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  1. Member
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    Sep 2007
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    Georgetown, TX
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    760
    #21
    Trust Tommy-he knows his stuff!

  2. Member
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    Mar 2016
    Location
    Missouri
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    47
    #22
    I wish this site was more friendlier to video uploads and links. You type a complete soliloquy, just to have it lose it all with an erroneous "server error".
    My apologies for not getting out this evening, I was forced to run by the office for a matter that needed my attention. Fishing is just a hobby, a guy needs a few pesos to pay the bills that's where my attention must be prioritized.

  3. Member
    Join Date
    Mar 2016
    Location
    Missouri
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    47
    #23
    Hey guys,
    Finally was able to get on the water this evening and try to solve the puzzle. It's important to know that I don't have a bass boat so my particular setup is unique. I do have a few 12s and a point one antenna

    I don't know appropriate way to do this because I'm scared deathly ill have a for page write up and the server error deletes it all. So I'll just proceed in steps.

    Abstract: We are looking to find out if there is a transducer offset to account for when marking Waypoints accurately. We would also like to know if this but offset is applicable to the trackback feature.We may find other instances that cause inaccurate Waypoint marking along our journey.

    Volume I. Equipment

    As I stated earlier, I have 2 HDS 12s gen 3 models with a point one. My forward helm boat causes my internal antennas from my MFDs to be 19 feet from my transducer mounting location.
    Below is our first illustration of differences in equipment, according to lowrance standards.
    rps20170719_175554_935.jpg

    On the left, I have unplugged the point 1 antenna, and the details are listed below. The HDS on the right is running the Point1 as it's source.

    EPE- Estimated Position Error is a proprietary formula developed most likely be lowrance that has a pre-assigned confidence interval that our true position is inside a spherical error margin listed in ft. To simple men like me, basically what this is telling me is that my position is more or less accurate within this margin of error. It is more complex I'm afraid as we are accounting for substantial vertical error, which in all reality, we don't really care about- thus our horizontal error although there's deviation with the point 1 it's very close, as for our internal- I would say our horizontal error is somewhat substantial.

    Notice as well the differences in longitude/latitude, the points differ. As said before, different placement of antennas is most likely the cause of the deviation. We can jump into that shortly, but it's worth mentioning.

  4. Member
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    Mar 2016
    Location
    Missouri
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    47
    #24
    Volume II Static Test

    As we saw above there is deviation I'm longitude and latitude. Because lowrance does their GPS in meter mercator usually this number can only move in 3 ft+/- increments. So is the number trivial, that's all were after.

    Simply to know, we could do several static instances with the boat parked, with the setup from above ( one internal at the helm, one external Point1 at the transducer) and find an average over three instances. All I'm doing is hitting the mark button on both units at the exact same time, and selecting the exact same icon. Waypoints followed by a "B" will be internal at the helm antenna, Waypoints followed by an "A" will be the Point1 at the transducer.rps20170719_182112_286.jpg

    Pardon me for not getting pictures of all but +/-20ft was average

  5. Member
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    Mar 2016
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    Missouri
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    47
    #25
    Volume III Moving Test

    I did my best to perform this test by idling over a decernable piece of structure shown.rps20170719_185822_985.jpg

    I only marked the structure using down scan- Not left/right structure scan. I placed the cursor on the screen in the same spot for both the left and right unit (Point1 vs internal), and marked the structure. Again, an "A" is point 1 at the transducer, a "B" is there internal at the helm. Due to the placement of the structure I could only go from North to south or south to North.
    Pictured below is the coordinates marked on the varying antenna locations.rps20170719_191206_217.jpg

    Again, were worried about Downscan only.rps20170719_190253_104.jpg

    As you can tell going north the mark of B was off to the north, going south the mark of B was off to the South. A marks however were extremely close to the same locale.

    Anyone looking at this is forced to take it with a grain of salt, quite a few moving pieces here. But even with an outlier , I think the point can be made the static discrepancy we saw in Volume 2 carries through in this test, which makes sense that trackback is unfortunately victim to the same discrepancy.
    Last edited by cgesling; 07-19-2017 at 07:12 PM.

  6. Member
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    Mar 2016
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    Missouri
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    47
    #26
    Volume IV Structurescan and Slant range
    I suppose while we are here it's necessary to mention the inaccuracy of legacy sidescan as related to slant range.

    What this means is if we mark a target off to the side of our 2D structurescan we are subject to errors due to the water column getting a identified with varying longitude and latitude points it should not obtain.

    With structure scan 3D this is easily depicted...rps20170719_192536_445.jpg

    Here we have marked a concrete slab, but not of gigantic proportions, we've marked it with both 3D and 2D sidescan. One could assume that the Waypoints should be the same long/lat. But don't be fooled.

