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Scuba Diving With Gps


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SCUBA DIVING WITH GPS:

I'm using GPS data underwater...and no I'm not going to tow around some floating antenna attached to a cable. I gain GPS data...only "as needed" for the purpose of

"marking" a position...or "keeping an eye" on the boat or other objective.

I do this using a magellan hand-held unit. The method requires no elaborate pre-dive set-up, or equipment. It is a "deploy and recover" method, whereby the

GPS (in a clear housing)...is "dropped" (while attached to a line)....ascends rapidly

(positively buoyant)....gains signal....is pulled back below to find that the data is still displayed on-screen. Question: On deployment...doesn't the housing drift to

a distant location, rendering the data innacurate? NO... the housing ascends quickly, and the diver limits the amount of line that is playe out.

Question: Wouldn't it be better to attach some kind of cable thingy to a GPS that's affixed to a float, or somehin'? NO.... I like most divers, have no desire to tow

around a cable/antenna arrangement. This project has been primarily an academic project...not a financial one. **Important: preconceived ideas are natural, and common regarding this subject. The simplicity of the concept can be deceiving...it is an astoundingly effective method. thanks

Edited by mtn-man
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I like the idea GPS diver. Funny that you mention towing around an antenna. My father, who boats me out to many dive locations, often follows me around, keeping me in view on his fish finder. It's very easy to pick up a diver on a good fish finder. I show up bright red, because of the density of my weights, tanks, etc. Since I've been geocaching we've been devising ways he can broadcast my coordinates to me. In a way, that would be like towing an antenna with no line or anything.

 

My question was how much weight must you add to offset the positively buoyant GPS unit? Or can you offset this mostly by using a leaded line for retrieval? What sort of line do you use? How long must you wait for your GPS to acquire a signal and how in the world do you know when your GPS is on the surface if the visibility is poor, or if you're down quite aways?

 

Personally, I am not that familiar with high-end GPS equipment, so maybe most of these issues are solved by that. Not to be contrary, but it doesn't sound to me like this method could be considered much more accurate than taking a reading before submerging and trying to estimate how far you've moved. All things considered, current, tides, drift etc. accuracy would be a very general term. Not that towing an antenna would be accurate either, for the same reasons.

 

I guess that knowing your depth would be very useful when you deploy your line, allowing you to deploy only as much as you needed, thereby limiting drift. But then you must have something on your line to let you know how much you've let out, some sort of color coding every few feet or something.

 

A daunting task, underwater global positioning. Good luck.

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This sounds interesting. It would be great if it was in a housing that you could push the button and mark a waypoint, otherwise, you copy the coords on a slate. To answer a previous question about how you know when it reaches the surface: think about it....it will feel slack, and you just need to feed enough line to meet the current speed for it to stay on the surface.

Been thinking about getting back into my old hobby....

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These are some valuable, and often heard points to consider. I don't have a problem with the unit drifting to a distant location...the unity deploys very rapidly...it is very, very obvious when the unit hits the surface(even in poor vis)

because the diver suddenly feels a lack of tension on the line. Regarding your comparison to simply making a "mark" just prior to submerging...this is used at any time during a dive....only "as needed". Divers often need to avoid surfacing...even at a depth of 25 ft. or so, I truly do not want to surface until the end of the dive. Type of line? I've been using a kind of tangle resistant crab trap line (fm. Kmart of all places). I'm thinking about trying "running rigging" line as use in sailing applications...very thin, yet strong. **Note: Most of the applications in this concept can be done without switches in the housing. I've added switches to a housing which gives me the astounding ability to scroll through a list of waypoints...instantly viewing the bearing and distance to each (at bottom of display). **(all based on a single deployment/recovery of the unit) This data has proven to be as accurate as "go to" data. (I often display a primary go to on the lat./long. screen...by changing the default setting....to display "bearing" and distance" (which in this case refers to go to data....back to boat, etc.) *This concept is intended for avid divers and research divers...it is not a theory...it is an application that I've used on scores of dives with great accuracy. The concept can be learned on land by covering the antenna with alluminum foil (to simulate signal loss when submerged) I'm currently writing a second feature article on this concept...co-authoring a specialty course (at the invitation of a major certification agency) I will be starting the first training cycle with this "diver gps" with a group of public safety divers in a few weeks. **This is a "niche" subject that is not likely to put too many $$ in my pocket, but it is interesting to endeavor to add to the methods used in scuba navigation. It is simple, but without a certain level of promotion and training, it cannot make it into the diving community. Thanks

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Could you not download your track info and get waypoints from it ?

When you lose signal and reacquire you will get large jumps,but maybe you could

extract the time from the track as well,and jot down the time(from your watch) and sync

it with the track data.

Seatrout

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EScout wrote

To answer a previous question about how you know when it reaches the surface: think about it....it will feel slack, and you just need to feed enough line to meet the current speed for it to stay on the surface.

