American cyclist Kristin Armstrong had a high-tech weapon as she trained for her push towards a gold medal in the women's Olympic time-trial - she used GPS to recreate the tough route at home.

Armstrong, a favourite to win the women's time-trial event next week, said when she was in Beijing for a test event last year she captured the route on a global positioning system.

She then laid it out on Google maps and plotted a course in Boise, Idaho that was as similar as possible to the hilly, difficult 24-km circuit between two sections of the Great Wall of China.

"I overlayed it and I'm thinking how similar is it? I'm hoping ... I'm going with it. And I come back today and rode the course today and I'm thinking - yeah, this is the grade, this is the pitch," she said yesterday after a training ride.

Armstrong hopes her familiarity with the route - even via long distance - will help as she races in the 127-km road race on Sunday and more importantly in the 24-km individual time-trial on Wednesday.

Armstrong said the course suits her well, because she loves to climb.

The American said she hopes the road race - which she does not expect to win but hopes to help propel one of her teammates to the podium - will serve to loosen her up for the time-trial.

And with luck, she said as a thick haze blanketed the area, the sun might come out by then and she'll have a clear sky as she passes around the Great Wall.

Olympic road cycling events begin tomorrow with the men's road race and end with the time-trials on Wednesday.