Author Topic: How to locate an underwater object with a compass?  (Read 1247 times)

0 Members and 1 Guest are viewing this topic.

Offline ChrissTopic starter

  • Frequent Contributor
  • **
  • Posts: 534
  • Country: 00
How to locate an underwater object with a compass?
« on: August 20, 2020, 02:22:23 pm »
Hi!
Do somebkdy have any suggestion how can I locate the gps coordinates of an object in the water with a compass?
These objects are close to each other. Something like from 30cm to 2.5m.
From tools I have only a compass.

Thanks.
 

Online Ian.M

  • Super Contributor
  • ***
  • Posts: 13216
Re: How to locate an underwater object with a compass?
« Reply #1 on: August 20, 2020, 03:10:19 pm »
With  a *really* good magnetic hand-bearing compass, up-to-date charts and a detailed survey of any local magnetic anomalies, you could triangulate off three well spread out, distinctly visible landmarks at accurately known latitude and longitude coordinates to get a position on the surface at best accurate to approx. +/-10 meters per Km of distance from the landmarks.   You'd do better with DGPS in the boat which could reduce the surface position uncertainty by an order of magnitude or two.  Transferring that position to the seabed in anything except shallow water is problematic due to currents and tides.  In a still lake you *MIGHT* be able to maintain reasonable accuracy dropping a plumb-line.

The pros will be using something like a network of DGPS equipped sonar buoys or a towed hydrophone array with surface GPS transponders  at its head and tail.
« Last Edit: August 20, 2020, 03:12:30 pm by Ian.M »
 
The following users thanked this post: Chriss

Offline ChrissTopic starter

  • Frequent Contributor
  • **
  • Posts: 534
  • Country: 00
Re: How to locate an underwater object with a compass?
« Reply #2 on: August 20, 2020, 04:32:04 pm »
These object are in a river, around 3-6m deep.
Some wood pillars which circle are 70cm.
I shoukd as a diver go down and locate them and if any
possibility to record the coordinates.
The visibility is really poor, aroind 30cm.
 

Offline 2N3055

  • Super Contributor
  • ***
  • Posts: 7462
  • Country: hr
Re: How to locate an underwater object with a compass?
« Reply #3 on: August 20, 2020, 04:35:50 pm »
How do you expect to detect wooden (nonmagnetic) object with a compass that works on magnetic principle.... :-//
"Just hard work is not enough - it must be applied sensibly."
Dr. Richard W. Hamming
 

Offline NivagSwerdna

  • Super Contributor
  • ***
  • Posts: 2507
  • Country: gb
Re: How to locate an underwater object with a compass?
« Reply #4 on: August 20, 2020, 04:38:58 pm »
tape measure... actually two tape measures

anchor end of each at known different point... and then measure distance to each to point to be measured

plot result from triangulations

doesn't sound like a fun job in that viz

 
The following users thanked this post: Chriss

Offline Labrat101

  • Regular
  • **
  • Posts: 688
  • Country: 00
  • Renovating Old Test Equipment & Calibration ..
Re: How to locate an underwater object with a compass?
« Reply #5 on: August 20, 2020, 06:25:01 pm »
compass is useless for wood you require sonar or echo beacon . ultra sound would also work at close distance .


"   All Started With A BIG Bang!! .  .   & Magic Smoke  ".
 

Offline tggzzz

  • Super Contributor
  • ***
  • Posts: 21225
  • Country: gb
  • Numbers, not adjectives
    • Having fun doing more, with less
Re: How to locate an underwater object with a compass?
« Reply #6 on: August 20, 2020, 10:53:32 pm »
Hi!
Do somebkdy have any suggestion how can I locate the gps coordinates of an object in the water with a compass?
These objects are close to each other. Something like from 30cm to 2.5m.
From tools I have only a compass.

Thanks.

Find somebody who knows where the object is, and say "if you tell me where it is, I will give you this compass".
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less
 
The following users thanked this post: HackedFridgeMagnet, Ian.M, NivagSwerdna, 2N3055, george.b

Offline cdev

  • Super Contributor
  • ***
  • !
  • Posts: 7350
  • Country: 00
Re: How to locate an underwater object with a compass?
« Reply #7 on: August 21, 2020, 02:41:07 am »
Have a bunch of boueys that can seve the GPS locaion and attach to a bouey\\and a rope and an sold achor
"What the large print giveth, the small print taketh away."
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf