handheld depth sounder

[johnnyq]

Originally Posted by Beppe123

Has anyone experience with a reliable handheld depth sounder ? I am looking for a new slip in the Annapolis area and measuring depth with a metal tape does not seem too reliable due to the soft mud bottom. Thanks.

I’ve used the Hawkeye as well. Worked like a charm in the Caribbean. Gives you water temp and depth in either meters or feet.

[Laxlife]

I have used the Hawkeye DepthTrax flashlight sized handheld depth sounder for several seasons. It is accurate and easy to use. Depth only, it is not a fish finder. I can probe shoals and small channels from my dingy which has come in handy. I have tested its accuracy at my slip and my installed depth sounder and my lead line verify the accuracy of this little handheld.

[cdcorl]

We keep a lead line on the boat as a backup. The old methods still work! Nothing more than a 50’ line with a lead at one end to bring it down. You could use one of these and keep it in the anchor locker in. Are you ever need a spare.

[gs41escapade]

Originally Posted by Beppe123

Has anyone experience with a reliable handheld depth sounder ? I am looking for a new slip in the Annapolis area and measuring depth with a metal tape does not seem too reliable due to the soft mud bottom. Thanks.

I use just a PVC pipe (up to 10' X 1") that I marked off in 1' intervals with a sharpie. You can feel where the mud starts as you put it down. I guess for more accuracy, you could put an end-cap or even a square of plywood on the end for a broader surface.

[Mjames]

I bought this one and have been extremely pleased with it. VEXILAR INC. Vexilar LPS-1 Handheld Sonar Depthfinder 24Deg 2-200'

[rupertfb]

The word 'accurate' is seen here quite a lot. A depth sounder is subject to many errors, some of which you can reduce, some you can't. Here's some of the major ones to consider!:

1. Vertical positoning: A depth sounder should be calibrated such that the depth reads from the surface, so that 'depths' may be compared against the chart. Most people don't do this, preferring to know how much water is beneath the keel. However, the DS is rarely mounted at the deepest part of the keel (it'll get knocked off) , so this incorporates error too, and when used in this style, you also lose that 'comparison against the chart' bonus.
2. Different frequencies penetrate mud/silt to different depths. Higher frequencies reflect off the soft stuff, lower freq' penetrate deeper....sometimes much deeper in areas of deep soft mud. 100KHz and 200KHz are common, but 400 and even 1,000KHz are available.
3. Speed of sound in water changes with temperature and salinity. faster in salt water than fresh. Recreational DSs rarely allow you to measure or change the SoS in water
4. Location of transducer horizontally; Although not an error as such, it's clear that the further forward you place the transducer, the more use it is to you (not much use if its mounted aft and tells you that you just went aground). However, too far forward and it may be subjected to air bubbles from pounding. Air bubbles absorb all the energy of a 'ping'. Classically, people mount the DS 1/3rd of the sub waterline hull length aft, in compromise between these two considerations.
5. A lower frequency transducer pings in a cone extending about 30 degrees away from the vertical. Thus a shallow rock to the side of your path may give you a 'false' depth that you would otherwise assume is under you
6. Multipath: A ascending ping can reflect off the hull back to the seabed and back to the hull, giving you a reading of about double the real depth. Although rare now (with better filtering software), they are more common in shallow water.

In conclusion: A Depth Sounder, just like your chart, or navigation system, or AIS, or RADAR is just another tool in the bag.....its a great tool.....but ultimately all of these tools are subject to errors or ommisions, and data from them should be regarded as (extremely) helpful, but not absolute.

Rupert Forester-Bennett
IHO Cat A Charge/Command Hydrographic Surveyor

[sailingharry]

Originally Posted by rupertfb

The word 'accurate' is seen here quite a lot. A depth sounder is subject to many errors, some of which you can reduce, some you can't. Here's some of the major ones to consider!.

Rupert Forester-Bennett
IHO Cat A Charge/Command Hydrographic Surveyor

You sound like you have quite a bit of knowledge in the area.

