Hi Florian,
You can consider using a heat map chart in combination with 2D range bar (that you can use to create the labeled sections). For an example check out the following:
All Examples \ Chart Gallery \ Heat Map
All Examples \ Chart Gallery \ 2D Range Series
This is the case your surface data does not require triangulation - if it does you can still use the range series to create the rectangular sections with the labels, however you need to assign a y value which is greater than the maximum surface value (so that the surface appears below the ranges. In order to achieve interactivity on them you can assign a highly transparent white fill (say with alpha 1) so that the control still thinks the range is filled. Then you can use the HitTest method to obtain the clicked range index.
Hope this helps - let us know if you meet any problems or have any questions.
Best Regards,
Nevron Support Team