Lowerance waypoints

[watespeyton]

I've loved my Lowerance HDS gen 2 and it's structure scan features but I have notice a problem while marking off shore structure. I will mark fish, a brush pile, etc on my screen as I see it on side imaging or downscan and fish that exact waypoint. I've noticed after marking the waypoint especially on side imaging that when I drive over the spot that I marked previously the brush or structure is not as I saw it before. I am starting to question the accuracy of the waypoints when they are used in the structure scan feature. Does anyone know how I could fix this or having the same problem?

[Wayne P.]

The accuracy is based on the GPS accuracy at the time you create a waypoint and the accuracy of GPS when you return to a waypoint. Additionally when you mark a waypoint based on sonar returns, the location is in relation to GPS antenna. If the antenna is not where the transducer is, you will have created a position error of the distance between the antenna and transducer.

If you return to the waypoint from the same direction as created, the error will be the same. If you return to the waypoint from the opposite direction, the error will be double.

For a console mounted display, an external GPS antenna at the transom will give you better waypoint accuracy.

You can check the GPS accuracy with the GPS diagnostic view. This is a HDS with remote antenna connected:

 

 

[WIGuide]

Something else you might want to check out is the orientation of your transducer. Since the structure scan transducer is rather large, Lowrance put in an option to run a flipped image on the screen for structure scan in the event it works better to install your transducer backwards. It's worth checking to make sure that is set up correctly since if it's not you'll be dropping waypoints on something that looks like it's on the right side of the boat when it's actually on the left. Easiest way to check is to idle past something that sticks out of the water so you know it's there (bridge piling, docks that have posts, even a shoreline) Verify that it is displaying on the correct side of the boat as you idle past it. If not correct it and then try again. 

[tkunk]

I have gen 3 Lowrances, and I've noticed the same issue as the OP. I'll mark an isolated boulder or crib in ~20 fow on side imaging, but when I try to find it using down imaging, it's often not where the mark is (but it's usually pretty close). I figured the issue was that waves/wind were messing with my speed and position, which would prevent the system from providing an accurate estimate of the boulder's position relative to the transducer when I made the mark.  I've found that marking stuff on calm days while moving in a constant speed in a straight line helps quite a bit.

With an antenna, is it realistic to expect to be able to mark a boulder on side imaging and be able drive over it on down imaging?

[gulfcaptain]

I installed my Lowrance Point 1 antenna next to my console(all units run off this atenna for a common position and location center of the boat) as so when I'm looking I know the mark I put will be right were I'm sitting which will put the piece I'm looking for 6ft away from the waypoint.  Now you also have to know which way you were traveling as so you can get a bering on the structure or whatever you dropped the waypoint on as so you can line it up and drive over it.  I also use a bow unit with it's own transducer and unit to mark the bottom and have a seperate unit for my chart next to it.  I know if I mark waypoints on the bow then when I run over the top of it with the chartplotter from up there when I get on top of it the item should be under the bow.  Different marks for each as so I know where I'm marking.  And if I have a big brush pile or rockpile on side scan, well I try to drop waypoints around the structure or cover so it's in the middle of the waypoints as so I can back off and cast into the center of them and know I'm pretty darn close to where I want to be.

[WRB]

You also need to take into account the image is history as it gets displayed, you have already passed it if moving forward. Circle around and make another pass following your dead wake watching the far right side digital display that indicates the structure/fish before the image appears across the screen and make the way point. At idling speed you are moving about a boat length every few seconds, that's about how far off the screen display can be coupled with GPS antenna location.

Tom

[Wayne P.]

WRB, the units I have will create a waypoint from the history on the screen very accurately---have done dozens.

Assisted with a SAR operation and marked a "target" on the screen history, then lead the dive team directly to it.

Not only that I can play a sonar log on my computer with HumViewer software and determine an accurate waypoint on the Side Imaging view to load to all my units. Can do the same by playing back sonar logs in the unit itself in my den to create accurate waypoints.

The Lowance should do the same with Side Scan, as well as Garmin and Raymarine.

GPS antenna proximity to the transducer is the only error there should be.

