I think that Oruxmaps (OM) has a problem with some of the GDA2020 files (though I can not get an answer on the OM forum, or anything sensible from the NSW spatial ‘service’).
The reason I think this is that both the 2016 and the 2020 versions of the Pottsville map give the same (only slightly inaccurate) location using the Adobe Reader Geospatial Location Tool. For some reason, metadata shown by TerraGo shows that both versions use GDA94 (although the new ones are distributed as GDA2020). Probably much like Tom in QGIS, which I have not tested.
The CollarOff versions of the maps from the NSW.spatial website are in geotiff format, and AsTiffTagViewer shows that the 2020 maps specify GDA2020 in metadata. But they will not open in OM (version 7.4.28). Nor can OM open geopdf maps converted from the 2020 Pottsville geotiff using the (very slick) online converter at
https://gdal3.js.org/; though Adobe Reader opens these converted files without problem.
One workaround is to use Map tweaks > Map calibrator in OM, though it is not entirely satisfactory (probably because it uses only a single point to calibrate).
What did work well for me (after I downloaded the geotiff file from NSW.spatial to C:\temp\pottsville.tif) was to use gdal programs: first gdalwarp -t_srs EPSG:4326 C:\temp\pottsville.tif C:\temp\pottsville1.tif (to get a WGS84 re-projection - though it will still not open in OM), then gdal_translate C:\temp\pottsville1.tif C:\temp\pottsville1.pdf to get it into geopdf. This aligned perfectly under my track in OM (better than the 2016 map direct from the NSW.spatial website, which has that slight E-W error). Whew, what a run-around.
- GDA2020 geopdf re-projected to WGS84
- Screenshot_20240424_150359_OruxMaps.jpg (94.64 KiB) Viewed 2274 times
The cached wms maps align perfectly under my track, so the errors seem to be associated with OM handling of the geopdfs.
- 2016 (cached) WMS
- Screenshot_20240424_150610_OruxMaps.jpg (92.58 KiB) Viewed 2274 times
I think the take-home message is that OM (version 7.4.28) is happy with WGS84, but may be confused by at least some pdf maps in GDA94 or GDA2020 (these are not listed under OM Map tweaks > Map Datum, but at inception they were very close to WGS84).