looking for structure with waypoints

[blanked]

i have some waypoints that have marked some structure in appox 10 to 12 feet of water.  typically when i reach my waypoint destination i spend considerable time trying to locate the structure with my depthfinder.   these waypoints were from someone else and for the most part eventually i find it.  what i want to know is first does all the commotion of running a trolling motor on low speed and the sonar spook the fish in 10 feet of water when i am going round and round looking for the structure?  second would it be better to just work the area thouroughly with lures instead of first trying to locate a specific brushpile or whatever on the depthmeter?  any inputs?

[Nick B]

Do you keep your TM on a constant low speed or do you turn it on and off. I know turning it off and on can spook fish.  Personally I would find the structure with my outboard running and then mark it and sneak in with the TM.

As for sonar Im not sure at what depth fish get spooked

[RoLo]

By all means, pinpoint your structure first, otherwise you'll never be able to assess its worth.

Anchor down if necessary, but do so upwind of the structure.

If you think that your commotion has disturbed the site, kill a little time with your logbook,

enter the waypoint description, weather conditions and maybe enjoy half a sandwich.

Then begin working the structure that you now have under wraps.

Good question by the way.

Roger

[Garnet]

Even with entered way pts you should get reel close are you stepping your zoom in each time you get close.

Garnet

[RoLo]

IMO, a worthy structure is its own zoom-in (coming up or going down).

I personally would lose interest in any structure in 8-10' of water that required a Zoom-in.

Maybe I'm all wet, but I avoid zoom-in and zoom-out when pinpointing structures,

because I believe that forced familiarity with 1X gives me the truest perspective of bottom contour.

Higher magnifications exaggerate reality, where you may begin to see structure that really isn't there.

Roger

[Garnet]

I'm zooming my GPS to get very close to a location.

Garnet

[Guest ouachitabassangler]

If I don't drop right on target nailing a waypoint I use the outboard navigating grids to pinpoint a waypointed object. Hand-me-down waypoints are only as good as the care taken in making them. One GPS position fix with boat moving won't be very accurate. I let a waypoint collect at least 10 pings, the unit averaging positions. Bass are used to hearing motors pass overhead, usually not associating that noise with angler threat. Once I think I have the spot I'll zoom down at least to better spot any fish around the structure. The idea of zooming is to eliminate upper water column portions not holding bass. I was on a deep hump last week with post spawn in full swing, the top of it 35 feet down, with a ditch slicing through it to about 40 feet. I zoomed in on the ditch and spotted fish I couldn't pick out on 1X, but on 4X I got good images of them belly on bottom in the ditch at the edge of the hump. We took turns dragging C-rigs with floating lizards of different colors down the ditch (partner) and along the edge of the hump (me), my partner bringing up one bass about 6 pounds from that bunch, which killed the bite there.

Jim

[fishlikemad]

I guess the first question would be what is the water clarity like.  I have to fish muddy or stained water most of the year (no joke, I fish the Ohio River creeks) and I can catch fish close to the boat.  But if I go to a lake with anything better than stained, I spook them so I have to stay back and make long casts (while trolling a long way in.)  

Now, about nailing down that waypoint.  Use your GPS, by keeping it in one location on your boat, zig-zag back and forth until you find the structure.  Keeping in mind that his GPS may not be as good (or yours) so you may have to look around the location a bit.  

Once you found the location of the structure, mark it, and go fish somewhere else for some hours (considering the water is clear.)  So when you come back (that day or some other day) you will know it's exact location.

Josh

[Garnet]

In my area we fish both stain and clear water. In either situation i zoom my gps to the smallest scale .1/mile and only then do I enter a waypt. In some lakes I gps my boat position on others were I want my bait. I also enter all cal. gps or hand out gps as a 3 didgit # then when I'm there I scale to the .1/mile screen and enter gps and remove the handout.

Even the pos of the antenna from boat to boat makes a Difference.

Garnet

[RoLo]

      by Garnet

i zoom my gps to the smallest scale .1/mile and only then do I enter a waypt.

My mistake, you didn't specify GPS so I presumed you were referring to your sonar.

Okay, that makes perfect sense. I have a Garmin that I can zoom-in until 500 ft,

after which I get the "Overzoom" message where accuracy becomes distorted.

