DM Mapping Project

[oceancrest67]

I am a current DM candidate that has been diving for the past ten years...(yes, I decided to go for my DM after some years of diving). I only have a few items left to complete on my DM...one of them being my mapping project.

Now the mapping project is described in the DM Padi handbook as a routine cross sectional, fin kick, depth marking, grid pattern...to and fro over the terrain...with a dive buddy...of course there are other ways to map a section of underwater terrain. My point here is that the book gives a rather cursory overlook that is not all that helpful.

I spoke with several instructors and they all give me differing answers on the 'best way' to accomplish mapping some underwater terrain (a quarry in this case).

My current instructor wants contour lines indicating depth of every 5 feet...contour of terrain etc. His method requires marked balloons, a team of divers, and a survey compass to triangulate to each balloon on the surface.

My question: I think I am almost fulfilling a navigation certification on top of my DM mapping project. Has anybody else worked on their DM mapping in this format? Anybody have a good methodology to accomplish this kind of mapping? I have a pretty good idea...but, some added advice and / or help would be appreciated.

Thank you.

 

[scubasean]

I am a current DM candidate that has been diving for the past ten years...(yes, I decided to go for my DM after some years of diving). I only have a few items left to complete on my DM...one of them being my mapping project.

Now the mapping project is described in the DM Padi handbook as a routine cross sectional, fin kick, depth marking, grid pattern...to and fro over the terrain...with a dive buddy...of course there are other ways to map a section of underwater terrain. My point here is that the book gives a rather cursory overlook that is not all that helpful.

I spoke with several instructors and they all give me differing answers on the 'best way' to accomplish mapping some underwater terrain (a quarry in this case).

My current instructor wants contour lines indicating depth of every 5 feet...contour of terrain etc. His method requires marked balloons, a team of divers, and a survey compass to triangulate to each balloon on the surface.

My question: I think I am almost fulfilling a navigation certification on top of my DM mapping project. Has anybody else worked on their DM mapping in this format? Anybody have a good methodology to accomplish this kind of mapping? I have a pretty good idea...but, some added advice and / or help would be appreciated.

Thank you.

First, I would listen to the requirements your instructor sets forth, and fulfill them, however you desire. But fulfill them you must, if you want the DM cert.

One of my friends recently completed his DM and related having to do a grid such as you describe. Took him 20 dives or so, by himself. Back and forth many times, taking notes and mapping on a grid.

 

[MikeFerrara]

The purpose of the mapping excersize is to create the type of map that might be useful to a diver who is new to the site or to you when teaching, supervising or briefing divers at the site. It also provides the candidate with some experience in planning a project and conducting task oriented dives.

It doesn't need to be a reliefe or topigraphical map and you sure don't need depth every 5 feet. Spending 20 dives doing that doesn't make any sense to me. How detailed it needs to be would depend on what a diver or a supervisor would need.

If I asked a DM candidate to map a quarry used for training that was 10 achres of flat mud bottom with little structure with 2 or three wrecks placed for divers, some training platforms, I would expect a map showing where those things were and giving enough information to find them.

 

[Diver0001]

I am a current DM candidate that has been diving for the past ten years...(yes, I decided to go for my DM after some years of diving). I only have a few items left to complete on my DM...one of them being my mapping project.

Now the mapping project is described in the DM Padi handbook as a routine cross sectional, fin kick, depth marking, grid pattern...to and fro over the terrain...with a dive buddy...of course there are other ways to map a section of underwater terrain. My point here is that the book gives a rather cursory overlook that is not all that helpful.

I spoke with several instructors and they all give me differing answers on the 'best way' to accomplish mapping some underwater terrain (a quarry in this case).

My current instructor wants contour lines indicating depth of every 5 feet...contour of terrain etc. His method requires marked balloons, a team of divers, and a survey compass to triangulate to each balloon on the surface.

My question: I think I am almost fulfilling a navigation certification on top of my DM mapping project. Has anybody else worked on their DM mapping in this format? Anybody have a good methodology to accomplish this kind of mapping? I have a pretty good idea...but, some added advice and / or help would be appreciated.

Thank you.

Part of the point of the mapping project is for you to discover what works and what doesn't. Try different things and see what works for you. If you make "mistakes" that costs you a dive then that's called learning.

Here's what I did with my buddy:

We used a reel 50 metres long with little knots tied in the rope every 5 metres. My buddy took one end if the rope and starting at a given location he swam out in a straight line away from shore using the compass. When he got there he waited while I swam towards him and reeled in the the line again. At every knot I noted the depth on a slate. No fancy graphs, just a row of numbers.