    When we go to our chart, this is what we see..rps20170719_193102_704.jpg

    A deviation of near 13 ft. (Note: this was done on the same MFD, no difference in GPS source).

    This deviates more in deeper water, as the water column is assigned a lat/long when nothing changes but elevation, or as you get closer to your boat, due to the geometry- the further you mark away from your boat- technically the more accurate you will be.

    Those with Gen2 units or lss2 transducers can prove this as well by using structure map overlay- a deviation will still be excessively present.

    Every sonar manufacture is subject to slant range, as no one has bottom tracking features that know depth of water column and do not account/assign it a long./lat point.


    Enough with the jargon. I believe it's time to throw a few poles out. Have a good evening fellas.
    Last edited by cgesling; 07-19-2017 at 07:46 PM.

  7. Member
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    Jul 2014
    Location
    Richmond Va
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    667
    #27
    Wow. This is far and away a way more in-depth answer than i could have hoped for. I'm surprised to learn about the lack of accuracy marking structure to the side. I would assume that the same offset will be present when i bring the tracks into Reefmaster. Guess I'll be spending more time confirming with downscan...

    Thanks again to everyone!
    2019 Ranger Z520C
    2019 Mercury 250 ProXS 4S
    Twin 8' Powerpole Blades
    Lowrance HDS Live 12
    Lowrance HDS Live 9

  8. Member
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    Mar 2016
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    Missouri
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    47
    #28
    Reefmaster has the ability to apply a latency or advance in your long/lat because it has an option to put the offsets from your unit to your xducer in the program. It also contains a bottom tracking algorithm if you will and removed your water column and adjusts the lat long accordingly. Matt has done a super job with that program. The clarity, bottom smoothing and filtering options on SL3 files is phenomenal.

  9. Member
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    Oct 2010
    Location
    Fort Worth, TX
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    #29
    cgesling,

    Thanks for taking the all time and effort required in investigating and presenting your findings regarding this question, much appreciated! You have presented a ton of data for everyone to review and come to their own conclusions.

  10. Member
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    Apr 2012
    Location
    TN
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    170
    #30
    The whole data info stated is likely wrong. IF the transducer is installed inside, in the bilge, there is an error already in the beginning of the calculations. With the boat stationery, does it look straight down to mark a spot, or is it off a little, THAT is an unknown variable...then what i teach in ALL of my seminars is the extreme error in locating a spot...When it is assumed that what you see on your sonar screen is directly under the transducer...which I believe is the mistake here...Then when the boat moves forward even at idle..that stationery transducer in the bilge at the transom ,when the transom tucks down lower as the bow rise goes up..then that transducer is likely to be seeing 20-30' more or less feet forward of what you think is straight down. IT IS NOT SEEING DIRECTLY UNDER THE TRANSDUCER.
    I do this for classes on a whiteboard and when the students see it...they get it. Which is THE reason even when they throw back a marker buoy based on what is "they assume" "directly under", then circle back and cannot find it...because it was NOT directly under the transom when they threw the buoy...This also accounts for the discrepancies based on water depth. Deeper water then the ducer would see even further out in front typically. Likely the whole thing is flawed due to transducer placement and the lack of ability to adjust it for bow rise etc. Even the High School fishing clubs I teach, they can see it on the white board and get it. Flawed information in ...flawed results out..based on a false assumption of transducer/mark spot waypoint accuracy. Without that known dependable basis..if that is even a little off, tilted any small amount in any direction....every assumption from there forward goes right out the window. Just common sense when you think about it in simple terms...
    Tommy
    Prostaff Lowrance/Navico
    Prostaff Marine Specialist/Navico

  11. Member
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    Mar 2016
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    Missouri
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    #31
    I concur with you 100%. Similar to ledge fishing in 2D, without making a zig zag pattern to the top of the ledge and back down you are missing over half the data desire simply because that track you are making with a cardioid cone manipulates bottom tracking depending on your frequency.

    No doubt it's super impressive technology, but being aware of the caveats of viewing a 3D world in 2D perspective, or viewing a 3 dimensional cone in a 2 Dimensional, will make you a better. Just know the capability of your electronics. They are extremely extremely useful when used correctly- or they can be most overly fustrating when the understanding is poor.

  12. Member
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    Mar 2016
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    Missouri
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    #32
    And Tommy I just wanted to say I feel comfortable with the resolve here. As mentioned before I touted no ill-will. I work several hours and my blood pressure is plenty high enough majority of the day I definitely don't go out of my way to ruin someone else's day or create stress- especially stemming from an completely inmaterial message board I only became a part of to learn of a hobby more in depth. Just wanted to say I appreciate your response, and look forward to many many more fruitful informational topics and responses.

  13. Member
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    Mar 2016
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    #33
    Mak747-

    I appreciate the recognition. To be truthful- I enjoy learning the basis and platform of the sonar technology as much as I enjoy fishing. Good luck to you!

