iPad 3G and iPhone 4 use the Broadcom BCM4750 receiver: http://www.broadcom.com/products/GPS/GPS-Silicon-Solutions/BCM4750 http://www.broadcom.com/products/GPS/

iPad 3G and iPhone 4 use the Broadcom BCM4750 receiver: http://www.broadcom.com/products/GPS/GPS-Silicon-Solutions/BCM4750 http://www.broadcom.com/products/GPS/GPS-Silicon-Solutions/B... "High-sensitivity, -157dBm assisted acquisition sensitivity (with coarse time assistance) and -162dBm tracking sensitivity, enabling indoor and deep urban operation" You can compare this with an usual SIRF Star III based GPS receiver (Leadtek 9101x), which is not assisted: http://www.leadtek.com/eng/gps/overview.asp?lineid=8&pronameid=310&check=f http://www.leadtek.com/eng/gps/overview.asp?lineid=8&pro... With a sensitivity of -159dB and a cold start time of 35s (worst case scenario). I think that, on open water, with a good sky visibility, the GPS included in the iPad 3G and the iPhone 4 should be more than adequate for this kind of usage.