Which is exactly what you said (1/10 mile).

Even the pos of the antenna from boat to boat makes a Difference.

You bet!

If you've done any wreck-fishing in the ocean you quickly find out how exasperating

another skipper's coordinates can be, though they may work fine on his boat,

and vice versa

Roger

[boatnik13]

Hey BLANKED !  Ok I see the depth but how big is the area your fishing? What I mean is > are there any land near by ?  I use gps just to hone in on the area but I strongly use other help such as a range finder and compass for area's surrounded by land or within 800 meters. One more Item I use and could be used in large bays of no land in sight is markers. I lay out markers on my structure and let things calm down then go in and fish them area's that you used your depthfinder on as you may have spooked them  the first time. I use poly foam markers with string and a sinker so I'm on the location and can work it my way. I mark my own waypoints and don't use someone eleses. Gps is a reference and a compass , depthfinder and markers are exactness.

[Guest ouachitabassangler]

Try trusting GPS waypoints more, as even a sloppy one will get you within 20 feet of the spot, while compass sightings on water can't possibly get that close. A well made 10 second waypoint will settle it down to 3-6 feet using 4-5 satellites with 3 in the low horizon. Maybe a theodolite survey instrument can rival a GPS coordinate, as no pocket compass can split a degree. I'm a forester, used a compass for 30 years navigating forests with maps or making maps, pacing steps to get distances, getting maybe a half chain accuracy (33 feet +/-). On the water a compass and shoreline reference points with a map was all we had, which was OK for accuracy within a hundred feet or so, but that system is obsolete now. The problem with that was getting back to a spot lining up two or more compass shots, requiring a lot of moving around until everything matched up. Even with a chain for measuring distance using a compass I've never matched what I've done the last 10 years in the woods with a hand-held GPS. Once on a spot with GPS you can set a proximity alarm that sounds off when the boat wanders a chosen distance from it. I consider markers as final products of GPS tracking, giving me a visual of what I saw on sonar, points of reference for casting across or along a structure.

While at this here, it doesn't matter how far in you are zoomed in map page for making a waypoint. The spot coordinate would be the same. I understand whoever it was was zoomed in on the sonar page, which does make a difference, getting over a specific stump or rock, but even then that isn't all that accurate unless you KNOW the transducer was directly over the object. Zooming in on a stump might be displaying a stump that's in the outer edge of the cone, being as much as 20 feet off in deep water.

Jim

[RoLo]

Not to stray from the original question, the poster doesn't have his own coordinates

so it's a foregone conclusion that he must use another person's coordinates (that's fine).

The compass is out, because whether your following True or Magnetic North

the compass is a crude instrument whose only claim to fame is "reliability".

If I'm offshore and my boat loses all power, I still have my compass however crude.

It is also true that over an offshore wreck in 250 ft of water, the conical accuracy

of my depth sounder leaves much to be desired, especially in a rough sea.

However in the shallow waters that I ply for bass, the depth sounder offers ample accuracy.

A cross-fix can be made without Loran-C or GPS. Before picking up and leaving a newfound sweet-spot,

record the exact depth under the transducer and select "one" 2-object fix that is "perpendicular"

to the depth line (contour line). On your return visit, get on the 2-object fix in deep water

then grab hold of a marker buoy (the flat orange type doesn't completely unwind).

While keeping both objects in alignment, ride-up the slope from deep to shallow water until reaching

your prerecorded depth, which completes the cross-fix. Toss your marker buoy to nail the location.

If there's no strong slope between shallow and deep water, It's Not A Sweet Spot

The above method doesn't require any special equipment, but there are better and more accurate ways

to stick a fix without GPS. With a pair of "bearing binoculars" you can get an LOP (line-of-position)

just about anywhere at all, except in a fog or if you're more than 20 miles offshore and out of sight

of the horizon. Sorry to ramble, but 'location' is the bread-and-butter of fishing, and not the latest lure

or the hottest color for plastic worms.

Roger

[Nick B]

Another thing to consider, is the coordiate format. Make sure that the coordinates he gave you are entered in the same format. That could put you off a little too.

