So. you swim behind a reef, or you swim into a cave/cavern, you are going to lose line of sight with the transponder and it will not know where you are.
Underwater GPS
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So. you swim behind a reef, or you swim into a cave/cavern, you are going to lose line of sight with the transponder and it will not know where you are.
I looked at the product mentioned above, at DEMA. It uses GPS technology in a surface device, located either on a dive boat or surface flotation device then communicates with the wrist mounted units on each diver using sonar. It didn't have a price as it is just now going into production. It was about the size of a typical wrist mount computer. Yes, as someone else mentioned, it tracks multiple divers and each can see the others as well as the host unit (dive boat). It also had a contour map of the dive area.
paddler3d
Guest
So. you swim behind a reef, or you swim into a cave/cavern, you are going to lose line of sight with the transponder and it will not know where you are.
Same argument can be made for a conventional GPS. You get into a valley and there is only one satellite overhead and you're GPS can't tell you where you are either.
Same for a radio as well. If you have a mountain in the way with the other radio you are communicating with, you aren't going to be communicating with that radio.
I agree there are limitations.
I imagine it would have lesser limitations on the deeper dive sites, i.e. NC wrecks.
THE UNIT DOES NOT HAVE TO RECEIVE THE GPS SIGNAL. soor for the caps... only the reference has to receive it. i dont know how this works but i have worked with items teat output the same data. you put a bouy in the water. you put in the wrist dc the pucouys lat/lon.
the wrist unit with a directional rcvr can provide the data to the dc as to the direction and range to the reference bouy. then calculate teh diver lat/lon from there. if i am not mistaken the renge for this is short i dont think it is good for 1000 yards perhaps a 1000 feet. this allows for high freq sonar xmssion. a fm smission can carry a lot of data including the location of the other divers. now how your position gets to the bouy for relaying i dont know. the diver is limited to the power he can carry. perhaps the bouy has directional array on it also. if so then it calculates where you are from it. if so i would guess that each diver has a responce pinger to id its self to the bouy. if it is close to accurate then it will be expensive. if it is accurate it will be really expensive. we used this technology on submarines for decades to track our se\lves on a acoustic or weapons range. as far as the map just an overlay sized to a screen.
i use a device from s\desert star probably 5-600 by now it is one pinger and a hand recver wirth signal stregnth meter that receives a pinger signal. check them out... ......desert star......
http://www.desertstar.com/Products_category.aspx?intProductCategoryID=7
lastly the divice may or not work well depending on where you use it. walls marine life algee can affect a sonar signal realy bad. if high freq is being used say 50khz a thernal layer can suck the sig straight to the bottom. but them that me be the science of the limited range.
kws ex sub sonarman
the wrist unit with a directional rcvr can provide the data to the dc as to the direction and range to the reference bouy. then calculate teh diver lat/lon from there. if i am not mistaken the renge for this is short i dont think it is good for 1000 yards perhaps a 1000 feet. this allows for high freq sonar xmssion. a fm smission can carry a lot of data including the location of the other divers. now how your position gets to the bouy for relaying i dont know. the diver is limited to the power he can carry. perhaps the bouy has directional array on it also. if so then it calculates where you are from it. if so i would guess that each diver has a responce pinger to id its self to the bouy. if it is close to accurate then it will be expensive. if it is accurate it will be really expensive. we used this technology on submarines for decades to track our se\lves on a acoustic or weapons range. as far as the map just an overlay sized to a screen.
i use a device from s\desert star probably 5-600 by now it is one pinger and a hand recver wirth signal stregnth meter that receives a pinger signal. check them out... ......desert star......
http://www.desertstar.com/Products_category.aspx?intProductCategoryID=7
lastly the divice may or not work well depending on where you use it. walls marine life algee can affect a sonar signal realy bad. if high freq is being used say 50khz a thernal layer can suck the sig straight to the bottom. but them that me be the science of the limited range.
kws ex sub sonarman
TwistedGray
Contributor
Yeah it would work in theory; however, I imagine the range is going to be quite limited. The reason is that the acoustic receiver (transducer) is small...it has to be, it's on your wrist. My guess mirrors that of KWS in that I would expect a maximum range of about 1000ft.
