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I need to know the extension of the area of a lagoon according to depth classes. I started from a point shapefile containing depth values and used the interpolation plugin and I obtained a raster file. I used the contour function, but I can't convert lines to polygons. I tried the polygonize tool on the raster file, but this function only makes intervals between the polygon of 1,0, whereas I need intervals of 0,5 m.

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  • Please provide your settings for the polygonize tool.
    – Erik
    Apr 26, 2021 at 11:55
  • I use the tool: Raster > Conversion > Polygonize
    – Monia
    Apr 26, 2021 at 13:45

1 Answer 1

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  1. Reclassify your data using the Toolbox Reclassify by table

  2. Run a raster layer unique values report

Here's some bathymetry

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Classified using ranges - data outside of ranges are ignored. Assign a unique value for each range.

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The report on the range - third column has the area in metres.

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Confirm that summing the areas gives the same total as the area of the original (unclassified) bathymetry.

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  • thank you very much!
    – Monia
    Apr 27, 2021 at 8:41

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