Be careful with Quickdraw

[Larry3215]

Someone posted a question about Quickdraw and that reminded me, so I checked to see if anyone had posted any new recordings of lakes or marine areas I fish. Turns out there was some new stuff, so I downloaded it and took a look at it after up-loading it to my 7610.

Potholes Res. is a lake I have fished a number of times and some of the areas that were recorded I happen to know pretty well. This is not an HD or max def lake that Garmin has surveyed, but the Garmin chart is still pretty accurate over all. This happens to be a lake that can change water level pretty dramatically, but it looks like these recording were done at full pool or close to it.

However - there are some glaring errors and inaccuracies that could be dangerous if someone downloaded this QD map and relied on it to stay out of trouble. It shows water 30+ ft deep in places that are well up on dry land and deep water where is it 1 or 2 ft deep at most at full pool.

I dont know if the person recording this file had the offsets wrong or maybe their GPS was off or what. I wont go over these in detail. You can easily see the differences between the Lakevu chart vrs the QuickDraw charting and how the shore line gets over drawn and impossible depths are shown near and even on shore.

The point is - never trust QuickDraw for navigation or safety when boating!!

For one thing, you have no idea if the person recording it knew what they were doing, and QuickDraw has several quirks that make it impossible to trust near shore. All of that gets even worse if water levels are changing.











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[Larry3215]

A couple more.

In this one the water depth is 6 ft or less.








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[Riccochet]

I've found the stock shoreline only maps to be highly inaccurate. Which is probably the case here. I've been on a few local lakes in 10+ feet of water, that is always water, and the map showed me on dry land.

[Larry3215]

No, the shoreline shown on the chart for this lake is pretty accurate - when the lake is at full pool.

Garmin QuickDraw takes the depth it calculates under the boat. and draws that depth as a constant, wide contour line all the way to, and beyond, the shoreline, if you are close enough to shore. This over writes the shore line on the map so you cant see it. It will also over write - and hide - shoals, rocks, islands, nav aides, and other hazards that are near, but not directly under the boat.

Any shoreline drawn by QuickDraw will always be wrong - always.

In this particular case, it is showing depths that are 30-40 ft deeper than they can possibly be, very near and even ON the shore.

[msn26753]

Agreed 110%... QuickDraw should only be used for fishing reference only, not running or sooner or later you will be sorry.. When Im Running the River, I always turn off Quickdraw overlays... Its way too Dangerous.. Theres a Rock Jetty that Quickdraw doesnt show and its about 10 Foot Wide and Miles long, But since you fish both Sides, Quick Draw does not pick it up and connects the dots to where its not even their.. So If I was running river and looking at quickdraw, I would be lucky if all I lost was a motor...

[puhlw]

Quickdraw reminds me of SI, kind of misleading from the manufacturers. Looks great on the commercial but in practical use not as great.

With that said I haven't tried it with my PS30 yet so hoping that changes my opinion.

[LWINCHESTER2]

...........I haven't tried it with my PS30 yet so hoping that changes my opinion.

It will.

[Larry3215]

I would love to see a side by side comparison of some scans near shore, or near a rock shoal, jetty, or some other obstacle or hazard with the PS30 and any other transducer.

I would hope it would draw the actual contours based on the 3D capability of the PS30 and do an accurate fill in out to the sides.

Have you tried this Leonard?

[LWINCHESTER2]

I have not done a fair comparison. I have used both the GT50 and GT51 with Quickdraw on areas that I already knew quite well. It took repeated passes with some overlap to get a good accurate map. What I see with the PS30 is wider coverage. I still overlapped some but with the wider coverage there was a clear gain in how quickly an area could be mapped. Also I could significantly increase boat speed without degradation. Overall I would say that I could map an area with the PS30 in a third of the time to map it with the GT50 or 51.

Sorry, I don't have any of these files anymore. I deleted them when I got the 2017 map. Garmin has mapped my lake with 1' contours and after studying it extensively it is very accurate. When they mapped Fontana we were not quite at full pool so the full pool shallow areas were missed and our lake levels change to drastically over the year that it is critical to enter the offsets based on the current level. Not very difficult. I just check the sonar depth and then adjust the map offset to match it. It's a daily thing though as we will be dropping from 6" to 1' daily until Dec 1.

When I was using the GT50 or 51 I would see occasional areas that dropped a foot or two or rose a foot or two making a hump or depression that was not there. The problem is that I had to already know that to know it was an error and then know I needed to make another pass for it to be corrected. To me this means that all of the area to be mapped has to have repeated passes; not just a pass to tie into existing coverage, but an actual repeat pass. One pass cannot be relied upon. I did not see these errors on the PS30, i.e. showing things in the center of the coverage area that I knew were not there. I would be comfortable mapping an area with the PS30 using single passes with 1/3 tie overlap from the previous pass. I wouldn't bet the farm on it, but I made it a point to map some areas with unusual features and it looked really good. If I was using the GT50/51 I would do at least two passes and still do the 1/3 overlap tie. It's like using a fast internet connection. Once you have one, you can't take going back to a slow one.

[Pokerbill]

I have noticed when moving along a sharp drop off like a river channel ( say 15 to 45 ft deep) recording with Quickdraw that when I come back later to fish the area that some of the deapths are wrong by quite a bit. Is part of the near shore issue or is there something else I am missing?

[Larry3215]

I have noticed when moving along a sharp drop off like a river channel ( say 15 to 45 ft deep) recording with Quickdraw that when I come back later to fish the area that some of the deapths are wrong by quite a bit. Is part of the near shore issue or is there something else I am missing?

