Note
Click here to download the full example code
Plotting Earth relief
Plotting a map of Earth relief can use the data accessed by the
pygmt.datasets.load_earth_relief
method. The data can then be plotted
using the pygmt.Figure.grdimage
method.
import pygmt
Load sample Earth relief data for the entire globe at a resolution of 1 arc degree. The other available resolutions are show at https://docs.generic-mapping-tools.org/latest/datasets/remote-data.html#global-earth-relief-grids.
grid = pygmt.datasets.load_earth_relief(resolution="01d")
Create a plot
The pygmt.Figure.grdimage
method takes the grid
input to create a
figure. It creates and applies a color palette to the figure based upon the
z-values of the data. By default, it plots the map with the turbo CPT, an
equidistant cylindrical projection, and with no frame.
fig = pygmt.Figure()
fig.grdimage(grid=grid)
fig.show()
Out:
<IPython.core.display.Image object>
pygmt.Figure.grdimage
can take the optional argument projection
for the map. In the example below, the projection
is set as R12c
for
12 centimeter figure with a Winkel Tripel projection. For a list of available
projections, see https://docs.generic-mapping-tools.org/latest/cookbook/map-projections.html.
fig = pygmt.Figure()
fig.grdimage(grid=grid, projection="R12c")
fig.show()
Out:
<IPython.core.display.Image object>
Set a color map
pygmt.Figure.grdimage
takes the cmap
argument to set the CPT of
the figure. Examples of common CPTs for Earth relief are shown below.
A full list of CPTs can be found at https://docs.generic-mapping-tools.org/latest/cookbook/cpts.html.
Using the geo CPT:
fig = pygmt.Figure()
fig.grdimage(grid=grid, projection="R12c", cmap="geo")
fig.show()
Out:
<IPython.core.display.Image object>
Using the relief CPT:
fig = pygmt.Figure()
fig.grdimage(grid=grid, projection="R12c", cmap="relief")
fig.show()
Out:
<IPython.core.display.Image object>
Add a color bar
The pygmt.Figure.colorbar
method displays the CPT and the associated
Z-values of the figure, and by default uses the same CPT set by the cmap
argument for pygmt.Figure.grdimage
. The frame
argument for
pygmt.Figure.colorbar
can be used to set the axis intervals and
labels. A list is used to pass multiple arguments to frame
. In the
example below, a2500
sets the axis interval to 2,500, x+lElevation
sets the x-axis label, and y+lm
sets the y-axis label.
fig = pygmt.Figure()
fig.grdimage(grid=grid, projection="R12c", cmap="geo")
fig.colorbar(frame=["a2500", "x+lElevation", "y+lm"])
fig.show()
Out:
<IPython.core.display.Image object>
Create a region map
In addition to providing global data, the region
argument for
pygmt.datasets.load_earth_relief
can be used to provide data for a
specific area. The region
argument is required for resolutions at 5 arc
minutes or higher, and accepts a list (as in the example below) or a string.
The geographic ranges are passed as xmin/xmax/ymin/ymax.
The example below uses data with a 10 arc minute resolution, and plots it on
a 15 centimeter figure with a Mercator projection and a CPT set to geo.
frame="a"
is used to add a frame to the figure.
grid = pygmt.datasets.load_earth_relief(resolution="10m", region=[-14, 30, 35, 60])
fig = pygmt.Figure()
fig.grdimage(grid=grid, projection="M15c", frame="a", cmap="geo")
fig.colorbar(frame=["a1000", "x+lElevation", "y+lm"])
fig.show()
Out:
<IPython.core.display.Image object>
Total running time of the script: ( 0 minutes 6.579 seconds)