 

What I'm wondering, EScout, is how much positive buoyancy is necessary to allow you to feel the slack in the line? One pound? Three pounds?? Where does one keep this buoyant little bugger when it's retracted? Floaty things placed in pouches or pockets tend to adversely affect one's swimming. What size is this unit?

 

gpsdiver wrote:

Regarding your comparison to simply making a "mark" just prior to submerging...this is used at any time during a dive....only "as needed". Divers often need to avoid surfacing...even at a depth of 25 ft. or so, I truly do not want to surface until the end of the dive.

 

Yes, I never want to resurface during a dive either, regardless of how shallow it is. What I meant by that was only in those cases where a diver is moving predominately in one direction and could estimate the distance travelled based on kick cycles and whatnot.

 

Crab trap line is leaded, I believe. At least, shrimp trap line is. Which means it's negatively buoyant and very suited to what you're doing with it.

 

gpsdiver wrote

I don't have a problem with the unit drifting to a distant location...the unity deploys very rapidly

 

I see what you mean. You let it pop to the top, wait a few moments, then pull it down. Even if it drifted a little from the moment it acquired the signal you would be able to tell exactly where it was when it first acquired the signal, making it very accurate.

 

Again, I'm curious, what size is this unit? You've reiterated several times that any idea anyone might think of has already been thought up by you, but I was thinking that if someone simply released an antenna with fiberoptic NETr cable connecting it to a waterproof GPS..... Well, anyway, hehe, what size is it?

 

P.S. Because I want one!

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Hmmm...

  • pushing products he's selling on ebay
  • profile pushes self-published book
  • profile links to webpage pushing his products
  • post doesn't relate to geocaching (although idea could be applied to caching)
  • hasn't found any geocaches
  • hasn't expressed any interest in geocaching or relating his ideas to geocaching

Just an observation.

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Mopar wrote:

Hmmm...

pushing products he's selling on ebay

profile pushes self-published book

profile links to webpage pushing his products

post doesn't relate to geocaching (although idea could be applied to caching)

hasn't found any geocaches

hasn't expressed any interest in geocaching or relating his ideas to geocaching

Just an observation.

 

And Bingo was his name-o!

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I have been "ungeocached" by a member it seems. Yes...I would be classified more as a diver than a geocacher. Diving and geocaching don't always go together...but for those who dive it is an interesting topic. Regarding ebay...yes I do have products on ebay, but you can be certain that I've spent more promoting

the diver gps concept, than I've ever received from any sales. I end up using the small profits for printing costs for products that I distribute free of charge to

various agencies involved in research and training.

There is a natural tendency towared skepticisim when someone begins discussion of a topic like this. The reality is that only a small percentage of readers will have an actual use for the application. Let me answer a few of the above questions

*Buoyancy: The housing can be made slightly negative with the additon of 2 lbs of lead....I've found that I prefer to securely attach the item, and skip the use of the lead. *Switches: The diver can observe 1 go to...and retain the ability to

"mark" locations without switches *I have added switches(by sending the unit to

a housing manufacturer) As mentioned in a previous post...this adds the ability to scroll through a list of user waypoints, observing the bearing and distance to each

(based on only 1 deployment/recovery. **Important: The evolution of a topic like this is very, very predictable. Someone always (without fail) steers the topic toward a predictable method involving the use of a data cable/ floating antenna.

**That's fine for the rare person willing to do so....this concept is intended to allow the diver to dive as normal...without cumbersome gear or pre-dive set-up.

**someone mentioned the concept involving a floating unit, and the downloading of the track post-dive. This also has been done, and may be effective for some.

My concept, however is more of a real-time operation....allowing for the use of GPS data during an ongoing dive. **Again... if some feel that this is "off topic" for geocacing...for most this is probably true. However, for someone who is both an avid diver, and a geocacher, this may open up new avenues. **Keep in mind that very, very few people in the world have ever used GPS data underwater. This concept allows GPS data to be used with only a housing and a Magellan hand-held unit. ***If you have a Magellan hand-held...give the concept a try on land.

How? simply use alluminum foil to obscure the antenna area(to simulate submerged periods) ...walk about simulating the start of the dive, and the deployment and recovery(remove and replace foil) The concept is easily

learned and proven on land. **Again...this topic will always....always...return to the discussion of the data cable/antenna rig. You can be certain that it is difficult to encourage a diver to try anything that's not been commonly seen in use...getting someone to use one of those type rigs would truly be a tough sale.

*There is also an interesting psychology that follows this type of topic. Humans are so naturally skeptical that someone with a strong voice of skepticism will

join the fray, without having seen...or having tried the method. If anyone reading this is a journalist(who happens to be coming to the Fla. Keys soon) I'd be happy to demonstrate and prove the method. The real "profit" that I've receive from promoting this concept is in finding some very interesting contacts within the diving industry who are helping to promote the concept. I can accomplish very little on my own. **Now...watch carefully as this topic will certainly swing toward the cable/floating antenna arrangement. Oh well.....

