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Thread: GPS/Transducer Distance offset

  1. #1
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    Default GPS/Transducer Distance offset

    I've been thinking about this......

    I've got a 16ft boat with the structure scan mounted on the back, and the unit is mounted on the front. When I mark a pile while side scanning, and then I switch to downscan and pull up to the way point while sitting up front, am I actually 16ft in front of the pile? Or is there a setting to account for the offset distance? (my downscan ducer will be mounted on the trolling motor; I imagine I'd be trying to see the downscan but would be 16ft off mark)

    Also, this is how I'd like to set up. It's not set up yet....

  2. #2
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    Waypoints are assigned at the GPS antenna position ...

    (You didn't mention where the GPS antenna is ...is it in the head unit or is it an external antenna ...??)

    So your present GPS antenna position (in live navigating) is trying to get back to your previous GPS antenna position (when you marked it) ...

    This is why one wants the GPS antenna as close to the xducer as possible - so that the GPS position (when marking structure) is in the same place as the Sonar information (under the xducer) ...

    Rickie
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  3. #3
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    Quote Originally Posted by rnvinc View Post
    Waypoints are assigned at the GPS antenna position ...

    (You didn't mention where the GPS antenna is ...is it in the head unit or is it an external antenna ...??)

    So your present GPS antenna position (in live navigating) is trying to get back to your previous GPS antenna position (when you marked it) ...

    This is why one wants the GPS antenna as close to the xducer as possible - so that the GPS position (when marking structure) is in the same place as the Sonar information (under the xducer) ...

    Rickie
    So Rickie, would it be better to have an external antenna mounted on the back of the boat to be able to navigate back to marked way points better?

  4. #4
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    Quote Originally Posted by Ky Slab View Post
    So Rickie, would it be better to have an external antenna mounted on the back of the boat to be able to navigate back to marked way points better?
    The GPS antenna close to the xducer is beneficial in marking the structure (puts "what your xducer is seeing" closer to "what your GPS is marking") ...

    One can look at it as 2 separate functions ...:

    1. The GPS antenna is working with the satellites above it ...
    2. The xducer is working with the structure underneath it ...

    We strive to have those 2 separate functions as close to each other as possible so that those 2 separate functions meet at the same point on the Earth ...
    -----

    Returning to a Waypoint is simply the GPS antenna trying to get back to the assigned latitude/longitude (on the Earth) that was previously marked ... (and hopefully the structure that was previously found there is, in fact, there) ...

    Rickie
    Last edited by rnvinc; 08-16-2019 at 06:25 PM.
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