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croixflats

GPS how close do you get to the origanal way point

26 posts in this topic

I'm not up to speed on the GPS. Didnt it use to be the gps would only get you close to where you wanted to go. I was wondering if they changed that now and how close you realy get to that origanal way point.

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between 12 and 30 feet most of the time. most brands tell you what the accuracy is at any given time.

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My lowrance units say I am within 11 feet of the original target. Close enough in my book.

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Thanks for the info 11 ft to 30 ft is close enough. For awhile there I think the accuracy was regulated. That was a while ago.

Even with a marker buoy it is hard to get that boat on the same spot sometimes. 11ft prety darn good

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The gov't regulates GPS so they are not as accurate. Just makes em uneasy that the public can get to within a foot or two of a waypoint!

If you pay a few grand you can get a subscription that'll get you within a meter, other than that 12-15 feet is dam good.

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GPS accuracy is a very complicated issue. Much of it depends on the current satelite coverage and the quality and age of your unit. Generally you can expect your current position to be within a few meters, but that usually doesn't matter for us fisherman. Often times we use the GPS to mark spots (way points) so that we can return to them later. This is where it gets really strange. All GPS errors can "double up" if you store a position, then attempt to relocate it later with GPS. This is because the error when a location is marked can add to GPS errors while re-locating the mark. Let's say you mark that sunken log on a particular structure. Chances are there was a small error when you pushed the waypoint button. Now, you come back the next day and try to find it using the gps. You might be 100 feet or more from it because of the variables causing today's inaccuracies. Seldom will you ever be able to exactly repeat a location, but usually you get close enough. When I mark a waypoint, I always note the depth that I am at. That way I can usually find my spot with pretty good accuracy. especially on drop offs.

I fish a pretty good sized lake and many of my spots are out in the middle of "no-where". GPS is a must for returning to the hot spots.

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Good post Maverick. Many people think their GPS is dead-on.

You will find your GPS is also more accurate at certain times then others.

Another issue is if you are using a hand held unit, like a H2Oc with a Navionics chip, you can only zoom in to 1/8 mile. Not very detailed at that range.

Still, I never fish with out one any more. Second best electronic tool to have in the boat besides the locator.

- Wish

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Thanks Wish,

A fun thing you can try with a hand held is to go to the middle of your yard that is pretty much unobstructed to the sky. Set down a pail or something that will not move. While sitting on the pail punch in a waypoint. Now wait an hour or two and go back to the area. Walk with you GPS until it shows the exact longitude and latitude that your waypoint indicates. Note how far from the pail you are and that will start to give you an idea of the accuracy. Do it a number of times and you will see that different times of the day and other things that effect the view to the sky will impact the accuracy. You could even plot it out on graph paper, but now we are getting a little obsessed with the whole thing.

I agree, I never fish without one either. Recently my Lowrance 3500c stopped working. I immediately mounted my hand held in the boat until I could get the Lowarance replaced.

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I have found that having 2 gps plotters with my waypoints marked is very accurate.Puts me right on top of a few narrow sand bars every time.

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I've used mine aginst others geocaching,Mine is a 1995 model always within 10 ft or less.When I get coords from someone I get right on spot.My full zoom is 100 ft,A new h2o is 1/8 mile??? 660ft?? thats a reason to keep my Magellan Meridian.

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It may only allow you to zoom down so far, but the GPS will show your distance in feet from the waypoint so the zoom factor really isn't an issue.

Using the digital readout is the best way to get right back to your mark, since trying to put a fat cursor on a fat waypoint icon is hardly ideal.

Saying that you're within 10' isn't quite accurate. My H2O will say the same thing when I'm approaching a waypoint, but with the GPS error you're actually still 15' or more from that mark in any given direction. I'm guessing that a circa 1995 model doesn't have WAAS, so it's pretty safe to say it's expected position error is much greater than that. My first GPS unit was slightly newer than that and was lucky if it was 40' on the best days. I suppose that it is possible that the error of the geocache waypoint may have canceled the error of the hand held and just got lucky.