Edited by mtn-man
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:( I should add that in reading the guidelines...I see that any mention of sales of items should be restricted to the garage sale area. I should have been aware of this, and will be sure to follow that guideline in the furure......thanks
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Well, I think the concept is pretty interesting. Scuba caches I've read about (none near me, but I'll be rectifying that this summer) generally use the GPS coordinates as a point of entry, then rely on underwater navigation with a compass bearing and depth references to get to the actual point. However, I could see that this might work if you are looking about for a spot and want the coordinates so someone could enter directly above the cache. Wonder how it would work to put the GPS on a float along with the flag that most divers would be towing anyway.

 

Adding one thing here, in using a float, I meant to use tracking, not some sort of remote display underwater, which I guess the original poster had also considered at some point, according to his web page.

Edited by writer
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One great disadvantage of this method, is that you only gain the GPS data after the dive. Using the "deploy and recover" method that I've described, allows for data use both during, and after the dive. Yes it can be helpful for geocaching, but I'd suggest that the avid diver might want to take advantage of the full capabilities of gps.

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There's no place for insults and rudeness. We're all friends here. Gpsdiver is a good guy, trying to bring a novel idea to a place where it might be put to good recreational use.

 

[Mean insults were edited out after further review]

Edited by LeatherKnight
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Can you please give direct examples of how I am being so rude to others?

That was not my intention. I was simply trying to stimulate others to steer away from the predictable direction of this topic. I did not at all intend to be condescending in doing so. Your repsonse however...is intended solely to be

insulting and rude. The absoloute simplicity of the concept is the point. There is no intent to portry it a some astounding scientific device. In fact...the odd fact is that the "research" that you refer to...has not given much to the average research or recreational diver. It is very, very difficult for people to consider trying something that they have not seen in widespread use. I think that if you will look over my posts, you will find that your response is very exaggerated. It's odd that you acuse me of a form of rudeness, while your response is completely over the top. I will try to avoid sounding "preachy" in spite of the fact that, yes...these conversations always do gravitate toward predictable outcomes. You, however...may want to avoid being purposely insulting. These also is a predictable reaction from a very small minority of respondants....any time that a

new avenue of thought or tactic is proposed. You many very well be a diving "expet" and that can sometimes be where the problem begins. Experts in a given field, are often hesitant to listen to the advice of others. Again...this is not about amazingly impressive equipment or concepts. It is about taking advantage of the height of simplicity in fact. Your reaction at theis point may be to: 1)

Rail against me even more loudly than before 2) perhaps respond by saying something like..."Hey...maybe I did overstate my case...sorry." Again...I will try to avoid soundy "preachy" which is easy to do in this format. A final thought...

Did you hear the story of NASAs past attempt to develop a pen that would write upside down...that would write in zero gravity? Supposedly, an Astronaut discussed this with a Soviet Cosmonaut, who is said to have replied, "Oh...we just use a pencil." My concept is the "pencil." My concept is the minimalist's approach.

A ran into a guy who had a similar reaction to yours (he was an N.E.D.U.)diver...he railed about the great expense and complexity of the fantastic system of "diver gps" that his unit used. He failed to understand that the complexity of set-up...expense....and lack of practicality in the real world was not something that would benefit most research or civilian divers. I have no doubt that you are an expert of the highest degree...otherwise you would have no reason to react with such anger toward my simple approach. Now......play nice!!

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I forgot someting! To the above person who was so critical of my "diver gps" posts...I propose a challenge. (All done in fun... a good natured challenge)

I propose that you post your proposal for the best method for using GPS data underwater while diving. Not simply a theory...but something that a diver can truly use. I will then describe my method in exacting detail also. *This will not be about the future...it will be about now...what can we do now. Again...this is not intended to be a mean spirited sort of competition. You simply spell out your best suggestion...and I will spell out the details of a method that I've been using for about 3 1/2 years. Now....if you don't agree...please avoid any predictable or angry response. Controversy is a natural thing when it comes to talking about new ideas and concepts. YES! YOU HAVE BEEN CHALLENGED! *hey...this could be fun!! :(

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I am only interested in the concept and application and thank gpsdiver for bringing this to our attention. The idea has merit and to me seems the easiest and best means of GPS use while diving. Since I like to make things and tinker (and I used to make various stuff for my personal use in my diving days in the past), I would like to see photos of the container/float/housing, and suggestions on materials, how to, etc. Being a forum to share ideas, this is quite appropriate and expected. And if you are going to make these and sell them commercially, I would like to do the personal-time-involved-to-make vs cost-to-buy comparison and maybe buy one. Thank you.

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Thanks for the friendly reply. One of the amazing things about this, is the low cost of the housing (by the way...I'm not selling them) I use the Otterbox 9000

"clear" model. It retails for between $10 to $20 dollars, and is rated to 100 feet.