  14. Member
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    Aug 2009
    Location
    Fresno
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    101
    #34
    I'd like to attack this from a slightly different 'angle', pun intended. If we can limit this, (or my comments), to structure, almost 100% of the time when a boater marks a waypoint he is already way off that structure. We all know when structure appears on your screen, it is for all intensive purposes, history, as you view it. The advantage to using 'TrackBack' when marking your waypoint IS your ability to be much more accurate by placing the cursor exactly on the structure, (or, exactly above the structure). Using DownImaging or 2D sonar to mark a piece of structure, already has you at a location disadvantage simply due to the means by which the MFD gets the data to draw. A round search area! Let's forget about marking and think more about 'returning' to a waypoint. When you pull up to any waypoint you have no way of knowing if you need to cast your bait left, right, for or aft of where you are. If you use StructureScan to not only mark your structure, but also to return to your structure, you have a distinct advantage of knowing which side of the boat your point is located. And if you want even more accuracy you can use a 2 waypoint system.

    All this talk about GPS accuracy of 'mark to structure' is ludicrous. After all you aren't driving to the structure, you're driving to a point ABOVE the structure. After you get there, you know the depth. Like I said earlier, you're driving to a spot above the structure, so, why is it relevant to bring any sort of angle correction/allowance into marking your waypoint? Also, your wallets and our Government keep us from equipment that would render real accuracy.

    At my seminars I always ask my audience; "How many of you here tonight have EVER caught a fish without having a sonar or gps?". Let's use this equipment for the advantages it offers us, and not as a platform for argument.

    Edd

  15. Member
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    Mar 2016
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    Missouri
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    #35
    I'm sort of following you Edd. I have a tendency to agree with you, that we are driving to an (x,y) coordinate not an (x,y,z) coordinate.
    I think the habit to mentioned is a great one ( two waypoint system). In scenarios where you are marking large structure, a big underwater road bed, bridge, or brushpile it's a great habit to not only mark that structure in center- but mark it several times on the edges. Such that you can see the outline of your structure via waypoints on your chart screen.

    In instance of a brushpile- mark it on all four sides. If you've got an extremely ledged point, mark it several times so you can see the point on your chart though the waypoint icons.

    If your into more effort, more accuracy, log sonar over that area. Purchase a reef master ( or similar software) create a structure scan mosiac that you can lay over your chart and see your orientation and position to the structure. It all depends on what you fish for, how you fish, how your equipment is set up, and just how active that fish is.

  16. Member
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    Apr 2012
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    TN
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    #36
    Speaking of equipment, what units are you using, which transducer and how is that mounted, bilge, transom ??
    Tommy
    Prostaff Lowrance/Navico
    Prostaff Marine Specialist/Navionics

  17. Member
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    Mar 2016
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    Missouri
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    #37
    I'm not sure if you were inquiring about my gear or not but I run 2 HDS Gen 3 12s at the helm, my 2D is transom mounted below the point one antenna, it's the HST-WSBL on 200, as I just found out through BBC high chirp causes SS interference (should have read the manual). I then run the 3D for my sidescan transducer. I have an Xi5 with PinpointGPS but I don't use the 2D xducer capability of it.

  18. Member
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    Apr 2012
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    TN
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    #38
    Cool, Nice setup. Just was curious....how do you like and have you totally evaluated your XI5/pinpoint?? And have you linked it to the HDS system with good results. How steady is the pinpoint.
    Tommy
    Prostaff Lowrance/Navico
    Prostaff Marine Specialist/Navionics

  19. Member
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    Mar 2016
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    Missouri
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    #39
    I have. And for good comparison I had a Minn Kota Terrova 112# thrust with ipilot link. The motorguide xi5 is the 105# model. Spot lock is the most noticeable difference. Absolutely , unequivocally, better with the pimpin GPS. There is a compass calibration in the Xi5 I really like that so it doesn't wrap the cord around itself no matter the orientation it's mounted.

    Granted, I've heard- but not witnessed, the improved spotlock ability of the ulterex. Motorguide couldn't re-market their feature like Minn Kota quite simply because it's near flawless.

    I still believe there is more thrust in the 112 vs the 105, I really didn't believe I'd notice 7# difference, but I do.

    Is their anything in particular you want me to review about it? I've been very impressed with it, the design, components, the integration, intuitive function. It's a great unit.

  20. Member
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    Oct 2010
    Location
    Fort Worth, TX
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    #40
    Hi cgesling,

    It seems that most on here run some type of bass style boat but I see that your rig is a forward helm North River, is that a Seahawk series? I checked out their website and they look to be rather impressive boats. Just curious as to what type of fish you normally target.
    Last edited by mak747; 07-22-2017 at 09:52 AM.

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