degree celcius unit conflict with udunits2

[srstsavage]

In ucar.units.SI, the symbol for degrees celcius is specified as "Cel":

https://github.com/Unidata/thredds/blob/master/udunits/src/main/java/ucar/units/SI.java#L520

However, in the udunits2 xml files, the symbol is specified as "°C":

http:https://www.unidata.ucar.edu/software/udunits/udunits-2/udunits2-derived.xml

In addition, there is no alias defined in SI for "°C", so trying to parse "°C" with a ucar.units.StandardUnitFormat fails.

[semmerson]

Shane,

You're right. The C-based UDUNITS-2 package is more capable than the Java-based ucar.units package.

The ucar.units package needs to be enhanced. Unfortunately, I don't have the time to do that right now.

As a workaround, I've always recommended using completely spelled-out unit names rather than symbols. Yes, it's more verbose -- but it does lead to fewer problems and less confusion.