This might be a great general purpose cache container also. The best price that I've found is at aaacamera.com ($9.69). Be sure to get the "clear" model if using for "diver gps." I don't think there's enough market available to manufacture a profitable model. I simply take the above mentioned container...and send it to a housing manufacturer(along with the gps)...to have the switches installed.

The installation was around $100...seems expensive, but is well worth it.

**Without the switches you can view lat./long.- time - and a single "go to" all on one screen (Magellan sportrak, sportrak Map, Meridian....must customize the position screen to display "bearing" and "distance"...(refers to a "go to")

In this application...you deploy and recover the unit...make note of any lat/long to be saved....and enter manually post-dive. (while also having the bonus of viewing the "go to" back to boat, start point , etc.) **Got Switches? By adding switches you gain 2 added functions: 1) the ability to press 1 or two buttons to "mark"

an area(marks area of last deployment). 2)**This is a big one...based on only 1 deployment and recovery cycle...you can scroll through a vast list of user waypoints...making note of the bearing and distance to each! Most people won't need this, but it's a great feature for avid divers or research types. You can view photos at my informal site at: http://groups.msn.com/divergps (enter as shown...no "www") The funny thing? Although I love this concept, I would never invest a great deal of money in it. It is far too difficult to get people to try something different...and it's kind of a niche application. I think it is of note, however, if you consider the fact the underwater GPS use is very rare. I'm starting with the assumption that a diver does not want to bother with expensive or complicated equipment. Thanks for your interest. The internet is amazing in that it allows for the sharing of these kinds of topics with people we've never met. I've made some very, very important contacts this way.

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I was not trying to be critical of your GPS diver posts. I was not trying to be critical of your "GPS in a waterproof housing" idea. I was pointing out how condescending you were being towards anyone with a simple question. I was not trying to be insulting and rude. Perhaps it is a natural reaction to being talked down to.

 

gpsdiver wrote:

These also is a predictable reaction from a very small minority of respondants....any time that a

new avenue of thought or tactic is proposed.

 

Again, I did not react adversely to your idea. Just to your attitude that such an idea gives you some sort of license to demean other peoples' opinions. I haven't heard one person scoff at you and say "Underwater GPS is impossible." Yet you act like you're constantly expecting such a response, and throw out rebuttals like speedbumps.

 

Though, as you say, sounding "preachy" is easy to do in this format. This might be why you sound like a patronizing mad scientist and I sound like some insecure jerk in a glass house. :( The lack of tone and facial expressions can make forums like this war zones. I'm starting to think that is what has occurred.

 

I like your good-natured challenge. I definitely accept. I'll table my idea within 2 days. Feel free to post yours in exacting detail. No offense, but I think that several people have been waiting for you to list things in exacting detail since you first posted.

 

This may be fun!

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I use a waterproof float for the GPS for logging tracks on recreational dives and for logging tracks when performing search and recovery dives for Plymouth Fire Department and the Plymouth County Technical Rescue Team.

 

The photo,coincidentally, was taken for the dive made in order to access the "Oh Island in the Sun" geocache on November 10, 2003.

 

50f4795e-e16b-4b4d-82ec-78d45b5afda5.jpg

 

You can also check the GPS Mapping for Underwater Sites webpage.

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Slick deal, wreckdiver.

 

From what I've learned, GPS diver is right about the deploy and retrieve method being the only feasible one. A minimum of 2 sonar buoys is necessary for any degree of accuracy, with 4 being needed to cover an area of any size.

 

Hehehe, but what really cracks me up is seeing his name on many other sites, and seeing how many people get the same impression I got about him at first.

 

I was wrong. Enough already!!! :( I can admit it. I should have done the research I did after your challenge before I responded at all. I can see now exactly how such a device works, and I can understand how accurate it would be.

 

If I had seen a picture like Wreckdiver's in the beginning, it would have been more clear. For some reason, I was picturing a basketball-size underwater mine-looking deal. Funny what an imagination can do. :D

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gps diver wrote:

Thanks for being a good sport about the whole thing. I think it has gotten easier to describe the concept as I've found out what the usual reactions...questions...and objections are. Thanks!!

 

You're quite welcome, gpsdiver. Still, I am eager to read your "method in exacting detail." I've learned a lot from other sites, many of which you frequent, but I have yet to read about the whole device, from pre-dive preparation to actual use while diving.

 

I don't think I'm alone in wanting to hear all of this. I personally plan to use it to plant an underwater cache in the Hood Canal region in Washington State. Include any information you think is relevant, if you would.

 

Thanks in advance!

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Slick deal, wreckdiver.

 

From what I've learned, GPS diver is right about the deploy and retrieve method being the only feasible one. A minimum of 2 sonar buoys is necessary for any degree of accuracy, with 4 being needed to cover an area of any size.

 

Hehehe, but what really cracks me up is seeing his name on many other sites, and seeing how many people get the same impression I got about him at first.