Also as mentioned, you do not need a GPS underwater. You only need to get the signal from the GPS on the surface to the diver, which is what this product is doing. The only alternative would be to have a line from the diver to the GPS.
NOAA divers have used, in the past, a towed GPS. They zip-tie a GPS to a buoy and then drag the buoy above them using some rope while taking pictures of the seafloor. They can then geo-reference those pictures. It's a great idea; however, sometimes the error of the GPS can be quite high. Also, they have to take into account that the GPS might not be exactly above them...
My guess is that it is going to be priced somewhere around $1,000 because it's a two unit system (one on the boat and one with the diver). I could be wrong, but that's just a guess; anyone get a price from these guys?
Also as mentioned, you do not need a GPS underwater. You only need to get the signal from the GPS on the surface to the diver, which is what this product is doing. The only alternative would be to have a line from the diver to the GPS.
NOAA divers have used, in the past, a towed GPS. They zip-tie a GPS to a buoy and then drag the buoy above them using some rope while taking pictures of the seafloor. They can then geo-reference those pictures. It's a great idea; however, sometimes the error of the GPS can be quite high. Also, they have to take into account that the GPS might not be exactly above them...
My guess is that it is going to be priced somewhere around $1,000 because it's a two unit system (one on the boat and one with the diver). I could be wrong, but that's just a guess; anyone get a price from these guys?
I sent a message to the web site of this outfit. I asked the same questions as I did on message #10 of this thread. His answer follows:
Thank you for your interest.
Water temperature effects will not be an issue. Severe thermoclines can reduce the range somewhat, but will not prevent operation except in unusual cases.
We will add you to our mailing list and keep you informed as we near shipment.
Thank you.
- Barry
Dr. Barry Megdal
So if anybody else talks to them, I would be interested in seeing the answers you get.
Art
Thank you for your interest.
Water temperature effects will not be an issue. Severe thermoclines can reduce the range somewhat, but will not prevent operation except in unusual cases.
We will add you to our mailing list and keep you informed as we near shipment.
Thank you.
- Barry
Dr. Barry Megdal
So if anybody else talks to them, I would be interested in seeing the answers you get.
Art
I put my GPS in a pelican box, tied off my reel then dragged it above me, I then loaded the track to Google Earth and used my dive log from my watch to map the bottom by syncing the time stamps and notes on my slate and compass headings. worked great for my needs, I assume this is not why you want to know where on the earth you are underwater. my guess is that what you really need is a compass and a good bit of practice using it with drawing a map on a slate. to use a gps the same way you might lost in the woods seems a little strange to me as an underwater concept, better to stay line of sight till you can navigate using a compass and the underwater contours and signs.
Here's the last thread about the Navimate: http://www.scubaboard.com/forums/ge...ions/209714-underwater-navigation-device.html
TwistedGray
Contributor
I am not so sure how water temperature or salinity cannot have an effect on acoustics...it does unless there is some magic involved
I am not so sure how water temperature or salinity cannot have an effect on acoustics...it does unless there is some magic involved
of course these factors will affect the operation. you must keep in mind that if ray bending from refraction due to sound volicity temp salinity presure(depth)takes effect in say 1-2kyd then for all practical purposes they have no effect st < 300 yds or 1000 ft as the effect is not being realized at short range. i am sure the poster did not mean to incinuate that they have a new technology that is imune to nature. or at least i hope that is not the case. lots of neet stuff can be done with high freq, various modulations.
here would be an example of the above. data being transmitted using a fm sig tocontain the intel. a ship would not be able to use this as doppler would change the xmitted/received freq there for altering the data. this most likely would not be a concern with a diver s they sould not generate enough doppler to change the data.
if i remember right, 1/3000 is the doppler per knot so you would get 20 hz hift at 60 khz xmission per knot of opening or closing range rate. not much and is negligable if 100hz bands are used for separation of data types. so 10 cariers can be sent and all received freques will remain is the designated bands even with up to in this case 5 knots doppler. i dont know about anyone else but if i am moving 1 kt in the water diving that is pretty good clip. let alond 5 kts. which by the way most people cant run 5 kts speed. which is 6 mph or a 10 minute mile. just to keep speed in perspective.
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