Discounting your number one, which is a user error and not a system error, can you put a measure of the error on modern recreational depth sounders? I'm sure that at some level the error is a function of depth, although at depths over 15 ft most of us don't care much at all (a 5-ft error in 50 ft deep water is rather inconsequential). In the three to eight foot range where we care a lot, what sort of errors are we likely to see?

[sailingharry]

Originally Posted by Beppe123

Has anyone experience with a reliable handheld depth sounder ? I am looking for a new slip in the Annapolis area and measuring depth with a metal tape does not seem too reliable due to the soft mud bottom. Thanks.

We went through this over the last several years as we searched for our retirement waterfront home. Real estate agents are notoriously optimistic about water depths, much of it due to complete ignorance in the subject.

I took a ball of braided fishing line (bait casting line?). Our boat draws 7'. On one end tied a large nut, but most any weight would do. I then tied on the string at 5, 6, 7, and 8 ft marks a 2 inch long piece of quarter inch dowel. I could easily toss this out in the middle of a slip and in the approach to the slip. Count the pieces of dowel that are pulled under water, and you know the depth. If the 8-ft nark is underwater, I started to lose interest, although I could estimate up to about 9 ft.

This link will give you real time actual tide in annapolis. Not predictions, actual measurements. Very helpful when assessing a potential slip.
https://tidesandcurrents.noaa.gov/wa...tml?id=8575512

[rupertfb]

Excellent question 'SailingHarry'!

I'd suggest the biggest error is the calibration: In a 45' sailboat (for instance), most folks will position the DS on the hull around 3' deep and not calibrate the error out. This gives a fixed error of significant magnitude whilst at the same time reading neither a) depth under the keel, nor b) waterline depth

The next largest error (in response to the author's original question) is another fixed error: the author was interested in readings in soft mud. My text explains where this error originates.

The first variable error of note would be the SoS in water error which, as you correctly point out, is variable and actually of little importance in shallow water. However, I use contours at deeper depth as a 'line of position' to increase positional confidence and, at depth, the SoS errors multiply to proportionately greater numbers.
In saltwater, sound travels at about 1500 m/s and in freshwater 1435 m/s. Most recreational DSs use a fixed figure of 1500m/s. If you were to be in 10m of water, the difference (as you enter fresh water) would be 0.45m (1.5')

R

[JBsurfin]

Originally Posted by Beppe123

Has anyone experience with a reliable handheld depth sounder ? I am looking for a new slip in the Annapolis area and measuring depth with a metal tape does not seem too reliable due to the soft mud bottom. Thanks.

I have one of these and found it to be pretty accurate, I only use it in the dingy investigating new anchorages. So anything under 15' has been pretty spot on.

Hawkeye DT1H Handheld Depth Finder with Temperature, 300 Feet

[Mike Vogdes]

I use handheld depth finder by Speedtech Instruments, 10413 Deerfoot Dr, great Falls VA 22066, 703-759-0511. This thing is great, well built and very accurate.

[parkstone bay]

The OP wants this for a specific one-time purpose, so there's no point in spending any huge amount of money. A large shackle on an appropriate size line will do the trick.

[Nepidae]

Partly, it depends on future use.

I got one, similar to this (https://hawkeyeelectronics.com/produ...d-depth-finder) that I use on the dinghy. I find it accurate, to the extent I can without hand measuring to check it.

[hjohnson]

We keep a traditional marine Lead Line on our boat for this purpose. It’s a heavy weight tied onto about 30’ of marked thin line. Lower the weight over the side until you feel it touch bottom.

Very useful when anchoring in the fjords of the Salish Sea, as our depth sounder is forward of the keel, which means that when stern tying, the depth can be significantly different at the aft end of things.

Also, the weight has a cupped bottom, which we can fill with sticky peanut butter or similar, and hopefully get a sample of what’s on the bottom. (Sand vs mud vs stone).

Got it for free from a junk bin at the boat show.

[NYSail]

I bought one called HawkEye Depthtrax 1H. Gives depth and temp. Works great. Nice to have when checking out new anchorages