[WRB]

I agree if that is what the OP is doing, using Lat/lon target points as way points with a cursor. If you use a scrolling target as a real time target, then it may not be accurate.

Tom

[WIGuide]

On 12/14/2016 at 1:17 PM, gulfcaptain said:

I installed my Lowrance Point 1 antenna next to my console(all units run off this atenna for a common position and location center of the boat) as so when I'm looking I know the mark I put will be right were I'm sitting which will put the piece I'm looking for 6ft away from the waypoint.  Now you also have to know which way you were traveling as so you can get a bering on the structure or whatever you dropped the waypoint on as so you can line it up and drive over it.  I also use a bow unit with it's own transducer and unit to mark the bottom and have a seperate unit for my chart next to it.  I know if I mark waypoints on the bow then when I run over the top of it with the chartplotter from up there when I get on top of it the item should be under the bow.  Different marks for each as so I know where I'm marking.  And if I have a big brush pile or rockpile on side scan, well I try to drop waypoints around the structure or cover so it's in the middle of the waypoints as so I can back off and cast into the center of them and know I'm pretty darn close to where I want to be.

If you put your Point 1 over your rear transducer, set your console graphs to use that for location and heading and then on your front unit/s use the internal gps for location and point 1 for heading only you could skip a lot of that. No matter which unit you mark from the waypoint will be the most accurate and located where it's supposed to be. The only time that wouldn't be the case is if both units share the same side scan transducer and you're dropping a point off of that.  

[Wayne P.]

3 hours ago, WIGuide said:

If you put your Point 1 over your rear transducer, set your console graphs to use that for location and heading and then on your front unit/s use the internal gps for location and point 1 for heading only you could skip a lot of that. No matter which unit you mark from the waypoint will be the most accurate and located where it's supposed to be. The only time that wouldn't be the case is if both units share the same side scan transducer and you're dropping a point off of that.  

 

 

You are forgetting a little inconvenient detail. To have the same waypoint to sonar return relationship, you have to approach the waypoint from the same direction as when you created it. Otherwise the error will be as much as double when approaching from the opposite direction.

 

The PROPER setup is a transom located external GPS antenna paired with the console unit and use the internal GPS antenna with the bow unit. That way no matter which unit you use to navigate to a waypoint, the GPS-to-sonar return will be the same (antenna and transducer in the same location).

Once created, a waypoint is a location on the planet that can be navigated directly to by anyone with those co-ordinates using any GPS/sonar brand/model.

[WIGuide]

19 hours ago, Wayne P. said:

The PROPER setup is a transom located external GPS antenna paired with the console unit and use the internal GPS antenna with the bow unit. That way no matter which unit you use to navigate to a waypoint, the GPS-to-sonar return will be the same (antenna and transducer in the same location).

Once created, a waypoint is a location on the planet that can be navigated directly to by anyone with those co-ordinates using any GPS/sonar brand/model.

Isn't that what I just said? The only thing I was pulling off the Point 1 in the back was the heading, not the location. Location at the front unit still gets read from the internal gps. The heading just allows the locator to not have to use location history to calculate what direction the boat is facing/moving. Maybe I'm wrong, but the the heading is going to be correct no matter where on the boat the sensor is located, unless the front and rear are no longer facing the same direction and if that's the case, the last issue you'd be concerned about is the accuracy of your waypoints. 

[eddallen]

So I don't Bass fish and I take a slightly different approach. I mark ALL waypoints by placing the cursor directly on what I need to mark. As Wayne P said, after marking the waypoint it is forever a set of coordinates, never to change. It really doesn't matter to me if there is 6 units on the boat, they will all display the same position for any waypoint. You can test this at home simply by placing the cursor over the same waypoint on all units and its LAT/LON will be spot on. Of course, if you want extreme accuracy make sure you are zoomed IN tight. Notice on Wayne P's pic that the EPE (estimated position error) is 19.7 feet. That's almost the length of a Bass boat. I think, from what the OP stated, that he needs to realize the difference between a 2D sonar cone and a DownImaging cone (footprint). Very easy to see and mark something on DownImaging without that item ever getting close to the 2D cone, especially in skinny water.

