How to handle a topogrophy with incorrect coastlines?

Hello Everybody,

For a project, I need to plot the topography of corsica (42.204107, 9.129181). Both sources of topography data I know (SRTM and Noaa.gov) support only data where the coastline of the isle is not correct. At low elevations the land is part of the ocean.

To correct this I plottet the additional coast line data wich I also downloaded from SRTM as a simple vector with the function fillseg.m. The topography I plottet with contourf. My idea was to plot the correct coastline and set the topography above. So when you have a simple 2D plot it should look correctly.

The problem I have at this point is that the topography always is set to the background and even with changing the plot order or using additional function like uistack I had no chance to get the coastline to the background or the topography in the foreground. The second approach I had, was to use an "inverse" function to fillseg, which das not fill the inner part of the coastline, so I can make a clean cut of the topography, even when displaying order of both elements could not be changed. Does anybody know a function like this?

Has anybody an idea to solve this problem, maybe someone has a completly different approach how to handle incorrect coastlines in topography data. For anybody helping me, great thanks.

Kind regards and thanks for helping, Thom-