Often when I record sonar logs on my HDS I get lots of inexact depth readings. They can be out by up to 2 metres or more. They show up OK in RM in the viewer and I can correct them but it can be cumbersome.

Now I realise there are a lot of external variables that can affect the sonar log recording. I'm wondering if there are any internal settings in the HDS that I could change to improve my recordings.

I don't have the luxury of a nice calm lake to record on so I often have 1 metre plus waves to contend with. Maximum depth is around 50 metres. I'm looking for any feedback that would help.

Meggs

Making sure transducer is fitted perfectly is one major parameter in having "good" logs, as well as not going too quickly. 2m difference if going slow is a big error.

Don't really know any settings in the HDS affecting this, transducer angle is probably most important.

If you have an old standard 200/83 Lowrance transducer it might be a good idea to try another transducer if possible. I have found they wear out after a few years. Airmar-transducers seems to hold up better.

What ping-rate are you using? Crank it up to 12-16+ if it's low.

As Martin said, this sounds like an issue of bad ducer placing, or at least bad ducer adjustment. Do you have a photo or ten of your current setup? What ducer are you using? Do you have LSS, and if you do, does it show the same bad readings?

Thanks for the input. I've been considering relocating the transducers and have just ordered a new 200/83 KHz transducer. Good idea Martin - I remember replacing a transducer on a previous boat and getting improved performance.

As you can see from the picture the transducers are currently on the "wrong" side (port) so are more likely to be affected by the propellor wash.





Boat is a 5.2 metre Runabout (Australian - Webster) which is an aluminium, twin hull, single outboard configuration. I plan on relocating the transducers to the starboard side and mounting them closer together. This will mean getting a custom sliding bracket made to accomodate them. The sliding bracket is necessary for beach launching in shallow water.

@Team Colibri - ping rate is set at 15. Downscan and StructureScan (LSS-2) also shows errors but not as pronounced.

That happend time to time because on great wreck botton go from 80m to 60m as a wall so need to correct! that the plus of RM from other soft to the possibility to correct!I do most map from Wreck and get great diffrernce with correction or not (I uise an AIRMAR TM258 1 KW cone angle at 5°) Divers reconize map and can tell which wrech it is!
Little question can I get where I can get rail support of transducer on picture here in France not good produce sell!! TAHNKS!

@nitro78

Here are some links to 3 different types of adjustable brackets from a major Australian supplier. I believe all of these are made in Australia.

www.whitworths.com.au/main_itemdetail.as...r+&intAbsolutePage=1

www.whitworths.com.au/main_itemdetail.as...r+&intAbsolutePage=1


www.whitworths.com.au/main_itemdetail.as...r+&intAbsolutePage=1

The stainless steel version is more suitable for larger transducers. Maybe a French retailer could source something for you.

Meggs

Here is a swedish one. Quite expensive but good (use it myself):

www.linder.se/index.cfm?x=product&pg=7&pr=24

Language can be changed on that website BTW :)

Fits a LSS-transducer and Airmar P66 side by side

nitro78 wrote:




Crappy photo, but it shows my ducer-rail, and the new one that I just got. Will be using one on each side of the outboard. Mine are from a Finish boatmaker: www.silverboats.fi Your TM258 is a bulky piece of kit, so make sure the rail and mounting-plate can handle the weight. Most rails like these are made to hold the small OEM ducers, not aftermarket 1KW ducers with 5 times the weight.

@Meggs1:
What worries me is that you have the same problem with both ducers, this might be a problem with your HDS-unit. I'm guessing you have this problem even when the bottom is flat as your livingroom floor? You have the latest SW on your HDS? You have tried a soft reset? (Save your settings and waypoints to a memorycard first.) What sort of speeds when the problem occures? Does it happen when you drift or when reversing as well?

You might be right with propellerwash, but I'm not sure. If it's the propellerwash, you should have no issues when drifting.

Both of your ducers have wide coneangles. This is great for finding fish, but gives less accuracy for depthreadings. This is the reason for me asking if the problem occures on flat bottom as well. In steep terrain your ducers will "jump" from one depth to the next, but the LSS-2 will do less of it since it's cone is narrow in the direction of your boat and only wide across the direction of your boat. (The 83/200 has a more rounded cone, the LSS-2 is VERY oval.)

I missed the part of your boat beeing a catamaran...

I might be fooled by cameraangle, but your ducers are really close to the edge of your hull, ie in disturbed water. Transom mount ducers on cats are always a bit risky, not much clean (buble free) water behind them. I would move them closer together, to the center. It also looks like there is a small step just to the side of the LSS-2, this would defenitely cause disturbed water. But I have no personal experience with cats, sorry.

Thanks Team Colibri - I agree the twin hulls do cause a lot of turbulent water. As for the HDS itself, I haven't tried a soft reset. It does have the latest update. I am also going to try a different setting under "Fishing Mode" for the sonar. I have been using the default (General Use) but will try the Shallow Water option. Not sure what the differences are between these settings but it won't hurt to try them.

Plans for the near future are to use a larger slide rail (to accomodate both transducers) and mount it on the starboard side nearer to the centre line of the boat.