We have a Trimble unit at work that will go sub-meter accuracy, but I can't find the slot to load my Lakemaster chip. grin

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It would appear that my Garmin handheld with WAAS enabled certainly outperforms the H2O when it comes to accuracy and detail. First, it is quite common for my level of accuracy to be within 6 to 7 feet. I have experienced as good as 5 feet but that has proven to be rare. As far as zoom, I can zoom to a 20 foot scale. Much higher resolution than 1/8th mile.

Bob

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My Garmin sure seems to be much more accurate than my H20c. The maps are better on the Lowrance, but that's about all.

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Interesting. Have you Garmin guys seen the new "Oregon" touch-screen units? Not sure how well they work with gloves, probably as good as the Lowrance with the small buttons. smile

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I'll tell you what I did. I marked a spot with my GPS and threw out a marker bouy and then I went several miles away and followed my GPS "pointer" back to the waypoint. I did not look up to see where I was at I just followed the "pointer" and when it said I was there I looked up and the bouy was right next to the boat. I was up to Lake Vermillion several weeks ago (stayed in Pikes Bay) and there was an area about 8 miles away that I wanted to fish. I took a map and loaded 5 or 6 waypoints into my GPS and just follwed it to where I wanted to fish. It worked really slick and believe me I am no computer wizard. I have a Garmin 76 that is about 5 years old and I like it.

I talked to a fellow who had a GPS built into his fish finder and his even showed where the rock hazards were. I am going to upgrade someday and it will definately be a similiar unit.

Good Fishing!!!!!!!!!!!!!

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My Magellan is WAAS enabled and geocaching is using the unit to pinpoint objects anywhere someone posts a object hidden.So I'm going by coords off a post online, enter into my unit and start,only time I lose my focus point is in heavy treed areas,On the water I'm most always on spot and 10 ft. on open water is easy.Never really counted but on water I believe I'm receiving 6-8 sats.+ WAAS horizon reception

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So you must have a 2005 model, not a 1995 model? I believe WAAS didn't come online until the past 1/2 dozen years or so.

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Please note that my post says "with the Navionics chip" it only zooms to 1/8 mile. It is much closer with a Lakemaster chip.

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You can already have that capability on Vermillion, Capt. Check out Garmin's HSOforum and look for their MNLakemaster software. Vermillion is contoured to navigational quality in 3' increments along with I believe over 60 of Minnesota's most popular lakes.

Bob

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Limit its 1995. I downloaded one upgrade the only one provided Since and it was WAAS back then I believe.Look it up on Magellan site.Its under archived units,At the time it was the top of the line unit,it went obsolete 2 yrs later.Its a Magellan (MerridianGPS)

Out this morn I received 10 sats. and WAAS 27 & ???

If ya go to the site you'll see this model was discontinued in 1995

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Be careful when using Estimated Position Error (EPE) values listed on GPS units to determine how far "off" you might be from any location.

EPE can be calculated a number of ways, and depending on the algorithm used, you may be more than 2X the listed value "off." Positional error is determined using Horizontal Dillution of Precision (HDOP), a measure of the visible satelitte's geometric accuracy, and User Range Error (URE), which is a catch-all group of errors from clock timing to atmospheric irregularities. To the best of my knowledge, URE is estimated average from ALL GPS satellites (24+) orbiting the earth, NOT ONLY THE ONES YOUR GPS IS UTILIZING.

In other words, the 6-10 satellites in your viewing area may be exhibiting quite a bit more OR less URE than the total satellite average, throwing off your values.

Take home message - The lower the number the better......kind of? smile

Joel

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Isn't that where WAAS comes into play? It time-corrects for the delay in receiving the GPS satellite signals.

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To answer the original post. Today's GPS units will get you within 3 meters. When in times of war the military scrambles the signal to make the GPS less accurate. (A prior post kinda elluded to this). However, there is a seperate antenna one can purchase that unscrambes this signal but it's way to expensive for the average Joe and frankly not worth it.

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