[Ben]

A lot is going to have to do with the GPS.  I've got a three year old Megellan that you couldn't consistantly find a dump truck in a football field with.    You can mark a waypoint and be darn lucky to get within 25 ft one out of three times.

[RoLo]

Another thing to consider, is the coordiate format. Make sure that the coordinates he gave you are entered in the same format. That could put you off a little too.

That's true.

On most GPS units the 'coordinate syntax' is adjustable, where each format provides different accuracy.

Below is noted the difference in accuracy among some of the most common coordinate formats.

I should first point out that you'll notice there is a discrepancy in the placeholder size between

Latitude degrees and Longitude degrees. Since Latitude can never be greater than 90 degrees

from the equator, it has a 2-place degree field (NDD). Longitude however can diverge up to 180 degrees

from the Greenwich Meridian so longitude has a 3-place degree field (WDDD).

COORDINATE SYNTAXES

Order of Descending Accuracy

NDD MM.mmmm WDDD MM.mmmm (1/10,000 minute)

NDD.ddddd WDDD.ddddd (1/6,666 minute)

NDD MM SS.ss WDDD MM SS.ss (1/6,000 minute)

NDD MM.mmm WDDD MM.mmm (1/1,000 minute)

NDD MM SS.s WDDD MM SS.s   (1/600 minute)

NDD.dddd WDDD.dddd (1/166 minute)

Roger

[boatnik13]

To get out of this we need to hear from" BLANK". Blank did say 10-12 ft depth of water  and with a avg. 20deg. cone thats about what > a  3-4 ft. span of coverage of the lake or bay bottom and that it self is like a needle in a haystack to find. also like BEN said > uses a 3 yr old magellan and I to use a magellan. (315) and no W.A.S.S. so getting a 15 meter or better return is ify. I do make lake structure maps that you can re-find the target by boat or ice but my lakes are small (under 4 miles long and 1 mile wide so a compass will aid in this type of water as well as a range finder that do put you within a YD +1-1 up to 800 yards. Getting you on structure is my game but I could never do this in BIG lakes and bays (miles). So I know what some of you are trying to say but this system that I talk is smaller lakes.  I just not sure what BLANK is fishing!  

[blanked]

i have a 3 year old magellan sport trak that has the coord. system as followed

for lat and lon

deg/min.mm

deg/min.mmm  this is the one that i have been using for a primary and secondary

deg/min/sec

and deg.ddddd where should i be set at and why would someone want a less accurate coordinate to begin with??

[Guest ouachitabassangler]

Another issue to keep in mind, especially using waypoints you didn't set, is knowing the offset distance between sonar transducer and GPS antenna. If the antenna is 8 feet away, that stump seen on sonar is waypointed 8 feet off. The total error is represented in a circle with an 8 foot radius, in addition to any offset between target on bottom and center of the sonar cone. The waypoint might be set based on an object on the edge of the 20 degree cone, which could be another 15 foot radius error at 100 feet of depth (cone 33 feet wide on bottom). Total radial error would in that case be up to 23 feet even though the GPS position was highly accurate. So in real practice you would have to survey a surface area with 23 foot radius to get directly over target regardless of GPS position. A remedy for some of that begins with running a few sonar cross sections over a target from different directions, then averaging 3 or more GPS waypoints, and of course having antenna and transducer close together. If making a waypoint for someone tell them your offset.

Jim

[RoLo]

Good point!

What you've decribed is called "parallax" (axial separation).

Another example of parallax is the distance between the rifle bore and the rifle scope.

With GPS, the parallax is exacerbated by the transducer cone, which is to say,

if you approach the same object from opposite directions you will double the parallax.

Roger

[boatnik13]

I like what the post said > because if I drive,walk,boat past a object and do it about 3 times > I get within a few feet of the object and i don't even have WAAS. If i make just one pass and jot down the #'s its going to be off ,up to 45 ft at times. Thats hell in water if your only in 10ft. depth!. So avg. ing is best. I agree.

[scbassin]

WOW & I though marking an X on the side of my boat was high tech.

[Guest ouachitabassangler]

The problem with those X's is they wash off. If you can find it floating around next trip maybe that's the spot?  ;D  If not put it back on.

Jim

[RoLo]

LOL!  ;D