Tim's GPS like Sonar

Tim's GPS like Sonar

The basic idea is a hand held devices that will give position info underwater for recreational diving as well as shallow water professional diving. How it works. You have at least three sonar transmitters. These devices float on the surface and use GPS to get their position. They use wireless communications between them to provide local relative DGPS so their relative positions should be under 10 cm. Each transponder will send out a pulse about 1/4 of the time ever 1/4 second. The pattern of when they signal and when they don't is defined by a pseudo random pattern. This allows the receivers to know which transmitter was sending the timing pulse. The transmitters will also transmit other data using a modified form of Morse code. They can transmit between the 1/4 second pulses in a window that allows for a fair amount of data to be transmitted. The Sonar pulses will be in excess of 150kHz to avoid problems with confusing marine life.

The receiver works just like a GPS receiver. It determines the distance between its self and the transmitters by knowing how long it takes for the sound to travel to it. All it needs is a good time source, a good edge triggered timing circuit and the right programming to get the distances.

There are three possible market segments here. One involves one GPS receiver and two dumb buoys that are located at a fixed distance. Without the GPS component, this could still provide a high degree of navigation information.. The second market involves having a number of smart buoys that all communicate with each other using some form of radio and or sonar. This would be useful on large archaeological sites where the range may need to be extended. The last market is on large recreational dive areas. For this, the transponders are put in known locations that can be surveyed. They don

One other feature of this is that the receivers and emit a pulse and be detected by the buoys which can then fix the location and retransmit it. This would aid underwater teams in keeping their locations relative to each other or for dive masters keeping track of recreational divers.

One other feature of this system is for position along underwater caves. One one transmitters needed and the receiver can just display the relative distance from the transponder and the direction of travel.

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