Note
Go to the end 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
function. 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 shown at https://www.generic-mapping-tools.org/remote-datasets/earth-relief.html.
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()
![earth relief](../../_images/sphx_glr_earth_relief_001.png)
pygmt.Figure.grdimage
can take the optional parameter projection
for the map. In the example below, projection
is set to "R12c"
for
a 12-centimeters-wide figure with a Winkel Tripel projection. For a list
of available projections, see https://docs.generic-mapping-tools.org/6.5/reference/map-projections.html.
fig = pygmt.Figure()
fig.grdimage(grid=grid, projection="R12c")
fig.show()
![earth relief](../../_images/sphx_glr_earth_relief_002.png)
Set a color map
pygmt.Figure.grdimage
takes the cmap
parameter 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/6.5/reference/cpts.html.
Using the geo CPT:
fig = pygmt.Figure()
fig.grdimage(grid=grid, projection="R12c", cmap="geo")
fig.show()
![earth relief](../../_images/sphx_glr_earth_relief_003.png)
Using the relief CPT:
fig = pygmt.Figure()
fig.grdimage(grid=grid, projection="R12c", cmap="relief")
fig.show()
![earth relief](../../_images/sphx_glr_earth_relief_004.png)
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
parameter for pygmt.Figure.grdimage
. The frame
parameter 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()
![earth relief](../../_images/sphx_glr_earth_relief_005.png)
Create a region map
In addition to providing global data, the region
parameter for
pygmt.datasets.load_earth_relief
can be used to provide data for a
specific area. The region
parameter is required for resolutions at
5 arc-minutes or higher, and accepts a list (as in the example below) or a
string. For the later, the geographic range is passed as
“xmin/xmax/ymin/ymax”.
The example below uses data with a 10 arc-minutes resolution, and plots it on
a 15-centimeters-wide figure with a Mercator projection and a CPT set to
geo. frame="a"
is used to add a frame with annotations 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()
![earth relief](../../_images/sphx_glr_earth_relief_006.png)
Total running time of the script: (0 minutes 1.223 seconds)