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I've manually created mosaics of some island chains using the SRTMGL1 v3 data, for example the Hawaiian Islands. From a mosaic, I want to create a set of separate rasters for each of the islands. (I'd be happy to also exclude 'small' islands.)

raster mosaic of hawaiian islands SRTM

I want to be able to automate it as much as possible, as I'll eventually want to do it for a series of island groups. Using PyQGIS seems like the best option, but I am a little stuck with how to begin.

I've tried by polygonising the raster to create masks, but I need to manually select polygons from the result, and manually remove boundary polygons.

hawaiian islands polygonised

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  • For questions that involve code we ask that you show us where you are stuck with your own code by including a code snippet in your question. There is an edit button beneath your question which will enable you to do that and a {} button that enables you to format any highlighted code nicely.
    – PolyGeo
    Jan 8, 2020 at 8:51
  • @PolyGeo I didn't involve any code yet as I wanted some help with the design of the workflow. There is no code - as I stated I am not sure where to begin. Can you please reopen the question? Or do you want me to reword it? Jan 15, 2020 at 4:05
  • As soon as a question strays too far from "this is a particular thing that what I want to do, this is precisely what I've tried and this is where I'm stuck" it starts to be hard to recognize as focused Q&A. For coding questions (and your PyQGIS mention in the body and PyQGIS being amongst the tags indicate that you are asking a coding question) we ask that you include a coding attempt rather than just asking for coding help. If you are not yet at a coding stage then perhaps you can start testing a QGIS Modeler workflow and ask about where you are stuck with that.
    – PolyGeo
    Jan 15, 2020 at 4:12

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