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Yes sir, mine is a Seahawk.
I target trophy Blue Catfish on the Missouri and Mississippi River systems.
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Yes sir, mine is a Seahawk.
I target trophy Blue Catfish on the Missouri and Mississippi River systems.
Nice looking rig.
If I ever decided to stop bass fishing and moved to salmon North River would be the way to go, of course they are in my back yard so to speak.
Awesome boat. Wouldn't change a thing about it
cgesling, without asking too much, do you use your setup to target the fish or structure?
Not sure if this is hijacking or not, because I admit to not reading or even understanding every point in the thread.
My Point 1 is a about 1-ft from my rear transducers and have two 9's at the console. When setting waypoints using downscan or 2-d, I move the cursor to the center bottom of the stump or other object and usually am very close if not dead on. I don't have a technical argument to support doing it this way, but it seems to work well.
It just occurred to me that I might be better off marking an object that I have passed directly over with the downscan screen rather than the 2-D screen because of its narrower cone angle.
Schins-
The answer is yes. I use it to Target both. Just depends on the time of year. Most fish I catch I'm seeing before I catch them. Especially, bluecats 35# on up, they have a very discernable shape. 70-80# fish stick out like a sore thumb when they are active in 4-5+ mph current.rps20170723_071644_338.jpg
Sometimes, if you can discern it's a probable catfish, just measure them so you know if it's worth your time, this picture should be close to a 40# fish... Ended up weighing low 30s I believe... But even still it helps to not be complacent and settle for fish that aren't worth your time- especially in a tourney.rps20170723_073019_410.jpg
I think that's why the relativity of this conversation sparked my interest. I think on slow days the fish may move 3 or 4 feet to eat, but not 25-30ft. And of course on the good days, when they are extremely active if you can just get in-line upriver from them it seems like they'll move 50+ yards out of structure to come eat.
The structure I focus on is primarily brush or laydowns- but I don't spend much time fishing around brush where there wood is only as wide as your arm- even if there's a lot of it- they seem to be more at home in trees you can't reach around and that don't vibrate in the current. rps20170723_071856_438.jpg
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Big slab rock reventment is another- similiar to what you find on the lower Mississippi when it's 100 ft from the bank in 40+ ft of water. On the Missouri River, Big rock on the channel line holding brush really interests merps20170723_072538_492.jpg
Don't want to sound uncomplimentary- but I really wish lowrance would improve their horizontal resolution such as they had with the LSS-1 for downscan- or have a user defined scroll speed for Structure Scan images... Similar to water depth have it automatically adjust for speed, but have an A+1, A+2, etc to give better horizontal definition of your target. The lss2 was compressed down 40%, I'd venture to say that the 3D is slightly more. Scanning on structurescan, I've had to slow down to 2.5-3 mph to get distinguishable images. But, I'm still catching fish I'd never have caught without a graph.
Csurp-
Really depends on the depth of water and the cone angle your using on 2D. But, by practice, marking on downscan is an absolutely great way to mark more precisely- everything else being irrelevant.
By using a Point 1 you have greatly enhanced your accuracy- by using it at the transducer you have improved your marking accuracy as much as you possibly can with current technology (although, I've no experience with the precision-9 compass and have yearned to be able to test it). http://www.simrad-yachting.com/en-US...ass-en-us.aspx
It may not improve accuracy as much as picture quality on mosaics due to Course Over Ground filtering and correct heading info. Humminbird struggles with mosaic heading as well and this is a NMEA2000 compliant device so it should work on either in my novice understanding.
Not pointing any fingers or wishing to start an argument but this may be a good thread to point out the difference between "precision" and "accuracy".
"Accuracy and Precision:
Accuracy refers to the closeness of a measured value to a standard or known value. For example, if in lab you obtain a weight measurement of 3.2 kg for a given substance, but the actual or known weight is 10 kg, then your measurement is not accurate. In this case, your measurement is not close to the known value.
Precision refers to the closeness of two or more measurements to each other. Using the example above, if you weigh a given substance five times, and get 3.2 kg each time, then your measurement is very precise. Precision is independent of accuracy. You can be very precise but inaccurate, as described above. You can also be accurate but imprecise.
