Flasher Use in Shallow Water

[McGurk]

Here's an odd question: What is the _shallowest_ you have received a good reading using a flasher? I have been asked to do a topography for a few of the ponds in the Bloomington area to get a volumes so we can bid out silt removal. We are going to grid off the sections of the ponds and was hoping to shoot through the ice with the squirtbottle method. I have an LX-3 and will be doing some checking this week as I have never used it shallower than 10 feet. A few other questions...

What is the red band at the top of the flasher at 0-1 feet?

How can you differenciate between weeds and the soft bottom?

Is reading through the ice as accurate as drilling through?

-I really don't want to drill holes when it gets too shallow as bottoming out will dull the blades instantly.

Any thoughts or experience would be appreciated and Thanks in advance. These topo's are on a pretty small scale but still a challenge. Now if I can only get some tip ups out while doing this on the clock...

[Ed Carlson]

It may be more efficient to use combo of a GPS and a flasher.

Set a few known depths on the deepest section of the body of water and then map with the GPS by elevation to the surface of the ice/water. You should get fast and reliable plots and cover a lot of ground quickly. It depends on what mapping data perimeters are most critical for your needs really.

[Ray Esboldt]

If the ice is clear with no air bubbles, you can get an accurate reading shooting through the ice. However, shallow water will give you some problems. The top of the scale clutter will bleed into the actual bottom. If the weeds are not too thick, the LX-3 can be turned way down and will read the bottom with minimal clutter.

I would say you're going to have to combine shooting through the ice, drilling holes, and maybe even using a weight on a marked string to get all the data you need. Ed's right that if you could throw in a handheld GPS, you'll end quite a bit more accurate.

[Walleye Guy]

I would use a hand held GPS and a hand held depth finder like the Marcum LXI. You wont need to drill holes because you can shoot a signal right through the ice.

[McGurk]

Thanks for the replies, guys. I will be using a GPS setup which my work will provide. It is capable of sub-centimeter (yes, centimeter) accuracy when used with a base station. That part I'm not so concerned with.

I agree with using multiple methods to get an accurate read, I was hoping for a little more feedback on the different types of bottoms and weedlines as I haven't been exposed to many different types of lake bottoms. The top red bar at 0-1 feet confuses me too. Like I said, these are smaller ponds that I need to read right up to shore.

[marine_man]

I'd agree with Walleyeguy... find a good handheld depthfinder with a digital readout that you trust (that you have experimented with) and use that.. that way there is no error due user interpretation of where the bottom is, or if that's a weed or the bottom...

marine_man

[mpester]

What brand of GPS receiver do you use? You will need to average your position to receive centimeter accuracy. Way back when I had a job mapping with GPS, our old technology was to setup a base station and average our position for the feature we were mapping. We averaged for 30 seconds to receive 1 meter accuracy. This was when the government still had selective availability running. Data was post processed at the end of the day against the base station data. Better hope the base station works all day. I had a few day where the base station cut out on me and I lost a days work. After a year or two of mapping and post processing data, we got equipment that was real time differentially corrected. That was nice and accurate right in the field. I moved all over the country for five years mapping for E-911, state DOTs and utility companies. I lived in ID, SD, MO, WV, MS, DE and PA. I miss the good hunting and fishing I got to do while the company paid for me to live in these area but I love living here in MN.

[McGurk]

Handheld: Garmin etrex Legend

for work: Leica rover and base station. We aren't able to get a great lock on z; maybe +/-0.07', but the northing and easting are easily accurate to +/-0.02' while using it in real time. The base station and the rover communicate using cell phone modems and we have about a 20 mile range from the basestation while maintaining that accuracy. We have the base station permanently mounted at our office and have spend a lot of time getting that pinned down, so we actually let other Lieca GPS rover users lock onto our base station, too.

[Ray Esboldt]

McGurk,

If you want to try a handheld, you are more than welcome to my Marcum LX-i. However, like I said before, if the ice is cloudy, shooting through the ice is not terribly effective.

Send me an email if you're interested. bornofice @ yahoo dot com.

[McGurk]

Thanks for the offer, I might have to take you up on that. I've got an LX-3 that I'm going to go out tomorrow and test side-by-side with a fiberglass rod with increments and a classic standby; the string and weight with lengths marked w/knots. I'll post a little info after.

Has anyone used a handheld dig. depthfinder next to their flasher and compared them? If the transducers are at the same elevation, will they read the same like I'm sure we all hope?