Victoria McClure, 38, 'drove blind' as she attempted to use the zoom function on the device while driving down a 60mph road, the court was told.
There was no evidence that she braked before crashing into 46-year-old cyclist Anthony Hilson near Twyford, Berkshire, on a long straight section of road, the jury heard.
Mr Hilson, who was out for an early Sunday morning ride, died after suffering 'devastating and unsurvivable' injuries.
McClure, who was on the way to a baby shower, has admitted causing death by careless driving but denies the more serious offence of causing death by dangerous driving.
Prosecutor Matthew Walsh said motorists on the A4 Bath Road where the married father was killed would have typically had about 500m of clear visibility.
'Assuming for a moment she's travelling at the speed limit of 60mph, it takes about 18 seconds to cover the distance - that's the length of time she would have had the cyclist in her view,' he said.
'In other words, she had a window of about 18 seconds - maybe more, of course, if she was going slower - approaching the cyclist in order to see him.
'But she didn't. Did she try and take any avoiding action, braking or steering?
'Well, from the witnesses that were in the general area, nobody heard the sound of braking or horns or anything of that nature.
'There weren't any skidmarks on the road to suggest emergency braking or any evasive action.'
McClure was at the wheel of her Honda Accord when she crashed into the cyclist on September 16 last year.
The jury was told steering lightly to the right would have been enough to pass Mr Hilson as he travelled in the same direction on his Specialized road bike.
McClure said at the roadside and in a police interview that she had taken her eyes off the road to use her sat-nav, the court heard.
She allegedly told police officers she had been zooming in on her sat-nav and added: 'I looked up and it was too late. In the blink of an eye I just hit him. I didn't think I was going that fast.'
There was no suggestion McClure had been speeding, Mr Walsh added.
Crash scene: The accident happened on a long straight section of the A4 Bath Road (pictured) near Twyford, Berkshire, the court was told
She replied: 'I think the cyclist was there all the time. I think I just didn't see him.'
McClure had admitted causing death by careless driving, Mr Walsh told jurors.
'In other words, she accepts she caused Mr Hilson's death that day, she says by careless driving.
'The prosecution say it goes beyond that, it was more than careless driving - it was dangerous driving.
Accused: McClure outside court where she is standing trial accused of causing death by dangerous driving. She has already admitted the less serious charge of causing death by careless driving
A post-mortem examination revealed that Mr Hilson had died of severe head and chest injuries.
Gill Cox, an editorial designer, told the court she and her husband Pete were on the way to church when she spotted what she initially thought was 'a pile of clothes' in the road.
While her husband, an ex-police officer, went to try and help Mr Hilson, Mrs Cox said she went to McClure's side.
She said: 'She was clearly very stunned and said "What have I done? I have probably wrecked some lives. If I have, how am I going to live with this?"'
Off-duty ambulance nurse Matthew Bailey was passing the scene at the time and stopped to offer assistance.
McClure, of Charvil, Reading, denies a single count of causing death by dangerous driving but has admitted causing death by careless driving.