dat, which lists collections of unit names. The names given therein and their plural forms will be regarded as acceptable unit names for this standard with the following additions and deletions:</p>
<ul><li>"degrees" - deleted</li>
<li>"level", "layer", "sigma_level" - added</li>
</ul><p>The unit "degrees" creates ambiguities when attempting to differentiate longitude and latitude coordinate variables; files must use "degrees_east" for units of longitude and "degrees_north" for units of latitude or the alte