MELISSA MOLE knows exactly where she is on the planet.
The quad bike she uses to survey NSW beaches has sophisticated GPS technology that can communicate with more than 10 satellites to pinpoint her position to within two centimetres - less than the depth of a footprint in the sand.
As Ms Mole, a PhD student at the University of NSW, rode up and down Narrabeen-Collaroy beach this week, mapping its fine structure at ground level, other researchers flew overhead, scanning the 3.6 kilometre stretch of sand from the sky.
The research is part of a new project to forecast how changes in wave patterns and rising sea levels will affect beach erosion around the world. ''The better we understand how a beach behaves now, the better chance we have of predicting how it is going to behave in the future,'' Ms Mole said.
Ten NSW beaches , from Lennox Head in the north to Shoalhaven Heads in the south, will be monitored for the next three years.
All beaches will be photographed throughout the day, and surveyed each month by quad bike. Specially equipped jet skis and boats will study the ocean floor to a depth of 20 metres.
At Narrabeen-Collaroy and Wamberal-Terrigal beaches, buoys will measure the height and power of waves.
The plane will use optical remote-sensing technology called LIDAR to scan these beaches monthly at low tide.
The team leader, Ian Turner, said the plane would also be sent up during rough weather. ''It will measure the beach as it is changing during a storm.''
The information will be used to develop a computer model, the ''first global tool'' that can forecast erosion at any sandy beach around the world as the climate changes, Professor Turner of the UNSW Water Research Laboratory, said.
Narrabeen-Collaroy is rare in having been monitored by scientists since 1976, revealing little overall change but large variability, as sand is swept away in storms and then slowly returns.
''We've seen the width change by as much as 80 metres,'' Professor Turner said.
Sea level rise - about nine centimetres in the past 30 years - has had little effect as yet, he said. In future, however, larger storms, approaching the coast from different directions, are predicted to have a bigger impact on the coast.
The Australian Research Council project also involves Macquarie University, The University of Plymouth, the NSW Office of Environment and Heritage, CoastalCOMS and Warringah and Gosford city councils.