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I am fairly new to QGIS and am using XYZ Tiles for OpenStreetMap and shapefile layers from GADM to see boundaries in Kenya (to start). I have an OpenStreetMap layer and gadm41_Ken_1.shp layer and the boundary lines are off from each other. I tried "Check Geometry" but rendered no changes.

Does anyone have any tips or ideas?

enter image description here

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  • That looks like a datum offset - you might want to transform the boundaries into WGS-84 to match the OSM data.
    – Toby Speight
    Commented Jul 11, 2023 at 14:00

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I don't think you can expect the data to be perfectly aligned. It depends on how and in which projection the GADM geometries have been created. Geoprocessing and projection conversions can introduce differences in accuracy and coordinate precision. Which eventually propagates to the situation you have now. A simple operation as rounding of the coordinates can transform a geometry.

Without knowing how GADM creates the geometries and what processing is applied, there is - I think - no way to know how to easily fix this.

If you want the geometries to align, why don't you use the OSM data itself? There are a lot of plugins in QGIS that make it easy to filter the data based on administrative boundaries and download it directly into QGIS.

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