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View Full Version : Reality or utopia? Underwater "gps"


Gerard Peels
26-05-2008, 19:13
Dear all

As the majority of us is familiar with positioning systems like gps and inertial systems (gyros) or combinations of these in addition to other sensors, is it that much of an illusion to have submerged "beacons" transmitting their own "code" for their (maybe encrypted) location and depth?

Being not at all familiar with any modern electronical submarine equipment in this field, I can assume that receiving these identifyable transmitted signals allow for triangulation and subsequent determination of a subs position.

Question: is this meanwhile reality or just bogus?

Brgds

Gerard

Gerard Peels
17-02-2009, 19:35
Dear All

Although being not liaised with any navy, I was able to get the question answered:-

Source: http://appft1.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PG01&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.html&r=1&f=G&l=50&s1=%2220070025185%22.PGNR.&OS=DN/20070025185&RS=DN/20070025185

Here it is mentioned and explained how it works:

Underwater geopositioning methods and apparatus

Abstract

A method and apparatus for determining the geophysical position of an autonomous underwater system utilizing underwater acoustic modems that exchange broadband underwater acoustic signals. The method of the invention includes the steps of initiating an exchange of broadband acoustic signals between the autonomous system of unknown geophysical position and a base system of known geophysical position wherein the depths of both systems is known. A bearing calculation is made on one of the signals transmitted between the systems, preferably through the use of an array of hydrophones placed closely together at predetermined locations on either the autonomous or base system. Also, the range between the two systems is determined by measuring the time of travel of at least one signal. By the acoustic transmission and sharing of information, as needed, about the known depths of the systems, the known geophysical position of the base system, and the range between the systems, sufficient data is gathered at one or both systems and used to determine the geophysical position of the autonomous system.
Inventors:Green; Maurice D.; (North Falmouth, MA) ; Scussel; Kenneth F.; (East Falmouth, MA)

I knew it was simple.....for the maths, trigonometry, and geodesics see details mentioned at the web site. Sub meter accuracy over thousand of kilometers distance from transmitter and receiver......just one "ping"??

Francis Stanley
18-02-2009, 11:02
Dear all

As the majority of us is familiar with positioning systems like gps and inertial systems (gyros) or combinations of these in addition to other sensors, is it that much of an illusion to have submerged "beacons" transmitting their own "code" for their (maybe encrypted) location and depth?

Being not at all familiar with any modern electronical submarine equipment in this field, I can assume that receiving these identifyable transmitted signals allow for triangulation and subsequent determination of a subs position.

Question: is this meanwhile reality or just bogus?

Brgds

Gerard



Gerard
There are diver systems under development that employ the use of positioning systems from previously laid beacons that will tell the user where they are within a designated grid that can be tied into lat and long, there are also ways of using hand held gps systems underwater but they usually only work in shallow waters (less than 10m) and require an arial on the surface.

Vessels that need to know where they are exactly (off shore exploration for example) can also deploy beacons into an area and use them for positioning them

Gerard Peels
18-02-2009, 20:46
Dear Mr Stanley

Taking reference to your quote:-
"......there are also ways of using hand held gps systems underwater but they usually only work in shallow waters (less than 10m) and require an arial on the surface."

I was aware of even an American brand providing that equipment to the military, but as it seems now, the product is not available anymore....
Shame as it would have been an effective instrument for e.g underwater archeology,etc.

Besides, to my understanding, the antenna did not even have to reach the surface as 1 meter below was enough for the satellite signals (GPS) to pass.

This then would work regardless of "working" in shallow or "deep" waters.

The original question was about a positioning system reverse to what we all know as GPS. The satellites flying around the earth in an orbital elevation are not geo-stationary, needs no further explanation.
The "reversed underwater system" would use beacons as you mentioned your self, pre-set to a exact known position, however statically used.
As described these beacons could be many thousand kilometers apart, and, as one can reads, bare and bold physics, maths, trigonometry and geodesics would then eventually and supposingly lead to a underwater position within 1 m accurate.

Having worked myself with GPS for some years, at certain times and locations up to 9 satellites could be used to determine the position (simplified). One should bear in mind that there is by using GPS hardly any interference of other media, such that one's GPS device would not measure "bounced back, distorted signals" (again simplified). This, on the other hand, is not clear to me how it would work underwater for two reasons:-
1) underwater apparently sound is used, transmitted
2) underwater occur inevitably other physical and physilogical impacting parameters causing a indirect and distorted recording of the sound transmitted, which subsequently would decrease accuracy

I think I would have to try it before believing it....