Google Trekker lets you walk through our local National Parks, from the comfort of your laptop. See how it works in this video produced by ABC Open producer Sean O'Brien. Sean joined ranger Dr. Rowena Morris on a recent walk along the Maddens Falls track in the Dharawal National Park. From the Google Trekker backpack, 15 cameras shoot a 360 degree panoramic image, all the while connected via GPS to a satellite. When it's all stitched together, it's as if you're walking with Rowena. The Maddens F