Nice find, @Wencu90 ! 
Wonder what this is… it looks like Elevation map grid (Bing data) shining through the grass. strange that NVidia can solve it, normalliy you get this when Bing is updated, ground goes up… and scenery is not bound to ground level… but in this case it is grass ! The sim must show that over the DEM-map. Maybe this has something to do with height calculation precision ? NVidia sets it ? This is a solution to remember ! This issue has come up quite a few times…