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  1. #1
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    Default The MNemo - a review

    Attached are our results from the weekend.

    TL;DR - it didn't go well.

    (Apologize for the repost it got moved and disappeared.)

    Click image for larger version

Name:	Surveying with the MNemo.pdf
Views:	401
Size:	1.54 MB
ID:	16591


  2. #2

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    Thanks for the extensive write up Jason. A little disappointing to hear. Looks like I will stick with counting knots until version 2 comes out.

    Michael Thornton
    CCR Cave Instructor (TDI / IANTD)
    CCR Instructor (TDI / IANTD)
    www.CCRMichael.com
    www.DiveAddicts.com - Online Store
    TEKDiveUSA.2014 - The North American two day advanced and technical diving conference.
    Miami, FL - May 17-18, 2014

  3. #3

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    Jason,

    Great review. Thanks. I have some comments:

    1. Calibration

    I had to email Sebastien Kister to ask about the calibration. He pointed me to a video showing how to do it:

    https://1drv.ms/v/s!AmU_dbFt4gU3iLY7ohdrip9XXvaSLA

    The numeral after the colon is a rough indicator of how 'good' the calibration is 0,1 or 2. From Sebastien:

    "It is a "quality" of calibration achieved so far, usually you'll only see 0 or 1 rarely 2. It might go down again from 1 to 0 especially if there are interferences."

    He stressed it's very important to avoid magnetic interference during calibration. Even a watch on the arm moving the unit can affect it. As the battery lasts for 8 hours my plan is to calibrate it as I get in the water and then leave it switched on until I need it. I don't want to be spending 10 minutes at 300 feet trying to get it to calibrate!

    2. I found that it only increments the distance in the direction of the arrow, so you can add distance by backing it up the line and running it forward again. This can compensate for short pieces of line that you skip over, like line arrows and big knots. You don't need to create a separate station for these; just take the line out of the gate, move to the other side and put it back in. It doesn't end the shot until you tell it to.

    3. I think the reference shots at the beginning of each section denote the shot before and after the station that the section ties into. I personally wouldn't bother with the length of these most of the time - in my experience 2 azimuths is enough to identify the tie-in station on most occasions. I agree that it would be great to be able to identify the tie-in point of a T during the main line survey, but it would complicate the user interface.

    I think the Mnemo's real value will be for those occasions where you need to survey unknotted line left by some inconsiderate person and tape is impractical. With a digital compass like the H3 (did you calibrate yours just before you used it - even temperature changes will affect the calibration?) and practice it is possible to survey knotted line very quickly indeed.

    We should feed all these issues back to Sebastien and hopefully version 2 will address them, or maybe even a firmware update.

    Andy


  4. #4

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    Quote Originally Posted by rchrds View Post
    Attached are our results from the weekend.

    TL;DR - it didn't go well.

    (Apologize for the repost it got moved and disappeared.)

    Attachment 16591
    ?? I get a broken link, same as in other thread.
    Looking forward to reading it.

    Thanks, - Jeff

    Sent from my SM-T810 using Tapatalk

    Jeff Rouse
    Chicago, IL

  5. #5
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    Default

    Quote Originally Posted by apitkin View Post

    1. Calibration

    The numeral after the colon is a rough indicator of how 'good' the calibration is 0,1 or

    "It is a "quality" of calibration achieved so far, usually you'll only see 0 or 1 rarely 2. It might go down again from 1 to 0 especially if there are interferences."
    That makes sense, I actually saw the number drop from 1 back to zero on one occasion, then eventually back to one. This makes much more sense than what we were surmising. The link will be helpful to everyone else!
    Quote Originally Posted by apitkin View Post

    2. I found that it only increments the distance in the direction of the arrow, so you can add distance by backing it up the line and running it forward again. This can compensate for short pieces of line that you skip over, like line arrows and big knots.
    That is a good fix, we didn't notice this feature, as we were intent on trying to get the most accurate forward measurements possible. You would have to re-roll the length of the obstacle plus the length of the device as you would lose half a device length on either side, not difficult to do.

    Quote Originally Posted by apitkin View Post
    3. I think the reference shots at the beginning of each section denote the shot before and after the station that the section ties into. I personally wouldn't bother with the length of these most of the time - in my experience 2 azimuths is enough to identify the tie-in station on most occasions. I agree that it would be great to be able to identify the tie-in point of a T during the main line survey, but it would complicate the user interface.
    I omitted this in my review, as we couldn't figure the purpose of the reference shots, but I think you are right, they are likely as you described. This would work in really curvy passage, but it might still be confusing in a straight section. I'm still leaning towards a note card on the back of the device to jot quick notes like that.

    Quote Originally Posted by apitkin View Post
    I think the Mnemo's real value will be for those occasions where you need to survey unknotted line left by some inconsiderate person and tape is impractical. With a digital compass like the H3 (did you calibrate yours just before you used it - even temperature changes will affect the calibration?) and practice it is possible to survey knotted line very quickly indeed.
    I agree. We did calibrate the H3, I thought it's numbers were pretty good for a device that likely has the same compass chip. Most digital compasses do not have the accuracy they advertise, despite having a decimal resolution, unfortunately. The only exception I have seen less than a few thousand dollars is the Disto X2, and it requires a significantly complex calibration routine.

    Quote Originally Posted by apitkin View Post
    We should feed all these issues back to Sebastien and hopefully version 2 will address them, or maybe even a firmware update.
    Andy
    I hope he will take them well. I also believe the clamp could have a rounded arc that is tightest around the wheel, so things coming into the groove will gradually open the clamp, rather than bumping around the corners. Someone else had already fixed the spring issue above, so we are making progress. I'm sure machining decisions were made to keep costs down, but I would pay more to see the simple operation demonstrated in the prototype videos.


    Sent from my iPad using Tapatalk


  6. #6
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    Default

    Jeff, the link wont open in tapatalk, you may have to find a desktop to read it.


  7. #7

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    Quote Originally Posted by rchrds View Post
    Jeff, the link wont open in tapatalk, you may have to find a desktop to read it.
    Ok, Thanks Jason.

    - Jeff

    Sent from my SM-T810 using Tapatalk

    Jeff Rouse
    Chicago, IL

  8. #8
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    Default

    Now that I have watched the compass calibration video, I am sure we didn't give the MNemo a fair break, considering we didn't do a proper compass calibration. Also, it is best to set up a test line course in the daytime, and do a practice survey after dark. That is because you get a "Too much light" error if the sun overpowers the wheel sensors.

    Forrest Wilson (with 2 Rs)
    Any opinions are personal.
    Sump Divers

  9. #9

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    Quote Originally Posted by FW View Post
    Now that I have watched the compass calibration video, I am sure we didn't give the MNemo a fair break, considering we didn't do a proper compass calibration. Also, it is best to set up a test line course in the daytime, and do a practice survey after dark. That is because you get a "Too much light" error if the sun overpowers the wheel sensors.
    Would a bright canister light cause issues as well?


    Sent from my iPhone using Tapatalk

    Michael Thornton
    CCR Cave Instructor (TDI / IANTD)
    CCR Instructor (TDI / IANTD)
    www.CCRMichael.com
    www.DiveAddicts.com - Online Store
    TEKDiveUSA.2014 - The North American two day advanced and technical diving conference.
    Miami, FL - May 17-18, 2014

  10. #10
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    Default

    Quote Originally Posted by CCRMichael View Post
    Would a bright canister light cause issues as well?
    Probably, if you let it shine directly on the display, but there is no need, the display is back lighted.

    Forrest Wilson (with 2 Rs)
    Any opinions are personal.
    Sump Divers


 

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