Add an example of the use of pygmt.grdgradient

[yohaimagen]

I noticed that there are no examples of the usage of pygmt.grdgradient and a function without examples is much harder to utiles by new users.

I suggest adding an example of making an hillshade map using pygmt.grdgradient as so:

grid = pygmt.datasets.load_earth_relief(resolution="01m", region=[-14, 30, 35, 60])
dgrid = pygmt.grdgradient(grid=grid, azimuth='90/10')
fig = pygmt.Figure()
pygmt.makecpt(cmap='gray', series=[-1.5, 1, 0.01])
fig.grdimage(grid=dgrid, projection="M5c", frame="a", cmap=True)
fig.colorbar(frame=["a1000", "x+lElevation", "y+lm"])
fig.show()

this example can be an extension to the Earth relief tutorial or as a separate gallery example.

Are you willing to help implement and maintain this feature? Yes

[weiji14]

Cool, this is a good idea! My only suggestion would be to either 1) use a smaller region rather than the whole of Europe if you want to use a high resolution map or 2) keep things to a low resolution (e.g. 10 arc minutes). Mainly because grdgradient can be a processing intensive task that can take some time to run.

[seisman]

I suggest adding an example of making an hillshade map using pygmt.grdgradient as so:

grid = pygmt.datasets.load_earth_relief(resolution="01m", region=[-14, 30, 35, 60])
dgrid = pygmt.grdgradient(grid=grid, azimuth='90/10')
fig = pygmt.Figure()
pygmt.makecpt(cmap='gray', series=[-1.5, 1, 0.01])
fig.grdimage(grid=dgrid, projection="M5c", frame="a", cmap=True)
fig.colorbar(frame=["a1000", "x+lElevation", "y+lm"])
fig.show()

If I understand "hillshade" correctly, this script does not produce a hillshade map. Usually, we need to pass the DEM grid to the grid parameter and a gradient/intensity grid to the shading parameter.

this example can be an extension to the Earth relief tutorial or as a separate gallery example.

I agree we should extend the tutorial to show how to add shading to the earth relief map. I think the easiest way is simply adding shading=True to the grdimage call.

[yohaimagen]

I can do both, extend the tutorial with an example that uses shading=True which gives nice output and does not overpopulate the tutorial. from this section of the tutorial, we could refer to a gallery example with more specific use of grdgradient(shading=True use grdgradient to produce intensity grid file)