Spline with constant -Z coordinates related to the ground level

Hi Guys,
So I want to dig a trench on the map but have no clu how to do it correctly. The bottom of the trench has to be on the same distance from the ground level so the head of the actor will be on more or less the same position above the ground. The problem is in heightmap and I cannot apply the same -Z coordinate to all Control points. Is there a way to dig the trench properly?

I don’t think so within unreal.

What you can do is take the image (heightmap) out to just about any GIS software, design a feature and have it automatically change the pixels of the map around it.

In the end you are still usually dealing with 1px per meter. So you may actually be better off making a spline tranch mesh, distributing it around, and making a hole in the landscape like we do for caves

You will 100% have problems doing that too.
Your trench has to be at least a meter, and it needs edges that go for at least 2m which you can sculpt the landscape flat against.
If you make any turn that transecs the quads the landscape uses. You will have many issues when it is painted transparent.

I guess my only option within the Editor is to move Control points one by one. That’s bad. But still thank you