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I want to create application map for agriculture based on NDVI map. I have theoretical way how to do it.

My raster has two values (1 - red, 0 - green), the raster is quite big (100 hectares with 6 mm pixel size).

I need to create polygons which contains all the red pixels (as on the picture) - ideally with some buffer. Result should be shapefile (so Raster to Polygon) with maximum number of 50 000 polygons, so I need to generalize polygons and merge to achieve smaller amount and shorter computation time.

Polygonize often use big amount of time. I also tried make just worse resolution, it works quite well, BUT I need that the new pixel (for example 1 m resolution) need to be red even if only one former pixel was red. Any red place can't disappear. Best would be if I don't have to polygonize it first because of waste of time, but generalize and merge it first and then polygonize.

In QGIS or ArcGIS.

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  • Please ask only one question per Question ("QGIS or ArcGIS" is two questions) – Vince Mar 31 at 13:34
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Try resampling using Maximum method to assign new pixels 1 even if a majority of the values are 0. For example using Warp in QGIS. Then vectorize.

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    Thanks a lot, that works! – daky Mar 31 at 12:41
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I've found some solution. As @BERA wrote, in QGIS the function Wrap does the work. In ArcMap very similar is function Aggregate. The resolution is decreased and with the use of Maximum type of agregation/wraping, no "1" value is omitted. Then the vectorization is really fast.

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