In my experience, there are no standards. Every EGD firm I've worked with and/or worked for has had its own standard nomenclature, abbreviations,
sign type hierarchy, etc. The same goes for every
sign company I've worked with and/or for. It's gotten really confusing at times when the EGD firm & the
sign fabricator both wanted to use their standards when preparing submittals and shop drawings.. I don't think it would be possible to have a set of standard abbreviations tho because there are so many different
sign types and, because every firm/fabricator has its own nomenclature and terminology, there so many different names for each of those
sign types. Are you trying to decipher someone else's plans or are you designing a wayfinding program for a client?