original code have been edited to get appropriate data extent, proper projection parameters.

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

def render_polygon(lat, long):
  map = Basemap(llcrnrlon=103, llcrnrlat=50, urcrnrlon=107.5, urcrnrlat=60.,
                resolution='c', projection='merc', 
                lat_0 = 50, lon_0 = 105)
  map.plot(*map(long, lat), marker=None, color='m')
  #map.drawcoastlines(linewidth=0.7)
  plt.show()

lat = [56.1304, 55.1304, 54.1304, 53.1304, 52.1304]
long = [106.3468, 107.3468, 105.3468, 104.3468, 103.3468]
render_polygon(lat, long)

The output plot:

enter image description here

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