Then we moved 5 metres to the left or right and did it again but this time going the other direction. In one dive we were able to map depths over a 200-300 meter length like this (40-60 data points). The area we needed to map had a total length of about 5000 meters like this so that's 23 dives to map depths. In total we didn't do 23 dives because we realised early on that the bottom after a certain depth had a uniform shape and so we ended up actually doing something like 8 dives to map the area and another 2 to verify that the bottom was indeed uniform after a certain depth and 2 more dives to verify the location of the 100 or so reef-balls in the area we were mapping. We also wasted 2 dives on things that didn't work.

With the raw depth data I used a computer program to draw depth lines on a white background and then placed our reef-ball picture in the correct location on the map and colour coded the depths. After that I added shore features etc. The map looked ok and it was accurate.

And pick a place to map that you don't like I was so sick of that divesite by the time we finished that I haven't been back since.

R..

 

[NEWreckDiver]

The purpose of the mapping excersize is to create the type of map that might be useful to a diver who is new to the site or to you when teaching, supervising or briefing divers at the site. It also provides the candidate with some experience in planning a project and conducting task oriented dives.

It doesn't need to be a reliefe or topigraphical map and you sure don't need depth every 5 feet. Spending 20 dives doing that doesn't make any sense to me. How detailed it needs to be would depend on what a diver or a supervisor would need.

If I asked a DM candidate to map a quarry used for training that was 10 achres of flat mud bottom with little structure with 2 or three wrecks placed for divers, some training platforms, I would expect a map showing where those things were and giving enough information to find them.

As Mike said here, It really needs to have enough information on it that would allow you to give a detailed breifing of a area where you might be leading divers.

Depth every 5 feet seems extreme overkill, I would give general depth unless the area has a significant hill or mound underwater.

Good Luck to you.

 

[cortez]

After a few interesting ideas on how to complete this, I found the grid pattern the most simplistic. One thing I would like to add to Mike's list of objectives for this exercise is site familiarity. As a DM you will inevitably be leading divers on tours of sites, either in classes or in Discover Local Diving. I always thought I was good at finding my way around dive sites. I didn't realize how much making a map of a site could help that. I feel like I know every inch of the quarry I mapped for my DM. I give my best tours in it - keeps customers happy!

 

[oceancrest67]

Yes...my instructor wants contour lines on the drawing showing features...every 5 feet. I debate this in the sense that a mapping project for a quarry needs to show other divers significant features, sunken platforms etc.

Most people that have responded have mapped areas using the old fashioned buddy system, slate, reel and compass headings to and fro at depth.

My instructor is not making me map the entire quarry...just an area of it near an entry point.

I was just wondering what other methods other divers have used.

Thanks.

 

[Dan Gibson]

Don't you feel contours are very helpful in showing new divers where to stay away from (i.e. deep areas they are not yet trained to handle). This info also helps relate map info to a diver while using natural navigation. I think they can be very important.

Some of my buddies went all out on their map.
http://www.bluesprings.addr.com/Lake_Map.jpg There is also an awesome 3D model of this quarry they did as well. They spent all winter diving to get this info. It was time consuming and these DMS got a lot of diving experience. If nothing else, no one else knows the quarry as well as this group of DMs. You could put this bunch in the quarry blindfolded and ask them to open there eyes. They would a real good idea of where they were. Within a few seconds of swimming around to confirm, they would know exactly where they were.

Yes...my instructor wants contour lines on the drawing showing features...every 5 feet. I debate this in the sense that a mapping project for a quarry needs to show other divers significant features, sunken platforms etc.

 

[oceancrest67]

Yes...contour lines are important for a map to show natural terrain...I just do not feel that using balloons, a surveyor compass to triangulate each balloon...and a team of divers...I just think he is asking overkill for a section of a quarry. Then again, he is making me work at doing this...and, in this sense, I understand that learning something new is worthwhile. Oh well, I will figure it out in good time.

Alex.

 

[pt40fathoms]

3 to 6 hours of true bottom time is all you should be spending on this project. About the same amount of time topside, for planning the dives and methodology to be used. Any more than this and you are spending too much time on this project. How much time you spend making it look pretty is up to you, but this is where most people fall short. They have lots of data, but just do not present it well, so don’t rush this final step.

I would use a combination of techniques. Floating markers from **prominent** features and getting accurate bearings from a fixed place on shore is a first step. Using a 100-foot cloth measuring tape in a reel, combined with a compass and your depth gauge to get contour lines of the bottom leading to those prominent features would be step two. Distances with headings to lesser features around the prominent ones, using the prominent ones as start points would be step three. Finally, combining all this data onto a map to complete the project.

It’s really not that hard, but it does take time to plan. Once you have a plan, you can then attack this project with your dive buddy, preferably a fellow DM student, and complete this project with pride.


--text added--

I've added the Map I made a while back, using the techniques listed above. It's in PDF format, so you should be able to open in. I used a CAD program to create it, and it is to scale. I used contour lines at 100 foot intervals, which is what I was asked for back then.

Hope this helps.