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Melismobile
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Joined: Apr 14, 2005
Posts: 77
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 Posted: Fri Apr 15, 2005 12:22 pm Post subject: Garmin Etrex accuracy |
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I bought this unit primarily to locate specific points eg rocks with fish under them. But I find it is not really accurate enough. Is there a patch that will increase its accuracy ?
Mel |
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missing_user
Joined: Aug 30, 2008
Posts: -7
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| Posted: Fri Apr 15, 2005 1:49 pm Post subject: |
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I have two Garmin units,eMap and iQue, and the best accuracy I have noted is 16 feet in the UK!
What accuracy are you getting, and what accuracy are you expecting? |
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Melismobile
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Joined: Apr 14, 2005
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| Posted: Fri Apr 15, 2005 2:22 pm Post subject: |
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Well 16 sq foot is an aweful lot of rocks on a beach 8O I guess minimum 1m square would be nice
Mel |
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missing_user
Joined: Aug 30, 2008
Posts: -7
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| Posted: Fri Apr 15, 2005 2:32 pm Post subject: |
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| Only the Military people have that accuracy as far as I know. |
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Melismobile
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Joined: Apr 14, 2005
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| Posted: Fri Apr 15, 2005 2:55 pm Post subject: |
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I was told it was possible to get a better accuracy Oh well waste of space then 
Mel |
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missing_user
Joined: Aug 30, 2008
Posts: -7
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| Posted: Fri Apr 15, 2005 3:03 pm Post subject: |
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| Just been told by a friend that Surveying Organisations/Local Government Planning may have equipment more accurate for your work! |
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Skippy
Pocket GPS Verifier
Joined: 24/06/2003 00:22:12
Posts: 2946
Location: Escaped to the Antipodies! 36.83°S 174.75°E
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| Posted: Fri Apr 15, 2005 3:04 pm Post subject: Re: Garmin Etrex accuracy |
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| Melismobile wrote: | | I bought this unit primarily to locate specific points eg rocks with fish under them. But I find it is not really accurate enough. |
A couple of things to try:
Switch on WAAS which will give you a more accurate fix if you can see the WAAS satellite. You will know if you do because you will see the letter "D" appear in the GPS status screen and it will say "3D Differential Fix". This is supposed to improve the accuracy to better than 3 meters.
Some Garmins also have an "averaging" feature. Your position acutally jumps around a bit even when you are standing still. On my GPS-V you can mark a waypoint as an average location measured over a minute or two which may give a more accurate reading.
If you mark a waypoint and then come back to it within a few hours, then you will probably get a fairly accurate pointer back to where you were. If you come back days later then you may find that the waypoint has shifted a fair bit.
You can get very accurate survey grade GPS systems (sub centimeter) but these are quite expensive, bulky and cumbersome to use.
The bottom line is that, in the real world, it doesn't really get a whole lot better than what you already have. 
_________________
Gone fishing! |
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Melismobile
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Joined: Apr 14, 2005
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| Posted: Fri Apr 15, 2005 7:43 pm Post subject: |
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Thanks I'll try the suggestions. Taking more equipment (ie biger survay stuff) is not really a viable option, as there are other things I have to carry as well
Yes I return days later, as I'm studying homing behaviour and trying a non invasive methodology. I was hoping to lessen the marks on the rocks if I could get the GPS more accurate.
Mel |
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oddsock
Pocket GPS Verifier
Joined: May 01, 2004
Posts: 706
Location: Monmouthshire
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| Posted: Fri Apr 15, 2005 10:19 pm Post subject: |
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| Melismobile wrote: | Thanks I'll try the suggestions. Taking more equipment (ie biger survay stuff) is not really a viable option, as there are other things I have to carry as well
Yes I return days later, as I'm studying homing behaviour and trying a non invasive methodology. I was hoping to lessen the marks on the rocks if I could get the GPS more accurate.
Mel |
 Would digital photo's be out of the question Maybe you could take one of the rock from your waypoint and then when you go back to the spot you could refer to the print/review screen to make the ID !
Dave |
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Melismobile
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Joined: Apr 14, 2005
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| Posted: Fri Apr 15, 2005 11:45 pm Post subject: |
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| oddsock wrote: | Would digital photo's be out of the question Maybe you could take one of the rock from your waypoint and then when you go back to the spot you could refer to the print/review screen to make the ID !
Dave |
Yes I do that too. And photos of the rocks lined up with a fixed point or 3, eg lighthouse, visible house, which won't move (I hope)
It helps if you get within a metre or two, but not much further away which is where I hoped the GPS would come in. Lost a total of 4 rocks last survay, which wasn't too bad, but it is frustrating
It is surprising how different a rock can look from a slightly different angle, 2D to 3D fails quite a bit. So I'm not sure how many photos I'd need to make a really good ID if I approched it slightly incorrectly ;)
I'm using digital photos as fish identification rather than physically marking them, which has been great.
Mel |
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