Thank you for your response, and thank you for the different tips concerning visualisation. I'll improve it.
I've tried to put vmin and vmax in contourf(). It works but the values above 80% of the maximum value still remain red which makes the cartography not really clear. I think I should in black, or white, every values above 80% of the maximum value. -- https://mail.python.org/mailman/listinfo/python-list