 

I was wrong. Enough already!!! :( I can admit it. I should have done the research I did after your challenge before I responded at all. I can see now exactly how such a device works, and I can understand how accurate it would be.

 

If I had seen a picture like Wreckdiver's in the beginning, it would have been more clear. For some reason, I was picturing a basketball-size underwater mine-looking deal. Funny what an imagination can do. :D

I won't comment either way as I have used the pictured assembly as a surface array since I constructed it and have not attempted to retrieve it from the surface during the dive by forcing a descent, or bringing it with me during the dive and attempting to deploy it from depth.

 

I chose a surface array for several reasons:

 

1.) Regardless of claims of watertight integrity, ALL water-tight containers fail at some point. Taking photographs of deep water wrecks for publishers taught me that lesson well.

 

2.) Pulling a positively buoyant object from the surface places equal buoyancy changes upon the diver so neutral buoyancy is compromised upon release and/or retrieval.

 

3.) Using lift bags fairly extensively for recoveries, I can attest to the hazards of extremely buoyant objects at depth.

 

4.) There is no way to mark or record a waypoint electronically ("GOTO") if the GPS is in a rigid container.

 

5.) A GPS carried at depth will not receive a signal and upon deploying at depth, the diver will not have any idea as to whether the GPS has acquired a signal, how accurate the signal is, or how long the waypoint was averaged.

 

To accurately mark a submerged waypoint without dealing with the detailed issues, I find that it is more feasible to drop a Pelican Float Marker Buoy and record the waypoint using the GPS at the surface in conjunction with the tracks.

 

As a side note, some of the divers in my cadre have logged dives on the Andrea Doria, the U-869, and the Monitor. During decompression, one has a LOT of time to find ways to entertain oneself.

 

One of their favorite past times on recreational dives is to "Reverse Depth Charge" jet-skiers that use a dive flag as a high speed turnaround. This simply involves taking a water-filled two liter bottle, inverting it, partially filling it with air, capping it and then releasing the positively buoyant container near the offending jet-skier. During ascent, the flexible bottle expands and ruptures violently as the external pressure decreases.

 

But that's another story...

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Wreck diver wrote:

2.) Pulling a positively buoyant object from the surface places equal buoyancy changes upon the diver so neutral buoyancy is compromised upon release and/or retrieval.

 

That was something I had questions about earlier. I think Gpsdiver will explain how he does it.

 

I like your anecdote about the reverse depth charge! I've done similar things, and I know how hard keeping neutral buoyancy is when you're messing around with things that float. We call it "wrestling the invisible octopus." Since my friends and I dive in dry suits, occasionally someone will get distracted or out of position and find himself floating towards the surface. As the water pressure decreases at lesser depths, the air in the suit expands, making the diver even more buoyant. The ensuing thrashing that occurs while the diver tries to get the air to exhaust through his release valve while fighting to maintain his depth looks for all the world like someone struggling against an unseen adversary.

 

So that's a surface array that you don't retract, huh? So you tow it along as you swim. I hope no jet skier tries to use that as a high-speed turnaround!

 

How deep do you think a watertight container could be depended upon? Or, a waterproof GPS, which is used by the military and available for civilian purchase?

 

Wreck diver wrote:

5.) A GPS carried at depth will not receive a signal and upon deploying at depth, the diver will not have any idea as to whether the GPS has acquired a signal, how accurate the signal is, or how long the waypoint was averaged.

 

That was another of my questions. Gpsdiver experiments with his GPSr by blocking the signal with aluminum foil, then uncovering it, giving him a fairly good idea of how fast his unit acquires a signal.

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Since my friends and I dive in dry suits, occasionally someone will get distracted or out of position and find himself floating towards the surface. As the water pressure decreases at lesser depths, the air in the suit expands, making the diver even more buoyant. The ensuing thrashing that occurs while the diver tries to get the air to exhaust through his release valve while fighting to maintain his depth looks for all the world like someone struggling against an unseen adversary.

My technical diving equipment is 126 pounds on the surface, but slightly positive when both tanks drop below 500 PSI. Because of the weight, a drysuit is mandatory for redundant back-up.

 

I took a picture of the Bottom Time travel bug with some of the technical rig:

 

d4b502e9-fec2-4241-a967-0d85e257be48.jpg

 

As far as depth rating goes, I don't forsee any guarantee that will hold water, so-to-speak. Simple physics: if it goes up, it must come down, if you put it in the water dry, it's eventually going to come out wet.

 

One of the reasons I've thus far declined creating a free-dive/SCUBA cache.

 

Though I have felt my logic sound for my own applications, I can't attest to ever trying gpsdiver's concepts. I have a dive team drill coming up shortly, so I will probably attempt some of the concepts to see an improvised application in the environment that I'd need it.

 

Public safety is in constant evolution, so gpsdiver's ideas have potential to revolutionalize in-water waypointing if it pans out.

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Wow, nitrox diver!! And using argon gas in the drysuit! How much warmer does argon gas keep you in cold water? I've always wondered.

