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I have a geotiff raster of Indonesian landsystems which I need to clip to the Papuan provinces in New Guinea. Unfortunately, I can't use a rectangular extent (as this would include some of the nearby islands) and I can't find a boundary shapefile that's accurate enough (some tiny islands belonging to Papua get left out).

I'd like to draw a polygon round the area - just drawing the lines through the sea between Papua and the other islands, setting the vertices etc - so I can clip out the islands I don't need. But does QGIS even allow me to do this? The digitizing toolbar only has certain shapes and even then, you have to be editing an already existing vector layer. So you can't draw a new polygon...?

I'm new to GIS and this question may sound obtuse. Apologies if so - but really, what's the use of a GIS app if you can't draw your own shapes? Is there any other app out there I could use in Windows?

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    You need to create a new polygon layer under layer -> create layer, which you then may edit. – Erik Apr 30 at 7:56
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Create a new layer and add a new polygon feature by clicking the Add Polygon Feature icon, see the documentation. Than manually draw the polygon you like.

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  • It worked! Having said that, I must admit I failed to mask the raster with the new layer until I added geometry to the new layer with Vector / Geometry Tools / Add geometry Attributes. – Michael Smith Apr 30 at 9:02

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