In a previous post I mentioned having trouble getting on waypointed submerged wood when running my trolling motor as the map would become disoriented. The comment was made that the gps has trouble finding position when you are moving slowly and I had to be moving with the trolling motor on high to get accurate position.

I then got to asking myself how accurate it was to run over something while fishing along slowly and punch in a waypoint.
Are these waypoints accurate?

"...the gps has trouble finding position when you are moving slowly and I had to be moving with the trolling motor on high to get accurate position."

This is not exactly correct - the map orientation depends on what direction you're facing, but GPS doesn't have a compass and speedometer; it calculates your direction and speed based on movement. If you're moving slowly or not at all, and/or changing direction often, it won't know for sure which way you're facing.

The position in terms of latitude and longitude should be precise.

First off you can be off by up to 30 feet depending on the GPS and the reception conditions.

If your GPS is set to change the maps orientation to always point forward, learn how to turn that off. It's nice when your moving at speed and going place to place but a nightmare for fine tuning your location in on a spot.

Lock up to North, and keep zooming in on the map as you get closer to the waypoint. With a little practice you should be able to use this to get on the spot as accurately as the conditions will allow.

Also remember that the Antenea placement will make a difference as to how close to a spot you can get too. The GPS is putting the Antenea on the same spot, not necessarily the boat. For instance if the antenna is on the back of the boat and the FF is on the front, and it's 20' between the two you could be 20' off the spot in any direction. The only time things will be exactly the same is when the boat is oriented the same direction as when you marked the spot.

Does the epe on a lowrance provide the potential error from a certain point? Or am i using this all wrong?

Michial, mine trails through the small boat cut on the north Jetty were off by almost 61 feet last weekend according to the " find the distance tool". Are your trails supposed to be just as accurate as waypoints?

Several factors at play here.

How many satellites were you tracking?

Were you locked into WAAS?

What was the Estimated accuracy?

I use basic handheld GPS a lot at work along side high dollar Trimble RTK differential survey grade systems. After lots of testing and numerous day to day observations I have found that the handheld units, with WAAS and plenty of satellites are within 10 feet 95% of the time. This is for X & Y only. Elevation is horrible on the handheld units.

When you get large errors you likely are not in WAAS, not seeing many satellites, etc.

If you are just punching in once to save a waypoint then it just takes a reading. With the Lorance they have a averging position and I let it take like 75 readings and it is right on. It even tells you this is by far the most accurate way to set a way point.
Johnny

Your tracks are only as accurate as your GPS is, and it all depends on the number of satelites... More satelites = more accurate. Some good things to do to help is try to mount your receiver as high in the boat and as flat as possible, try to eliminate as many items as possible that shade the receiver from the sky. Make sure there's no kinks in the wiring for the receiver and probably doesn't hurt to make sure your getting good voltage and amperage to your unit.

Like someone said, mark the same location several times over a couple of seconds and you will get the most accurate position from the average.

OR you just accept that it will not place you on a dime every time, and use it to get you within a coin toss of your location. Your "find the distance tool" if you are refering to the ability to move a cursor to a spot is probably off so much because it's hart to put the cursor exacly where you want it. Having a GPS off 30 feet is difficult to do if you even remotely have good reception, 60' would need low signal strength AND small numbers of satelites at the same tim.

As for WAAS, if you withing the WAAS station's operating range it will improve your accuracy, but be careful, it's possible that WAAS can also throw you off much more.

WAAS is a fixed station on the ground with a known lat/lon that constantly reads it's position from the satelites and then broadcasts an error correction, but they are only accurate for a small distance from the WAAS station. I personally leave WAAS turned off, I have seen it throw positions off by as much as 125' before.

WAAS was first used by surveyors to get accurate readings, but even they only used it to find starting markers, then they went with the old fashioned methods of measuring out from known points. It's not used in the IFR GPS's for planes, and most IFR or commercial airports will have WAAS stations on them, also inside large metros like dallas your fine too, but get out in the country on the edge fo their broadcasting ranges and your going to see major errors.