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  1. #1
    Member
    Join Date
    May 2016
    Location
    Hopatcong, New Jersey
    Posts
    934

    Side imaging and waypoints

    I have a new helix 10 and Ipilot terrova. I've never used or even observed side imaging before and wondered how useful it might be.
    The image clarity and detail are amazing. I have little experience so far, but using default side image settings, I have dropped waypoints on some rock formations in 20 - 25 feet of water at various distances from the boat. Using the Ipilot "go to waypoint", the terrova takes me to the rock formations which I can see on 2D and down imaging.
    My question concerns the the accuracy of the waypoint. I have been freezing the screen and dropping the waypoint on top of the object. That has worked very well. But I understand that the range shown is the direct range to the object on the bottom, not the horizontal range. Does the helix software do some calculations to estimate the horizontal range to increase the accuracy of the waypoint based on the depth under the boat ? Should I develop a feel for dropping waypoints slightly closer to the boat than the desired object based on depth ?

  2. Member
    Join Date
    Jul 2018
    Location
    Lower Burrell Pa
    Posts
    1,643
    #2
    if your " go to waypoint" is taking you right over it that you can see on 2d or downscan then id say what youre doing now is working.

  3. Member
    Join Date
    Nov 2017
    Location
    Sellersburg, IN
    Posts
    1,747
    #3
    following

  4. Member
    Join Date
    Jul 2010
    Location
    Big Sandy, TX
    Posts
    643
    #4
    Unless HB has changed their GPS algorithms, they triangulate the distance on waypoints. So the distance is horizontal from the GPS location of the boat's GPS antenna.

    This would be very accurate if the lake bottom is flat. Error is introduced if the lake bottom were angled. More slope, more error.

    Lowrance use slant-range for distance. Slant-range is the direct line distance to the object.

    Keep in mind your GPS EPE(estimated position error) is another factor. EPE can change throughout the day.
    Last edited by LittleGazoo; 09-29-2019 at 07:26 PM.