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pythonscatter-plotcontour

how to create multiple contours on a scatter plot in python

I have a dataframe in which I have 3 columns each representing latitude, longitude and elevation of the point. enter image description here

I would like to create a bathymetric map of the seabed. With the code below I obtain the following map:

Df2D = pd.read_csv(r'C:\Users\Thomas\Desktop\Df.csv', header = 0, delimiter=';')

Y = Df2D['lat'].values
X = Df2D['lon'].values
Z = Df2D['elevation'].values

plt.scatter(X,Y, c=Z)
plt.colorbar()
plt.show()

enter image description here

Now, however, I would like to add contours to precise values (e.g., 0m, -10m,-50m,...) to have a more detailed map of the seabed. I tried with plt.tricontour but the result is not so good, also because it shows only one contour :

plt.tricontour(X, Y, Z, 0, linewidths=0.5, colors='k')
plt.tricontourf(X, Y, Z, 0)

enter image description here

Any ideas to increase the final result?

Solution

  • First, I'm not sure if tricontour is what you're after or just contour. You didn't talk about triangulation in your post.

    But either way, after specifying X, Y, Z, in both these functions the next arg is called levels. If you pass an integer n here (in your case, 0), the contour plot will have at most n+1 levels. If instead you pass an array, it will use the values of the array as levels.

    Long story short, replace 0 with [0, -10, -50, -100] to get contour lines at exactly those levels.