# How to plot a heatmap (gridded data) on a global map with cartopy in python ?

Published: October 13, 2021

Updated: December 09, 2022

Tags: Python; Cartopy;

Examples of how to plot a heatmap on a global map with cartopy in python

## Get gridded data

Let's first get some data:

````import numpy as np`

`data = np.loadtxt('https://raw.githubusercontent.com/benjamin-hg-marchant/teaching/main/datasets/modis_myd06_cpop_2d_hist_1b1_grid.txt')`
```

Note that

````data.shape`
```

gives

````(360, 180)`
```

Here longitude [-180,180] are on the first axis (axis =0) and latitude [-90: 90] on the second axis (axis =1):

## Plot a simple map with cartopy

````from cartopy import config`
`from matplotlib.pyplot import figure`

`import cartopy.crs as ccrs`
`import matplotlib.pyplot as plt`

`fig = plt.figure(num=None, figsize=(8, 6), dpi=80, edgecolor='k')`

`ax = plt.axes(projection=ccrs.PlateCarree())`

`ax.coastlines()`

`plt.title("Plot a global map with cartopy in python", fontsize=12)`

`plt.savefig("cartopy_heatmap_01.png", bbox_inches='tight', dpi=200)`
```

## Plot a heatmap with cartopy

````from cartopy import config`
`from matplotlib.pyplot import figure`

`import cartopy.crs as ccrs`
`import matplotlib.pyplot as plt`

`fig = plt.figure(num=None, figsize=(8, 6), dpi=80, edgecolor='k')`

`ax = plt.axes(projection=ccrs.PlateCarree())`

`ax.imshow(data.T, origin='lower', extent=[-180,180,-90,90], transform=ccrs.PlateCarree(),cmap='jet',vmin=0, vmax=1.0)`

`ax.coastlines()`

`plt.title("Plot a heatmap with cartopy in python", fontsize=12)`

`plt.savefig("cartopy_heatmap_02.png", bbox_inches='tight', dpi=200)`
```

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