[Qgis-user] how to properly reference longitude values in different datasets

[Lee Eddington]

I’m pretty new to QGIS and am trying to figure out how to modify longitude values of layers.  I was able to add a raster layer in GRIB2 format (NCEP global meteorological data).  The longitude values range from 0 to 360 degrees.  I’m able to view and do calculations on the data with no problem.  I also added shaded relief and coastline data from Natural Earth.  This data has longitude values from -180 to 180 degrees.  So from -180 to 0 degrees I only see the Natural Earth data, from 0 to 180 degrees I see both datasets and from 180 to 360 degrees I only see the GRIB2 data.  I want both datasets to be referenced the same with regards to longitude (-180 to 180, 0 to 360 or whatever).  It seems like this should be a fairly easy problem to fix by either adding 180 degrees to longitudes from the Natural Earth data or subtracting 180 from the GRIB2 longitudes, but I can’t figure out how to do it.

I’m using QGIS version 3.4.1-Madeira.  The CRS I’m working in is what QGIS put the GRIB2 data into when I added it:   * Generated CRS (+proj=longlat +a=6371229 +b=6371229 +no_defs)

Thanks,
Lee