For example, if on average, your measurements for a given substance are close to the known value, but the measurements are far from each other, then you have accuracy without precision."
see: https://sites.google.com/a/apaches.k...y-vs-precision for another explantion and some graphics.
Csurp-
I thought you'd find this video interesting. This was done by John Easton (Fishton) with Fishtec. He's got an incredible mind for sonar. When you watch the video- really digest what he explains about the "fish you can't see on your sonar" and reference drop-shotting and ledge fishing/graphing.
A great example of why you try to use all the data your getting to make the best decision, and know the capability of that data.
Thanks!Originally Posted by cgesling
Don't thank me. Thank Fishton. I'm learning all the time... Or try to.
Knowing from the outset that this entire discussion is based on a false assumption, I have tried to back out and just say "whatever". But the extreme complications here are giving a false premise.
However. that said, everything downstream (pardon the pun) from the placement and look angle of the transducer is riddled with variables that render the "assumptions" totally wrong and demonstrably inaccurate.
In my classes I teach this using a whiteboard. But let me illustrate.
Stand on a ladder and shine a flashlight from 8 feet on the floor...Draw a circle around the "cone" and place a tape mark dead center...that is your "stump target" ASSUMING the light (transducer) is looking perfectly vertical, straight down...which it is NOT on your boat. ERROR to start with.
Now tilt the flashlight 15 degrees or so and mark a new circle and tape spot. This is to illustrate where your transducer is really looking and what you are seeing (marking) on the screen is NOT where you think it is. The "cone" is not distorted, elongated and the "stump" target you are marking (actually at the ladder/light, is actually 20 or so depending on water depth from what you assume is straight down...when it is not. This destroys all of the discussion on what is accurate from the false beginning assumption.
I use a Suunto optical inclinometer on my setups to measure approximate bowrise THEN adjust the transducer look angle to simulate idle compensation. ALL approximate of course. This is ALL inaccurate to some degree and based on assumptions, but the gross assumptions and (I agree with Edd) ludicrous gymnastic calculation process... should be eliminated to get it at least "closer" to what you see is marked reasonably close.
The assumption (incorrect) is that the transducer face is looking straight down, illustrated in Fishtons picture...BUT in ALL cases when the boat, even stationary, unless compensated, will NOT be looking straight down. Transom down, bow up...angle significantly changed and cone moved forward based on the new and variable angle due to boat orientation.
Now add in the increase in bowrise under idle (typically searching and marking) and the bowrise significantly increases...so much that what you THINK on screen is directly under the transducer is actually, possibly 20 feet in FRONT of what you think is under the boat. (refer to the tilted flashlight simulation).
This is exactly why when you see a "stump" on the screen at idle and throw a marked buoy over your head behind (where you think you are seeing) that you have difficulty and the marker is NOT over the stump since the stump seen on screen was actually 20 feet more or less in front of the marker...depending on the assumed straight down view (what you think) and where the transducer is actually seeing and showing the target.
SO, virtually ALL of the statements and assumptions on all of this LAT/LON marking vs screen vs head unit vs antenna over transducer is all 100% inaccurate...from the beginning.. because the unknown look angle/mounting of the transducer varies per installation and proper adjustment. EVEN WORSE...is that in a bilge mount (on a flat bilge surface) that (interior mount plate) is typically "flat" based on boat construction with no compensation for anything. So the transducer is automatically tilted forward when in the water, when stationary from the beginning and much worse underway AND that CANNOT be adjusted since it is epoxied so any claim of accuracy is bogus at best.
I teach and illustrate this in my seminars and even carry whiteboards to do so. In a high school bass club seminar I illustrated this and they all were amazed at the inaccuracy and false impressions they have been depending on...This is NOT complicated at all...common sense and simple high school first year geometry.
If anyone doubts this illustration, grab a flashlight to illustrate and then calculate your boats bow rise stationary and at medium idle. This is very simple.
Tommy
Prostaff Lowrance/Navico
Prostaff Marine Specialist/Navionics
Last edited by prostaff1; 07-23-2017 at 09:10 AM.
I've always pondered that. I try to keep as consistent as possible while graphing as far as speed is concerned.
What do you teach for transducer mounting and leveling do you level your transducer at idle/ graphing speed?