Really good info in this thread!

[Wayne P.]

I choose equipment with more accurate GPS so I don't have to search the area in the vicinity of a waypoint to find the subject.

Here are some GPS diagnostic screen shots with external GPS antennas that I use:

 

 

 

This is with a Humminbird Helix 12 internal GPS antenna sitting on my desk:

 

 

When I use the H12 on my boat, it is connected to an external GPS antenna with heading sensor for better accuracy.

 

Those with other setups should post their GPS diagnostic results to see what is the current performance. The HDS one I posted was before there was a Point1 GPS antenna.

I had requested those HDS ones as part of a comparison test that I and several others were doing since a lot of units were getting away from external GPS antennas to internal GPS antennas.

 

 

[Wayne P.]

Another example of accurate GPS. This is a brush pile waypoint created a few years before this screen shot with another HB Sonar/GPS unit. In relation to the boat, it is at about 220 degrees. It is displayed on the 360 view at that position and distance. The green ring around the waypoint is a 30 radius and the 360 distance rings are 10'. The position boat icon is oriented with a Heading Sensor.

 

 

 

[gulfcaptain]

I have to say, the way I run mine may not be the best for everyone, but years of using waypoints on a large charterboat hear in S. Cal and having to find the area I'm looking for on the sounder, to me the way I have mine set it's easy for me to transit to whatever waypoint I have and find it quickly on the sounder to which I drop my marker on if it's isolated or a couple to mark an area of interest I want to fish.  Rocky areas in shallow (under 20ft) I use several to mark that area as so I can cast to the area and not run it over and spook whatever fish my be holding there.  Is this best for everyones set up, probably not, buy Wayne is right, a waypoint's data can be used on ANY GPS if you write the numbers down and enter them into another unit.  GPS is WAY easier to use as well as accurate from the old Loran C way of navigating.

[WRB]

GPS way points are accurate, no debate about them. Your boat location is the antenna location, not the transducer location. If your antenna is located near the aft transducer the variance is minimal, if you are using the front trolling motor transducer and the GPS is located at the rear, the variance is the boat length.

Tom

[Wayne P.]

Another reason for the GPS antenna and transducer to be in the same place.

I collect sonar/GPS data to create contour maps and I also do Live contour mapping (Auto Chart Live and Sonar Charts Live).

When my depth readout indicates 10', I want the created contour line to be at 10' with no distance error.

Along with that, I use the depth offset to add the depth my transducer is below the surface so the contour lines are at the actual water depth, not the distance between the transducer and bottom.

Additionally I do not do contour mapping at other than normal water levels unless the level difference can be offset by the depth offset setting.

If I decide to take the time to collect the data, I want it accurate.

 

Those with Lowrance units getting the latest software to have Navionics Sonar Charts Live should consider the addition of an external GPS antenna if they don't already have one placed properly for accuracy.

[eddallen]

17 hours ago, Wayne P. said:

Another reason for the GPS antenna and transducer to be in the same place.

I collect sonar/GPS data to create contour maps and I also do Live contour mapping (Auto Chart Live and Sonar Charts Live).

When my depth readout indicates 10', I want the created contour line to be at 10' with no distance error.

Along with that, I use the depth offset to add the depth my transducer is below the surface so the contour lines are at the actual water depth, not the distance between the transducer and bottom.

Additionally I do not do contour mapping at other than normal water levels unless the level difference can be offset by the depth offset setting.

If I decide to take the time to collect the data, I want it accurate.

 

Those with Lowrance units getting the latest software to have Navionics Sonar Charts Live should consider the addition of an external GPS antenna if they don't already have one placed properly for accuracy.

Great  tips for those starting out and some seasoned vets. You also point out some very real problems for us out west (CA) where our lakes are rarely full or at capacity, and in fact, seem to change elevation on a daily basis. This is why I choose to upload logs to Insight Genesis, where I can create the offset for lake elevation. Currently this is the only drawback to the 'on-the-spot' or 'live' recording programs. Maybe in the future upgrades this will become available.