Geoscience Reference
In-Depth Information
Fig. 7.9
Contour plot of a data set gridded using a biharmonic spline interpolation. No control
points are available in the upper let corner. h e spline interpolation then extrapolates beyond
the area with control points using the gradients at the map edges, resulting in unrealistic
z
estimates at the grid points.
text(data(:,1)+1,data(:,2),labels)
hold off
Alternatively, we can eliminate a rectangular area with no data.
ZID = ZI;
ZID(131:201,1:71) = NaN;
contourf(XI,YI,ZID,v)
caxis([-40 40])
colorbar
hold on
plot(data(:,1),data(:,2),'ko')
text(data(:,1)+1,data(:,2),labels)
hold off
In some examples the area with no control points is simply concealed by
placing a legend over this part of the map.
Other interpolation methods available with
griddata
are the cubic (
cubic
),
natural neighbor (
natural
), and nearest neighbor (
nearest
) interpolation
methods. h e
cubic
option interpolates the data in two dimensions using