Mapping the fav dive site.

[Torgo]

SO im spending a little to much time at one site (maybe a little unhealthy) not even on scuba ( what a shock). Ok this site is close to home and is a marine sanctuary. Its fairly shallow 5m or about 16' at high tide. So the snorkle option is far more effective plus we've been getting quite a good time out there usualy 1:30 plus.

Ok so I want to start mapping the sight for future referance and to see which parts are left to explore.
I have quite a few mud maps and the such but that's where i fall short. I need an efective way (cost effective) to map the reef and rocks with a good degree of accuracy.
We know where we are under water but trying to put it in to refferance with the shore line is a different story.

 

[herman]

Here is a method several of us used on a DM mapping project. We took plastic soda bottles, numbered them and attached string to them. At points of interest we deployed one by holding it over the exhaust of our regs, adding a little air and placing it's cap on. Once we deployed the floats, we used used a kayak, a compass and a laser range finder to plot the direction and distance between each location. You could also use a GPS to plot the spots on a map.
We also took a bright red cooler and used it as a float. One diver towed it around while the other sat on the surface at a starting point watching the float. When the diver found a spot of interest to plot, he would tug on the road to make the float bounce on the surface and wait a minute or so for the surface diver to make readings. The diver would note what the point of interest was on a slate and the diver on the surface would note the direction and distance from the starting point. After the dives we would combine the 2 data bits together. We also recorded depth reading at each point of interest.
We came up with some really good maps this way.

 

[Charlie99]

If it's a shallow site suitable for snorkeling, put a GPS in a drybag that is clear so that you can still read it and punch buttons. Then just snorkel around punching in waypoints and jotting down notes in a waterproof notebook.


Another approach that works for well defined reefs is to swim around its perimeter and approximate its shape with a polygon made up of a series of legs. Each leg has a bearing from your compass and a length in "kick cycles". After that, you can then go back and start filling in depths and reef contour lines.

Here's a example of the start of a map of one of the popular reefs in S. Maui.