Exporting separately ground and the sea from QGIS as TIFF files

Question

I am very bad at QGIS, but I really need to have TIFF of the area on the picture, to export it later to Unreal Engine. The problem is the sea. Unreal takes it as a part of the ground. It doesn’t recognize the water. How can I export height map of the ground separately from the sea?

dem geotiff tiff qgis

Babel · Answer

Get a polygon layer of the water surface, for example from OpenStreetMaps (OSM). See here how to download: https://gis.stackexchange.com/a/368774/88814. Another option is to use the QuickOSM plugin. You can use the OpenStreetMap tags natural=water (red on the screenshot) and natural=bay (blue).

You will get many very small water features, so probably you want to keep only a few and delete all that are smaller than a certain area. When extracting from OSM, keep the polygon layer only, delete line- and point layers.
Screenshot: using QuickOSM to extract features tagged natural=bay from OSM:

Than use the tool Clip raster by mask layer from the Menu Raster / Extraction (alternative: SAGA tool  Clip raster with polygon).

Exporting separately ground and the sea from QGIS as TIFF files

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