 Underwater GPS book
Diving with GPS:
I've been using a non-commercial web site (MSN group) to promote a simple way of using GPS while diving. Just as on land, this is not intended to replace basic
navigation skills and good judgment. My goal has been to provide a simle way to gain GPS data to "mark" points of interest, while keeping an eye on the boat's anchor position. I've avoided the predictable towed antenna arrangement...I want this to be a true off-the-shelf, grab it and go method. The Magellan hand-held units continue to display data after signal is lost...this creates the opportunity to use this method. Depending on depth and conditions, several variations of the method can be used. The gps activated and placed inside a clear container. To gain data...the postively bouyant container is dropped...ascends the surface...gains signal update...and is pulled back below to
view data. To avoid the wait for signal (about 60 seconds)--the diver can leave the container on the surface...only pulling down as data is needed. This puts the diver about 5 seconds from data update at any time. My non-commercial web site has further details, and a free downloadable eBook
(pdf doc.) is available. Most divers are not in the water enough to bother with this, but the most avid--and the research community may benefit from the concept. I've been getting some good feedback from researchers (and even one treasure diver). I hope this may be helpful to you.
*Note: I'm frequently asked if the deployed container drifts to a distant locaton, rendering the "mark" innacurate. This is not a problem...the container deploys quickly...the amount of line is controlled...and what matters is where the container is pulled down (loses signal)...not where it happens to travel on the surface. | 
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