Blank orthophoto export

Normally I can view the exported ortho TIFF files in Gimp, but my just complete orthophoto (21 hours, 4965 X 20MP images, 5 square km area) is blank white. It looks ok in WebODM (apart from the annoying vertical white lines that prevent nice screen grabs), and the DSM and 3D images also look good.

In GIMP the image seems to be made up of a single 159MB image, whereas normally I see about 8 images of various sizes/resolutions to select from. Importing as layer or image makes no difference.

Any suggestions as to what might be the problem?
blank-image

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GeoTIFFs are Raster Data, not images. Similar, but different enough to cause headaches like this at times.

GIMP is likely choking on something in the file (BigTIFF?). Paint.NET has pretty strong GeoTIFF support, but really, it should be opened by a Geospatial program.

Does it display normally in QGIS, for instance?

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I have QGIS installed, but am not at all familiar with it. Dragging the image into it gives this, which looks nothing like it should.QGIS-blank-image

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Nah, looks right. You have a single-band image with the default palette applied.

You can change the layer symbology to use another color ramp to mimic the appearance you see in WebODM. Or use another you may like better!

Incidentally, this is a great example of what I said above. This is data in a grid. The data values are roughly 420ish-570ish per pixel in this case. WebODM applies a color ramp to aide visual analysis. Same for QGIS. However, it doesn’t really look like anything on its own, and GIMP showed you data VS nodata, basically, since that was all it could display without a ramp/paletted interpretation.

Colors in most normal 8bit depth images are in the range of 0-255 (integer) for each band of Red, Green, and Blue, the composition of which gives you an RGB color value per pixel. So you can see why GIMP didn’t show you much, since it had a single band of crazy non-normal values. It really should stretch/palette to grayscale like QGIS does.

So, you can symbolize it in QGIS, or in WebODM you can export the symbolized image as a rendered GeoTiff, which is a great way to “burn in” your visualization to ensure others see it the exact same way. Note that this changes (or ruins, if you’re not being generous) the data. No longer suitable for numerical analysis.

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I’m not sure I understand some of that :wink: but if I import from all.zip, then I see the image properly, as I have done for all my other exports :slight_smile: This time however, there was no choice of any of the 8 or so different resolution versions

part of it at 12.5% magnification:

Not-blank-image

The difference is that the first blank one comes from exporting the geotiff, but the good image comes from the geotiff included in all.zip.

The good news is that effective 10cm resolution orthophotos (due to scaling the image 0.25X linear) can be produced from ~5000 images in WebODM in less than a day :slight_smile:
If I wanted full ~2cm resolution it might take a week on my computer though!

Yep, it seems like you had exported the DSM, DEM, or DTM as GeoTIFF. They will be single-band grayscale images as I described.

The Orthophoto is what is a colorized photograph of the area.

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Yes, it seems I exported the wrong item!

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