Josm and georeferenced Sentinel-2 images

Help and support
1

I want to use georeferenced Sentinel-2 imagery in JOSM because it would be useful for my mapping, and I understand that its license is compatible.

The problem is that the images don’t align correctly with the data.

In the Copernicus Data Space ecosystem, I download the selected area as an 8-bit TIFF image with a high-resolution EPSG 3857 projection.

In JOSM, I’ve ensured the projection is correctly set: Preferences > Map Projection > Method: Mercator, Code: EPSG 3857.
Then, I use “New Image Layer from File” to import the image. The displayed image is not to scale and has an offset of approximately 3 km.

Have I missed something to make it work correctly?

2

Problem solved! …My mistake.

JOSM ImportImagePlugin documentation says that a world file is required to make the plugin work, which is not provided in the Copernicus Data Space ecosystem. After I created one with QGIS the image loaded properly in JOSM.

Good to know.

3

So the issue is that it’s a plain TIFF file, not a GeoTIFF? Or that even GeoTIFF files in JOSM need a world file?

Would be also good to know.

4

Long answer…
I assume the image was a GeoTIFF file since it is what I asked for, and was able to create a world file in QGIS without georeferencing the image manually.

I first assumed JOSM could manage the GeoTIFF file directly, but since I was not able to display it correctly, I asked for help in this post.

Waiting for an answer on a topic I’m not used to, I kept digging by reading more thoroughly the plugin documentation (see the above link) where I found…

REQUIRED: the image file (Supported formats: GeoTiff, Tiff, …)
REQUIRED: a world file (<image_name>.wld… or “.tfw” for Tiffs)

Short answer, it seems that even GeoTIFF files in JOSM need a world file.

5

Sure. Thanks.

Short answer, it seems that even GeoTIFF files in JOSM need a world file.

Maybe a ticket on JOSM plugin could help. Best option: use the georeferencing info from the GeoTIFF file. Second option: refuse to load the file if the world file is missing. In that case, you still have to do the work, but at least you are informed.

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