BigBendFishing.Net

Went out today and hit some new holes that I have put together from here there and yunder. Covered a lot of water and unfortunately didn't do real well. I talked to folks on four different boats at the ramp when I was pulling out, and every one said they had a bad day too. One feller said that it was the worst day he had ever had, but then another guy said that they had been grouper fishing all day and had not caught anything but one grunt, so I'm not sure about the reliability of my info.

Hitting these new holes, I got to wondering about something, and maybe somebody can tell me. I am positive that my GPS will return me very close to the same point every time, but is there some difference between each GPS unit? I went to a number today that was given to me by a reliable source and couldn't find anything on my bottom machine, but a little over a tenth of a mile away there was two boats that were catching fish. That was not so weird until I hit a few more holes from the same source circled around all over it, but my bottom machine never showed anything worth fooling with. I'm just wondering if there could be some offset or something.

Wound up with 2 good reds and a box full of grunts that were originally intended to be bait, but now are in there being fried in the kitchen. I'm not Korean, but I'm eating the bait anyway.

Best bet is it was a datum shift. Some folks have points in NAD 27 and some in NAD83 (WGS84 will map the same as NAD 83) The difference in our part of the world is 200 meters. You can shift those points with some free software. The points that are posted on the OAR site are a mix I have found, depends on where they came from and how old they are.

Sharkie:

I doubt that it is as complicated as a datum (but hey, could be!) shift.

My opinion is, that it is nothing more than variations in GPS equipment and circumstances over time. Remember, up until a couple of years ago, the military degraded the GPS signal (called it selective availability) on a random basis, so that accuracy might vary from 30-150', or more. If the L/L for a spot was stored when the variability was high, you have a location that is off the mark. Then, you add in your current receiver and how it is doing on a particular day and you could be way off from a number someone gives you or you find on the charts.

If I store my own L/Ls with my GPS receiver with differential, I KNOW I can return to that number, within 15 feet, but given anyone else's number, you never can tell. Sometimes, a location will be given that indicates the number was stored with differential, and that will most likely be closer to right on.

These days, most folks buy a GPS with WAAS, which will give an incredibly accurate location, as long as the WAAS satellite (only one in operation) is in view and not blocked by the console or a tower, or something. If the WAAS satellite is not in use, then you are back to 25-30' or so, which is still pretty good.

When "given" a number, I go to the spot, toss a buoy, and begin a search pattern for bottom. Many times, I find the spot (or what I think is the spot) 50-100' away from the buoy. Then I mark the real spot with my own GPS and I am good to go.

EJ

I agree with EddieJoe on the type of equipment you are using. If you point was in a different datum, you would have seen the other boat either north or south of you as the error is north to south. Always is a good idea to check the datum when entering points from a chart though.