 

Wreck diver wrote:

As far as depth rating goes, I don't forsee any guarantee that will hold water, so-to-speak. Simple physics: if it goes up, it must come down, if you put it in the water dry, it's eventually going to come out wet.

 

One of the reasons I've thus far declined creating a free-dive/SCUBA cache.

 

Well put, Wreck diver. My idea was for a cache that consisted of entirely waterproof items, including a laminated all-plastic log and an underwater marker.

 

I think that Gpsdiver's deploy and retrieve method is technically sound, and perhaps, if there is a market for it, might be modernized even further with waterproof GPS units. One thought is to deploy just the antenna device with cable relaying information back to the GPS, allowing the diver to mark waypoints and set go-to points, and still have the flexibility of retracting the antenna at any point with the cable being stored as one piece with the GPS unit.

 

If there's one thing you can be sure of, people want to know where they are, even if they're underwater.

 

Smooth tank set-up, by the way. I'd like to see some more of the pros gear, if you have more pics.

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The GOTO thoughts under water are interesting as any GPS once nav is lost should not show any navigation type information (or capabilities at all) as basically the no nav data then any other functions should be disallowed so as not to cause irrelevant and generally incorrect output.

 

A GPS carried at depth will not receive a signal and upon deploying at depth, the diver will not have any idea as to whether the GPS has acquired a signal, how accurate the signal is, or how long the waypoint was averaged. That is a very relevant comment as any receiver that pops the surface won't get an immediate position, how long will it take? well that will/might vary, at times.

 

Cheers, Kerry.

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What Kerry says is true, that popping to the surface, it may take a while to get a position, and you don't know how good it is. However, I just tried my Meridian in the house: 5 sats, 30' EPE. I put foil over the antenna until all sats were gone and it said it is looking for first satelite. The position lat and long still showed and pushing Go To allowed me to set a waypoint. This tells me you can reel your floating GPSr back down and read the coords, and a track point should show at this location.

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I'll try to answer some of the questions of the last few posts, based on my experience with the "deploy and recover" method.

1) Question about whether the go to data can be used after loss of signal.

The Magellan models(unlike many others)...will continue to display data based on the last acquired signal...in spite of the fact that signal is lost (as when pulling the unit below). This means that A) If I have customized the position screen to display

"bearing" and "distance"...I can display 1 go to on that screen. :blink: With the addition of housing switches...I can scroll through a list of user waypoints, as the bearing and distance to each appears at the bottom of the display.

 

2)*statement that ALL containers may leak: perhaps true, but this has not stopped divers from taking expensive cameras underwater for decades

 

3) Statement about the effects of deploying and recovering a "buoyant" object

(the container). The lift is so slight (can be made negative with only 2 lbs)...that this has never...ever been a factor at all.

 

4) statement that there is no way to record a go to electronically if GPS is in a

rigid container. Method A) diver jots down data on slate...enters into gps post-diver Metghod :ph34r: *(housing with switches) diver uses 1 or 2 switches 2 "mark"...

makes note of what 01...02...03, represent...and gives a name post-dive

 

5) suggestion regarding not knowing if the gps has acquired signal. This is a valid point, but one that can be addressed... **Important: if practicing on land(by covering/uncovering antenna with foil...it can often seem that the unit regains signal remarkably quickly. This, however, is only true if the unit has lost signal for around 4 minutes or less. In actual use...it is very, very important to allow the unit to surface for a minimum of 60 seconds (to reacquire from a "cold start")

The diver may leave the unit on the surface for longer periods of time

***Imprtant: Diving at relatively shallow depth...want to have signal available to you in about 4 seconds? The unit can be "towed"...leaving it on the surface...when gps data is needed ....quickly pull down...view data...release...swim to next objective. **I want to be very, very careful not to sound like "Mr. GPS" here, but I would like for you to know that I have spent countless hours with this concept, both in the water and out. I promise you that this is not a gheory...this is a very usable concept. If you have a Magellan unit (particularly...Sportrak...Sportrak Map/Pro..Meridian) ...take it for a spin on land. Just use foil to cover and uncover the antenna as you walk about a testing area. **It is important to be skeptical... but please be careful not to look for a reason that the concept won't work. In testing...I've tried to create situations to "make" the concept not work...to make it fail, and have been surprised at the results. Why do I care? Because I am a great fan of diving...but I feel that the industry is very slow to change (case in point...the Nitrox debate of a few yrs. back) I know that a new concept will only be used, as divers begin to see other divers using the concept with good results.

The objections that I often hear are very valuable to me...these help me to remember to address these issues when writing about the subject, or when speaking to a group. * One of the most amusing responses, came from a guy who angrily emailed me to tell me that the idea would not work. Why? His dive areas are covered with Kelp! I hadn't thought of that one, but in his world...very valid point. Thanks

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HOW ABOUT A CHAT TONIGHT!!

