I was asking the Lowrance rep the other day about marking a trail through a stumpy area of the lake so I could get through it a little faster. He strongly suggested that I not depend on GPS for this. I knew GPS had a small error margin but evidently the error margin is a lot bigger than I thought. It seems as though the Department of Defense will not let GPS manufacturers make their products that will get closer than 15 feet of the desired target. He also showed me a place on my unit that will show the error margin in feet (it changes constantly). This is why sometimes I have to look around for my brush pile although I dropped the buoy on top of it (so I thought). Also have to figure in the distance between your receiver and transducer and of course speed. Anyway, thought there might be some of you (like me) that didn't know some of this. Good fishin

I have also noticed that on certain lakes this error margin seems to be more than on other lakes.

I didn't know that, now can you tell me why the fish are always on the other side of the pile I'm fishing?...and they seem to move accordingly.. hahaha

That�s EASY Troy...they are skeered of them King minnows you use!

Did ya notice they are all swimming the same direction?

Used to have this very discussion with a surveyor that was a customer. He used satellite technology, but was a late adopter. He told me that originally surveying technology was around three foot off actual coordinates, so nobody was willing to use it. Then apparently they got it down to a foot off... but if you were willing to register/pay a hefty sum, you could get down to three centimeters off, which is where he got in....he said the technology was capable of exact match, but govt refused to allow such accuracy due to national security concerns. The part I thought was so interesting was how he had to safeguard his equipment, evidently due to the accuracy of the equipment capabilities.

Any rate good read on an interesting topic....although I always thought the accuracy was three feet off.

That is the dumbest thing I have ever heard!!!!! .... Probably true, BUT DUMB!! Our elected officials and the morons they appoint to positions of power come up with the dumbest things!
If somebody was gonna drop a bomb using an HSD9, I doubt 15' would make much difference!

Haha, my exact thoughts too but I'm sure there are other reasons that we'll never know about.

YEAH, They didn't get their pockets lined for allowing exact location!!!! .... Probably wanted more kickback than it was worth!

Close enough is only works with horseshoes and hand grenades

It actually effects all GPS, not just marine units.

The Lowrance representative certainly gave you good advice. But to be clear, inaccuracies, called User Range Error (URE) result from several factors, none of which is the U.S. Department of Defense. That practice, known as Selective Availability, ended in 2000.

Here's a short overview if you're interested:

https://www.gps.gov/systems/gps/performance/accuracy/

Thanks for the link. That was an interesting read. We did discuss the factors that can cause variations in the readings but the reps did mention the DOD restricting the accuracy of the gps reading. I wonder if they don't know about the ending of the selective availability. Anyway, as long as I can find my brush piles I'm a happy fisherman and I'll keep idling through the stumps.

There is a spot on my lake that I am having a tough time to mark. It is close to the dam.
Do you think there could be something at play here ? The spot I want is on a drop off,
so it is obvious if you are off by a little. I have dropped about a half dozen waypoints,
none seem to land where I want to be. I've never had this happen anywhere else on the lake.


MO

If you use an external gps source for a Lowrance unit (point 1 gps puck) you should land right on top of your brush every time. I haven't had the same problem Bush Hog and I run the point 1 gps on mine. Not sure if this helps or not, just throwing it out there.