Quick and dirty geographic longitude offset for GIS

Convert GIS data with Lat/Lon (EPSG:4326/WGS84) coordinates with longitude in the range 0-360 to -360-0 to cover -180-180 in a GIS envrionments map with this quick and dirty custom proj-style projection string.

The custom projection definition is +proj=longlat +ellps=WGS84 +towgs84=0,0,0,0,0,0,0 +pm=-360 +no_defs

This can be used as follows,

1. load a spatial dataset with Lons defined in the 0-360 range,
2. duplicate or load another layer with the same dataset,
3. set layer in 1. CRS to WGS84 or EPSG4326,
4. and set layer in 2. to a custom CRS using the projection definition above.

This process results in the dataset covering the -360 to 360 Longitude range (and implcitly -180 to 180 as well) between the two layers which can be used in a variety of different project coordinate reference systems or projections. Switching +pm=-360 to +pm=+360 will go the opposite way from (-180-180) Lons to (0-360) if necessary, because that parameter sets or modifies the default Prime Meridian Longitude in degrees-East.