The victim fell asleep and about 2.30am was woken by Yeatman touching her genitalia. She pretended to be asleep in the hope he would stop but the touching continued to her breast.
The woman eventually got up the courage to get out of bed once she heard the noise of a zip.
Without her knowledge, Yeatman also took a photo of the victim's legs and bottom only clad in underwear.
After leaving, Yeatman texted his friend saying "I think I f***** royally ... I think I got a bit hanzy and upset [victim] ... "
In July, Yeatman accepted a sentence indication that he had earlier rejected from Judge Glen Marshall, on charges of unlawful sexual connection and making an intimate recording.
Yeatman's lawyer Tom Sutcliffe said apart from a drink-driving conviction it was the first time his client had appeared in court.
Sutcliffe said his client was bereft of support initially because he was too embarrassed to tell his family what he had done.
"He has, subsequent to being in a position where he needed to tell the family, got support around him and common sense came into play and that's when counsel received instructions ...that he wished to plead guilty."
Sutcliffe said his client was a "young man completely petrified about the idea of going to prison and that is a reality that he had to face".
"More particularly also that this will be a black mark against his name and an obstacle in many ways of obtaining future employment and forging a career for himself. All of those are matters that he has struggled with in a completely out-of-character decision to do what he did that night and he completely regrets it and has come to accept that he is responsible for his own actions."
The time he had already spent in custody had been a "salutary" experience, Sutcliffe said.
He also had many letters of support from "family and others" about his offending. Yeatman had also offered an emotional harm payment of $3000.
Crown prosecutor Duncan McWilliam said the effect on the victim was "profound".
"The psychological impact on the victim, the sense of loss that she had felt, the effect on her sleep patterns, and that had the effect in terms of a loss of income from her job and it also affected her study."
In her statement she wrote "all I can ask is that he realise how hurt I am and how empty and alone and broken I feel because of something he did".
Judge Marshall got down to the home detention range - within 24 months - of 20 months' prison but said the offending was too serious to be dealt with by way of home detention.