import topotoolbox
import matplotlib.pyplot as plt
dem = topotoolbox.load_dem('bigtujunga')
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
_= dem.plot_surface(ax=ax)
ax.set_aspect('equal')
_= ax.set_zticks([0,np.nanmax(dem)])
plt.show()