Digitation is spelled with a "g" in the middle, even though it sounds like it should be spelled with a "j". This is because the "g" in this word is pronounced like a "j", as in the word "magic". The IPA phonetic transcription for the word is /ˌdɪdʒɪˈteɪʃən/. The "d" sound at the beginning is followed by the "i" sound, as in "sit". The "g" sound is pronounced like a "j", and the rest of the word is pronounced as it is spelled.
A division into finger-like processes.
Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874.