On your transom mounted 2D ducers I like to carry mine a little higher than the bottom of the boat so I can read on plane- or up to 50 mph anyway. Which I don't think would affect a 20degree 200 mhz cone, but if placed more than an inch or so above I may start interrupting my 83 mhz cone at 60 degrees. What is your preference?
I always thought manufacturers recommended a slightly forward looking installment?
You would think they would set the unit up from the factory to include this when marking.
cgesling, thanks for answer on your targeting. Here on the Allegheny around Pgh our catfish top out at about 40lbs and we have precious little structure and depth.
The video by fishton is from his books where he explains the issues in this thread and talks about correct transducer installation.
i think the manufacturers need to have a more detailed installation process in their manuals about correct levelling of the transducer relative your use case. For example I set my transducer angle for 4 degree bow rise which is for mapping and fishing and run a point 1 straight above my transducers
Wow, now that was both entertaining and educational with a lot of effort put in by both primary parties.
The Objective: -
At the end of the day, we want to return to that 'special spot' we found a minute, an hour, week, month or year ago and fish it accurately as we would pitch to visible cover along the shoreline.
The Tools: -
Between GPS, 2D sonar, DownScan and SideScan technology, it is actually a lot harder to create a 'timeless' accurate waypoint than one would think.
The 'Hurdles': -
GPS
a. GPS is not all that accurate and can fluctuate dramatically in a very short time without noticing unless you had an alarm on you EPE value.
b. GPS receiver location to the transducer from where the waypoint was created plays a very big part.
Sonar
a. Cones and beams are not 'laser pinpoint' measurement devices due to the cone size of 2D and beam width and heading of DownScan and especially SideScan.
Preventive Measures: -
a. Mount Point-1 puck as close to transom/in-hull transducers as possible.
b. Under network, data source, GPS - change Scope from default Global to Local.
c. Still under network, select Point-1 for console unit, and This Device for bow unit. (critical to do steb b before doing this)
The only thing you could do to improve this further is to add a radar type sonar such as the 360 to run along side your Lowrance bow unit to give you a 'Live View' of the proximity and heading of your target as you approach it.
Last edited by Fishton; 07-26-2017 at 12:59 AM.
Fishton,
Being from South Africa, the GPS you use would be autonomous correct?
The geostationary satellites that have the WAAS almanacs would be so far to the north west of you that you may not be able to talk to them.
So, to that affect, you could use GLONASS, it'd have to be filtered I'm sure. Last understanding I had on GLONASS was we could receive GLONASS with autonomous GPS- but we can't utilize GLONASS with WAAS differential correction. Because you can turn both of them "ON" within the Lowrance, I'm not exactly sure which one is given priority.
Do you have access to Galileo? It is equivalent to our WAAS- possibly slightly better. Usually the HDOP would improve slightly at the higher latitudes simply due to geometry and the satellite mask that's user defined. Due to your location in the southern hemisphere it may cause more inaccuracies than it helps. Your AOD would be interesting.
All in all, it doesn't matter- everything you said was correct- this is purely curiosity- could you screen shot your GPS diagnostics sometime. I've not traveled to Europe or South Africa in near a decade. With the improvement and reliability in Algorithms such as GL1DE- maybe WAAS or Galileo or BeiDou are futile for future needs. GL1DE should work with small smart antennas, any L1 band, and improve accuracy dynamically as well as stationary- and for a fishermen it could help limit multipath errors due to bluffs/mountains/buildings- very seldom do great fishing spots have great access to the entire sky.
That's for the input John.
cqesling, thanks for the data, I was curious about this my self and found the thread in a search. I agree that when using the hds unit as the antenna, there will most definitely be an offset between the image on screen and the actual location of the structure, if the transducer is say 5 or 10 ft from the antenna. Even when tracking back and using the cursor, the gps location associated with the image would still have the offset between the transducer and the image (based on horizontal plane). If this were not the case the why would anyone need to install the puck closer to the transducer for accuracy. Great data, and I gather from reading this thread, there is no way to program an offset into a unit? Maybe I missed that part. Thanks!
Wow. Revival of a two year old thread... But the information is just as prevalent now as it was then.
Still to this day, there is no way to put in a fore/aft offset ( from GPS receiver to transducer location).
Still to this day, there is no water level offset either (kinda fustrating)... But you can manipulate the sonar installation to account- but it's a backdoor way of doing it.
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