I suspect that where there are slopes and rapid changes in depth. that even small changes in your path will make large differences in the "depth" that gets recorded. The problem is that, with regular transducers, the "cone" can cover a pretty wide area. In your case with 45 ft deep, the cone might cover an area anywhere from 10 ft circle to a 50 ft circle depending on the specs and frequency and settings. Garmin doesnt tell us how the MFD decides what to call the official "depth" when there is a slope, so I have no idea how they decide that. I know its not the shallowest point in the circle and its not the deepest point in the circle, so Im guessing its some sort of average, but thats just a guess.

If the depth varies from 15 ft to 45 ft within that circle and Garmin decides the official "depth" is 20 ft, then there are always going to be errors. It could also be that moving a few feet one way or the other changes the average a bunch ans then you will still have errors.

I am starting to think that Quickdraw isnt all that usfull unless you have a PS30 or th bottom is fairly flat with slooow depth changes.

[Pokerbill]

Hum.. Base map in MFD of the water I fish is in meteres, not feet, and not likly to get fixed soon. That was managable until I started to chart a lot of the lake with Quickdraw in feet. Really getting to a point where I am not sure we which contours are in feet and which are in meters Talk about dangerous. ( I know there is a disclaimer. ) Now I fine the readings from Quickdraw might be way off. I guess if I want a contour map of my home lake I might have to take a different path. Seems silly isn't Garmin a mapping company? Hello.

[msn26753]

When you set up unit it should have asked meters or feet.. I think you can change it in settings... I know I seen it in there..

[Pokerbill]

Not the problem. When Garmin programed the chip they used data from a USGS map which was created in meters. I have the USGS map. Garmin programers made an error and showed those contours orginally created in meters as feet on the Garmin Chip The "numbers"on those contours cannot be changed. If those are the only "units" you are working with can devide by 3 to get feet

I could change the depth reading on the MDF to read in meters. Cannot change the map depths. Not sure how useful that would be, no math I guess. Most of my fishing is in 25feet of water which means my units would be 1meter though 5 meters. If I am in less than 1 meter of water I sooner the unit be reading in feet.

Cannot change Quickdraw. Programed only to record in feet. So half my contour lines are in feet. Half the contour lines are in meters on the same map. I can live with it, just frustrated. These units cost a lot of money.

[Larry3215]

You should notify the cartography department about that error. Maybe they will eventually fix it.

As far as the limitations with Quickdraw and depth errors - ALL user operated sonar based mapping has exactly the same issues.

Quickdraw has one huge - potential - advantage over all the others in that you can use a PS30 to map with. If I am understanding Garmn correctly, and if they are telling the truth, the depth contours should be accurate for the full width of the PS30 beam on each pass. That should eliminate most of the problems with accurate contours - even up close to shore.

However, Garmin has been far less than truthful on other things, so I want to see this in action before I say its true and start depending on it.

[Pokerbill]

Thanks Larry, Have notify Garmin Cartography about the issue several months ago. It is 20 miles of water and part of an HDMap so I felt I should bring it to thier attention. Even was assigned a case number and followed up with emails but tunes but never received a reply. "Expecting" Garmin will make adjustments next year with the new updated maps, at least I am hoping. I was thinking given enough time I could map all the areas of interest with Quickdraw until I realized that might not be possible.

[Todd Driscoll]

Thanks Larry, Have notify Garmin Cartography about the issue several months ago. It is 20 miles of water and part of an HDMap so I felt I should bring it to thier attention. Even was assigned a case number and followed up with emails but tunes but never received a reply. "Expecting" Garmin will make adjustments next year with the new updated maps, at least I am hoping. I was thinking given enough time I could map all the areas of interest with Quickdraw until I realized that might not be possible.

No doubt, if you are serious about making QuickDraw maps most efficiently, the PS30 is the way to go. 12X more efficient that with a single beam transducer.

[Larry3215]

No doubt, if you are serious about making QuickDraw maps most efficiently, the PS30 is the way to go. 12X more efficient that with a single beam transducer.

Ive seen a few reports supporting the increased efficiency using a PS30 including Leonards. Efficiency isnt necessarily the same as accuracy.

My questions is - are the recorded depth contours accurate - for the full width of the beam - on a single pass - including on steep slopes and against the shore?

In other words - does the PS30 really eliminate all the problems Ive outlined above?

[Todd Driscoll]

Ive seen a few reports supporting the increased efficiency using a PS30 including Leonards. Efficiency isnt necessarily the same as accuracy.

My questions is - are the recorded depth contours accurate - for the full width of the beam - on a single pass - including on steep slopes and against the shore?

In other words - does the PS30 really eliminate all the problems Ive outlined above?

No question, the PS30 is very accurate with just single passes. The only exceptions would potentially be the shoreline or creek channels that have a high amount of turns, S-bends, etc. (multiple passes can tighten these up). However, I would suggest that these exceptions also apply to even the highest-end multi-beam technologies.

[Pokerbill]

No doubt, if you are serious about making QuickDraw maps most efficiently, the PS30 is the way to go. 12X more efficient that with a single beam transducer.

Expected a few thousand dollars of recently updated electonics would meet my expectations . Guess not, another $1500 might get me there? Or maybe not? I still remember how excited I was when I purchased my first Hummingbird Flasher nearly 50 years ago. Electronics, can't always justify buying them, can seldom justify fishing without them.