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gmt select -Fpolygon.ll hh400.ll > hh400_land.ll
eg) gmt select -F/nesi/projects/nesi00213/PlottingData/Paths/lds-nz-coastlines-and-islands/150k.gmt non-uniform-100m.ll > non-uniform-land.ll
Option 2: using gmt spatial
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gmt select -Fpolygon.ll hh400.ll > hh400_land.ll
eg) gmt select -F/nesi/projects/nesi00213/PlottingData/Paths/lds-nz-coastlines-and-islands/150k.gmt non-uniform-100m.ll > non-uniform-land.ll
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