I downloaded ESRI ASCII file for bathymetry from GEBCO. Now I loaded the file as raster, then I clip the raster file according to my vector images (Image 1), then I did symbology, where I did single band pseudo-color. but the problem is that the min-max value are not the value of water depth (Image 2). How do I calculate it from the ASCII file? I am using QGIS 3.18

enter image description here

enter image description here

  • 1
    Coordinates at bottom of screen show 24.7371,118.2500, which would be Xiang'An, Xiamen, Fujian, China, which is not close to water. Please post your ASCII file or the bounding box you used in GEBCO.
    – Pointdump
    Commented Mar 14, 2022 at 7:13
  • -126 is 126m below sea level, 871 is 871m above sea level.\
    – user2856
    Commented Mar 14, 2022 at 8:10

1 Answer 1


The range of your original bathymetry files is between 1.537 and -201, as per your screenshot "Image 1", so the clipped area should be within that bracket.

I think something unwanted has happened in the clipping process.

To make sure, double click on the clipped file and check its actual value range under the "Information" tab:

enter image description here

  • Sir, that is the pre-cliped image, but I cliped it according to my vector file after that the ranges come between 1.537 and -201. if you look at vector file you can see the river line and ocean, now I want to calculate the depth only where are the water including the river.
    – Kazi
    Commented Mar 14, 2022 at 13:31

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