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I have a set of DEM tiles (TIFF format) retrieved from https://cteco.uconn.edu/data/download/flight2016/index.htm which I would like to convert to 16-bit PNG format so that I can use them as heightmaps in Unreal Engine 5.

Referencing this question and this question, I downloaded QGIS3 and used the Raster → Conversion → Translate menu to attempt conversion to UInt16 with the following command:

gdal_translate -ot UInt16 -of PNG H:/Programming/Heightmaps/840630nw_x0_y0.tif H:/Programming/Heightmaps/output.png

The resulting image, however, is completely black and trying to import it into UE5 gives me a completely flat landscape so it's not just the preview unable to render. When I inspect its properties using the Windows context menu, I see that the pixel depth is 64 bits as opposed to the 16 I would expect. If I try any of the other output data types such as Byte, I get a depth of 8 bits which results in a blocky heightmap.

I don't work in the GIS space and have never done any image manipulation so talk of bands and depth goes a bit over my head. I am hoping someone can explain what might be going wrong and how I can fix it.

EDIT: Results from commands suggested by @user2856 here.

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    Works for me. Make sure you download the file labelled "DEM", not "TIFF", e.g. cteco.uconn.edu/download/DEM/2016/tiles/790755_nw.zip. The zip contains a GeoTIFF, but it's the actual elevation data, not just an image. I then ran gdal_translate -ot UInt16 -of PNG 790755_nw.tif 790755_nw.png and got a single band 16bit PNG with correct elevation values (checked in QGIS). If this is not working for you, edit your question and add the outputs of gdalinfo -stats 840630nw_x0_y0.tif and the same for the output png.
    – user2856
    Jul 16, 2021 at 0:49
  • Forgot to mention... my output png looked completely black when I accidentally opened it in the default Windows image viewer, but that because that software was designed to handle pictures, i.e 3 or 4 channel (band) RGB or RGB+Alpha 8bit per channel files. I notice Windows reports your output as 64bit, which makes me think you may have downloaded the "TIFF" image (your output png would have 4 channels, each 16bit == 64bit). If your input tif is a few mb file size (790755_nw.zip DEM is 3.7mb), you've got the elevation, if it's hundreds (790755_nw.zip TIFF is >300mb) you got the aerial imagery.
    – user2856
    Jul 16, 2021 at 2:49
  • Okay; interesting. I re-downloaded all the tiles making sure to get the DEM versions. I thought maybe that solved my problem since the first one I converted came out properly as 16-bit. However the second is still producing a 64-bit result. I also get an error in QGIS with that one: Warning 1: for band 1, nodata value has been clamped to 0, the original value being out of range. I am updating the question with the results from the console commands.
    – Matt
    Jul 16, 2021 at 4:10
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    No your output PNG is 16 bit according to the gdalinfo output, the only difference I can see is the NoData value metadata. Try adding -a_nodata None in "Additional command-line parameters" - gdal_translate -ot UInt16 -of PNG -a_nodata None 840625_nw.tif 840625_nw.png
    – user2856
    Jul 16, 2021 at 4:58
  • Hmm it got rid of the error but Windows still shows that file as having 64-bit depth although I see from gdalinfo that it is indeed UInt16. I get the same flat plane when importing either result into UE5 though so it seems even the one that's "working" isn't actually working.
    – Matt
    Jul 16, 2021 at 5:15

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