I am looking for sample data set, preferably for the US. Any map scale is okay, 1:5M 1.2M etc. I need the data to test my reader.
Back when GTRI did Falconview as open source, you could download six ECRG frames for around Altanta from falconview.org. The GDAL tests use(d) that as the source.That is no longer available, but you may be able to find it on an archive somewhere (I tried wayback machine, that machine is down right now). The file name was ECRG_Sample.zip
As it turns out, we use those files for a NITF reader, and the files are checked into github at https://github.com/codice/imaging-nitf/tree/master/shared-test-resources/src/main/resources/ECRG
There is likely additional data available if you have US DoD type sponsor that can get stuff out of JITC or NGA. I'm not aware of other test data that is public / redistributable, but would always be happy for pointers.