Connect with us

Regarding Depth Calculation

Discussion in 'General Electronics Discussion' started by naseer39, Dec 28, 2011.

  1. naseer39

    naseer39

    11
    0
    Dec 28, 2011
    Hi to everyone..

    I am using a IMU triaxial sensor from MEMsense which gives Accelerometer,Magnetometer and Gyroscope data.I have calculated Pitch,roll and Heading.Now i need to calculate Depth, can any one help me out ??????????

    Thanks in advance,
    S.Naseer:)
     
  2. OLIVE2222

    OLIVE2222

    690
    25
    Oct 2, 2011
    Hi naseer39,

    Welcome to this forum !
    Already having calculated Pitch,roll and Heading do you feel that any of the IMU sensors is
    able to help you in the deepth calculation ?

    Olivier
     
    Last edited: Dec 28, 2011
  3. naseer39

    naseer39

    11
    0
    Dec 28, 2011
    Hi,

    I have contacted Memsense but no reply from them.............:(

    Regards,
    S.Naseer
     
  4. OLIVE2222

    OLIVE2222

    690
    25
    Oct 2, 2011
    Hi,

    My question was not linked to any IMU manufacturer. With any type of accelerometer,magnetometer and gyroscope do you feel that you can calculate the depth ?
    What the final project will be? A model submarine?

    Olivier
     
  5. naseer39

    naseer39

    11
    0
    Dec 28, 2011
    Hi,

    We are working on Borhole survey system . We need to calculate depth(distance) it
    has travelled into the borehole.I also need a clarification whether we can calculate
    depth(distance) by using these parameters.????

    Naseer
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,214
    2,695
    Jan 21, 2010
    Don't you lower this thing on a cable? Don't you take readings every certain distance down the hole?

    Either a direct reading of the length of cable (which will give you the length of the hole) or that combined with the normal 3D maths you're presumably already doing to get the position in space of each point down the hole.
     
  7. naseer39

    naseer39

    11
    0
    Dec 28, 2011
    Hi Steve,

    We are using cable for lowering our thing,but is it possible to calculate distance with Accelerometer and Gyroscope readings with out the reference of cable ???

    Naseer
     
  8. naseer39

    naseer39

    11
    0
    Dec 28, 2011
    Hi steve,

    One more thing i forgot to tell that we are using a Winch to drop our thing in the borehole..

    Naseer
     
  9. OLIVE2222

    OLIVE2222

    690
    25
    Oct 2, 2011
    Hi,

    Sorry for the post bouncing, just want to find out if it was a homework. The IMU platform will only provide you attitude indications. To measure the depth you can use (a well calibrated) pressure sensor, maybe a ultrasound, radar or laser ranging equipment. This to have it independent.

    Olivier
     
  10. naseer39

    naseer39

    11
    0
    Dec 28, 2011
    Hi Olive2222,

    So,it is not possible to calculate depth(distance) with IMU sensor.....Thanks for the information....:)

    Naseer
     
  11. OLIVE2222

    OLIVE2222

    690
    25
    Oct 2, 2011
    Hi,

    You welcome Naseer ! No, nor the depth, the distance, or the altitude.
    Maybe having accelerations in known (or measured) time can act as depth indication, not a real measure however.

    Olivier

    EDIT:

    Well you talk about survey not drilling, so maybe you can characterize the winch resistance and let the IMU fall till hitting the ground. Combined with the time you should be able to have reasonable precision.
     
    Last edited: Dec 29, 2011
  12. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,214
    2,695
    Jan 21, 2010
    Well, in theory, a gyroscope and accelerometers form the basis of an inertial navigation system.

    However, practically, it it may be difficult to resolve the small accelerations which take place as the probe moves down the hole with sufficient accuracy to determine depth.
     
  13. daddles

    daddles

    443
    3
    Jun 10, 2011
    You don't give any details about the accelerometer, but you say it's a three-axis device. Theoretically, you can integrate the acceleration data twice to get the displacement (see any freshman physics book). However, I'd imagine the results could contain significant errors over time unless you have good accelerometers. You can easily do some simulations with some computer programs to see how things might work.

    But if you're lowering it on a cable, it seems to me that the simplest solution is to measure how much cable has gone out and correct for the stretch caused by the load and cable mass. No doubt there are many tens of commercial things that do this already on the market.
     
  14. naseer39

    naseer39

    11
    0
    Dec 28, 2011
    Hi ,

    i need a small clarification i am getting values of acceleration in "g",can we calculate speed from the acceleration.I know the basic formula V=A*t but where can i get "t" from???
    can u please help me out???????

    Naseer
     
  15. Laplace

    Laplace

    1,252
    184
    Apr 4, 2010
    The basic formula given is for a constant acceleration, and the "t" is for the duration of the acceleration. However, your package is unlikely to be subject to constant acceleration during its movement. In that case you need to integrate the A(t) function over the total duration with respect to the differential time in order to find V(t).
     
  16. naseer39

    naseer39

    11
    0
    Dec 28, 2011
    Hi Laplace,

    Practically we dont have uniform time,then integration can give accurate readings?

    Naseer
     
  17. Laplace

    Laplace

    1,252
    184
    Apr 4, 2010
    Non-uniform sampling times are just another potential source of error that must be dealt with, along with sensor error and instrumentation offsets. You would need to manage the error budget carefully, since performing a double integration can magnify small errors into much larger error.
     
  18. naseer39

    naseer39

    11
    0
    Dec 28, 2011
    Hi,

    Can we calculate Heading direction of IMU Sensor travelling downwards? i have calculated Heading for object travelling horizontal(NED convention)by using Accelerometer and Magnetometer.It is working fine...I am unable to findout in Vertical Case..can any one help me out?????

    Thanks,
    Naseer
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-