I will be at my MSN group site tonight at 8:30 p.m. (Fla. Keys)

to chat about this concept. The MSN groups, require that you "join" in order to use the chat feature...so arrive a bit early to set-up. The group settings will give you the option of not receiveing emails, so don't worry about getting spammed.

An MSN prompt will also appear asking you to load the chat software if you don't aleready have it...you know...the "do you see the smiley face" thing?

The whole process is very quickly completed. Thanks

http://groups.msn.com/divergps then click on the "chat" link on left side

*p.s. These MSN groups are a nice way to set up a simple and free web site

Edited by gpsdiver
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Lets just say that there's nothing wrong with the concept but this string has again raised this dangerous functionality that some receivers have built in, that is the capability to navigate (or think/show they are navigating) when there are no signals to navigate with.

 

This function (undesiable capability) has probably seen more rescue helicopters sent in the wrong direction than one would like to think. Basically ground crews arrive, require a chopper, whip out the GPS, turn it on and basically realy coords on the screen as there can in some instances be no indication that the unit is actually navigating, acquired or not.

 

Really this little issue with some receivers should be plugged. Might not suit some "concepts" but a receiver that doesn't have a signal really shouldn't show a position at all as it can be extremely misleading and many resuce pilots these days are aware of this.

 

Cheers, Kerry.

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Well...that is the theory that the Garmin Corporation seems to go by. It seems that most of their units overwrite with some sort of "signal lost" message...disallowing the viewing of data...that is without signal. For this application it is kind of dumb luck that Magellan does not obscure the data. I do understand what your saying, however. All of the GPS manufacturers are careful to have disclaimers about using GPS as a sole means of navigation. I'm glad that I did have several hundred beach dives to learn to navigate, before ever using gps in this "deploy and recover" mode. The reality is that most divers don't dive often enough to even consider going to the trouble to try this. That's why my focus has been more towards working, and law enforcement divers. However, a diver that happens to also be a geocacher...seems to be a good candidate for the

idea. My first exposure to GPS was in the USN, in '79. I think we got an update about once per hour.

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I've got some photos at my MSN group at:

http://groups.msn.com/divergps Now let me make this next statement

without sounding like a know it all. I kind of feel that I'm past the testing phase of this concept. It's something I've been doing for several years...am beginning training with law enforcement...have been invited to author a certification program for a major diving certification agency. **I'm mentioning this not to "blow my own horn"...but to illustrate the fact that this concept has been largely accepted by those who have tried it. Thanks

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Kerry wrote:

Really this little issue with some receivers should be plugged. Might not suit some "concepts" but a receiver that doesn't have a signal really shouldn't show a position at all as it can be extremely misleading and many resuce pilots these days are aware of this.

 

Great point on this, Kerry. I ran into a problem yesterday. My batteries were getting just a tad low. Anyway, I lost my signal and backtracked to reacquire it. When I did, it said I was 400 miles away, in British Columbia, rather than Southwest Washington State. Yet, it claimed the accuracy was within 40 feet.

 

After giving the matter some thought, however, I realized that there was no way I could have been teleported by aliens to British Columbia. After all, everything still looked the same. Still, if I was a less savvy GPSr I might have spent days looking for the American Embassy, instead of just finding my truck and going home.

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Let me try describing what a typical dive with GPS might be like.

**Note: Their is more than one method possible for the "deployment and recovery" of the housing. In this description I will only describe a method that works in tandem with a dive flag.

I arrive by small boat at a familiear dive site. My Magellan hand-held unit has led the way. quickly dropping, I prepare to dive. The depth will be about 35 feet.

As I prepare my gear, I notice that the boat has swung about the anchor, and seems to have settled nicely into the current. I easily "mark" this point by holding the go to button down for 2 seconds...then pressing enter. (Magellan Map/Pro).

I place the GPS into a small, clear housing. The housing is fitted with 2 brass

rings, and clips securel to my BCD. I prepare my simple dive flag for the journey also. This is not a typical ball type flag (too much "drag" in wind/current)...this is a flag made from a sausage-shaped boat fender...the kind you see hanging over the side of a boat. Two large plastic cable-ties hold a 3 lb. dive weight at the bottom-center of the float....a plastic flag with a wooden shaft is mounted at one end...while the tow line is at the other. I begin the dive, pulling the flag as I go.

Although the wind is considerable, I scarcely feel a tug on the flag.

About fifteen minutes into the dive, I encounter a huge brain coral, positioned next to a small, but healthy patch reef. I decide to "mark" this position.

I simply take the line in my hand that pulls the flag....attach it to the GPS housing

(with a brass pin-clip)..."drop" the housing...allowing the line to slip through my fingers as the housing rockets toward the surface. It is obvious when the housing hits the surface because the tension on the line suddenly releases...I can even see the housing, almost directly overhead. I don't simply sit motionless as I wait for signal to acquire...I enjoy swimming slowly around the impressive coral head...amazed at how many lobsters reside there. I wait a minimum of 60 seconds...then reach up, pulling down on the line in a hand-over-hand fashion, the housing reaches my hands quickly, as the flag takes up the created slack line.

I make note of the lat./long. (either by switch, or by annotation...depending on whether housing has switches or not). The "go to" that is displayed shows that the boat is at bearing 130.... 175 yards. I continue diving for another 30 minutes, and decide to head back to the boat. I repeat the deploy and recover cycle and find that the boat is at 187...230 yds. (*I do not rely soley on the GPS, but try to keep an awareness of the boat's relative position by traditional techinques also).

I begin swimming on heading (187)...I'm holding the GPS housing with an extended right arm, making use of a compass that is mounted at the top of the housing. After several minutes I begin to notice familiar topography. I also notice that I'm at a depth of 33 ft. (the depth where the boat is anchored). Just as I begin to wonder if I've swum to far, I see the distant anchor line, stretched at an angle across the ocean before me. Before ascending I deploy and recover the GPS one last time. I'm just curious about the relative position to a few spots in the area. I could do this in the boat, but it's fun to have the capability underwater.

My housing has switches, so I go the the "user waypoint" area, and begin scrolling down through the list. As each waypoint is highlighted, the bearing and distance to each is shown at the bottom of the display. Wow! I'm only 620 yards from

Milton Reef?...I thought it was further than that. I notice that I'm at 083... and about 5 miles from my house (useless but rather amusing info.).

Another dive is complete. Another rare dive, making use of GPS data.

http://groups.msn.com/divergps MSN group site on this topic

Edited by gpsdiver
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<moderator mode>

 

gpsdiver, I think you have linked your msn site enough times.

I have also removed some of the commercial sections of your posts.

 

This is very loosely related to geocaching. It does bother me that the topic starter creates an account right before posting this topic, post about where he is selling items in that first post and still has not found a geocache yet. I'll let it continue since some geocachers are interested and this can benefit them.

 

Please watch the commercialism. When someone says that they are not trying to make money as much as you have then it usually means you are trying to make money. That is especially true when you talk about where to buy your stuff.

 

No reply, clarification or explanation is needed.

Please only continue the discussion.

 

</moderation mode>

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*(Note to self: A surplus of "zeal" often leads to poor communication)

Anyway... this thing sometimes is more of an excercise in communication than anything else. I've always noticed that I learn something from these kind of posts...but it can be repetetive. **regarding buoyancy...the housing that I use takes 2 lbs. to make it negative. I don't even bother to weight it anymore...just secure it to my BCD...thanks. **I have sometimes gotten comments about the fact that "mine already floats" etc. That probably won't help in this case because I'm taking the unit underwater and the switches would become compressed...I can't imagine that the salt water would do it any good either. Here's an odd fact about deploying the unit to the surface in a housing. I've noticed that when the GPS floats in a flat position...it doesn't seem to lose signal strength nearly as much as when held flat on land (surrounded by air....not water) I can't weight the container to make the GPS point up, as even a small amount of water coverage

(at bottom of GPS) causes signal loss. *Scuba Geocaching? Maybe some avid cacher out there will run with this concept and get a nice U/W geocahing group going. (beach diving would be fun) I noticed that orienteering is big in Europe.

Fort Lauderdale has some great beach diving areas, but I now live in the Keys

(very, very little beach dive potential) I know that some caches are already place in water...but how about making a day of it? A veritable beach diving/ geocaching

bonanza! *Safety first please! I will attempt to find a reasonable location for a sub-marine cache in the near future...it would be interesting to see how long it takes for it to be recovered. Thanks

Edited by gpsdiver
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This is a slick idea. It sure would beat popping to the surface to get a bearing.

 

I think that I'd want the line to be on some sort of reel, though. I've never liked dealing with lots of loose rope underwater.

 

As for geocaching, it makes perfect sense to use such a method for finding or planting a cache.

 

I use a Magellan 315 and it shows GOTO information based on the last time it had a signal.

 

Question: How near the surface does the antenna need to be to get a signal? Feet? Inches? or does it actually need to be AT the surface? The reason is that I was thinking of a small lift bag to help with the deployment, but would lift probably to a foot below the surface.

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My technical diving equipment is 126 pounds on the surface, but slightly positive when both tanks drop below 500 PSI. Because of the weight, a drysuit is mandatory for redundant back-up.

Looks like a pic of my PST104s rig! I've got about the same setup, and a lighter set with AL80s. Sounds like you and I need to go diving sometime, wreckdiver!

 

My question for "gpsdiver" is, why not just simplify, and use marker buoys? You know the kind, I hope... little lead weight on the end of some cave line, wrapped around a float? Can be used from surface or from depth.

 

The methods you're talking about with lines, antennas, etc., sounds like an entanglement hazard waiting to happen. Personally, I don't LIKE body recoveries.

 

And BTW, gpsdiver -- don't try to sell me equipment via email again. We try to play nice around here.

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