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Waypoint Averaging Oregon 450t Help needed to this procedure

#1 User is offline   polakis 

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  Posted 07 November 2010 - 04:21 AM

Hi fellows,
i am a happy owner of the Oregon 450t and i can say, it is a great device. I am on my way posting my first cache and i would like some help on using correctly the 'waypoint averaging tool' of 450t.

When i want to mark a new waypoint for a cache, do i go directly to the waypoint averaging tool, or first mark the spot and then go to the tool for corrections. I made some tries and i really cannot understand if the averaged calculations saved on the first mark, because the spot has not not been fixed (in accuracy speaking) and had to reposition it.

In one phrase, let's say you need to get an accurate mark, what steps do you follow with the Oregon 450t in order to get advantage to the device capabilities?

Looking forward for your help!!

Thank you and happy geocaching :P :blink:

#2 User is offline   splashy 

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Posted 07 November 2010 - 05:04 AM

http://garminoregon.wikispaces.com/Waypoin...Garmin%20Oregon?

W14

#3 User is offline   dfx 

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Posted 07 November 2010 - 05:05 AM

just go directly to the averaging tool and create a new waypoint there. let it do its thing until the bar reaches 100% and hit the save button. that's pretty much it. if you want to rename the waypoint afterwards, you can do it through the waypoint manager.

the additional averaging towards an already existing waypoint is useful if you want to take multiple readings over several days. it's gonna get more accurate over time, but so far all my single reading averaged waypoints have been accurate enough for all purposes.

#4 User is offline   polakis 

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Posted 07 November 2010 - 06:45 AM

View Postdfx, on Nov 7 2010, 05:05 AM, said:

just go directly to the averaging tool and create a new waypoint there. let it do its thing until the bar reaches 100% and hit the save button. that's pretty much it. if you want to rename the waypoint afterwards, you can do it through the waypoint manager.

the additional averaging towards an already existing waypoint is useful if you want to take multiple readings over several days. it's gonna get more accurate over time, but so far all my single reading averaged waypoints have been accurate enough for all purposes.


Thank you for the usefull info both of you provided.

to dfx:
i have done this, gone directly to averaging and marked the spot after the 100% bar was visible and i left it a little bit more. When i returned back to check the spot, i noticed that the accuracy was not so good. I repositioned the waypoint and then it was more accurate.

Do you have any logical explanation for that, or it may happen some times?

Thank you in advance :P

#5 User is offline   bobandrobin 

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Posted 07 November 2010 - 07:07 AM

View Postpolakis, on Nov 7 2010, 09:45 AM, said:

View Postdfx, on Nov 7 2010, 05:05 AM, said:

just go directly to the averaging tool and create a new waypoint there. let it do its thing until the bar reaches 100% and hit the save button. that's pretty much it. if you want to rename the waypoint afterwards, you can do it through the waypoint manager.

the additional averaging towards an already existing waypoint is useful if you want to take multiple readings over several days. it's gonna get more accurate over time, but so far all my single reading averaged waypoints have been accurate enough for all purposes.


Thank you for the usefull info both of you provided.

to dfx:
i have done this, gone directly to averaging and marked the spot after the 100% bar was visible and i left it a little bit more. When i returned back to check the spot, i noticed that the accuracy was not so good. I repositioned the waypoint and then it was more accurate.

Do you have any logical explanation for that, or it may happen some times?

Thank you in advance :P


If I may...

Don't expect the gps to bring you back to the exact spot you marked. You may get lucky and have that result but don't expect pinpoint accuracy. A 30' radius is an acceptable margin of error on a good day.

#6 User is offline   ecanderson 

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Posted 07 November 2010 - 08:30 AM

After some 3200+ finds, I would conclude that anything placed and found with decent equipment and averaged properly that turns into a 30' radius (60' diameter circle) is a truly "bad hair day" for satellites. More often, it's the result of taking a "snap" single reading and posting that instead of doing it right. That kind of error isn't "an acceptable margin of error on a good day". Might have been once, but now you should expect no worse than half that on a good day.

Do expect some variation. If you find that your averages are causing differences of more than +/- 0.002 minutes (that would be a total of about +/- 12' N/S and about +/- 8' E/W from GZ), it's not a good day. So an ellipse/oval of about 16 wide by 24 tall is the most you should tolerate with a good GPS. If you're outside that +/- 0.002, try again at a different time.

There CAN be days and times of days where the alignment of the satellites in the sky produces a better or worse level of accuracy. Having them spaced out nicely in a circular pattern in the sky would be ideal, but it never happens.

#7 User is offline   dfx 

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Posted 07 November 2010 - 02:12 PM

View Postpolakis, on Nov 7 2010, 09:45 AM, said:

i have done this, gone directly to averaging and marked the spot after the 100% bar was visible and i left it a little bit more. When i returned back to check the spot, i noticed that the accuracy was not so good. I repositioned the waypoint and then it was more accurate.

Do you have any logical explanation for that, or it may happen some times?

how do you know that the accuracy wasn't so good?

GPS will never give you exactly the same coordinates at the same location, it will always vary to a certain degree. that's the whole point of averaging: to eliminate the variance, or rather reduce its impact.

the oregon will tell a certain "GPS accuracy" value, which is an estimate as to how accurate you can expect the current coord reading to be. it's not a guarantee, so it can be better than that or can also be worse. generally, if it shows you a distance to the waypoint of less than the accuracy reading most of the time, then the coords should be good.

averaging itself also gives you an indication about accuracy, namely the "distance adjusted" value it shows you after you hit the save button. basically it's the amount of variance the oregon has encountered during the averaging process. the lower the value is, the more accurate you can expect the coords to be, and the better current reception conditions. in the best cases, you'll get 1 meter or very rarely even 0, and under those conditions you should be able to reliably get back to at least 1-2 meters distance to the waypoint. under bad conditions you can get anything over 7 meters or so - don't expect any reliably reproducable results under those conditions.

#8 User is offline   polakis 

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Posted 07 November 2010 - 02:31 PM

View Postdfx, on Nov 7 2010, 02:12 PM, said:

View Postpolakis, on Nov 7 2010, 09:45 AM, said:

i have done this, gone directly to averaging and marked the spot after the 100% bar was visible and i left it a little bit more. When i returned back to check the spot, i noticed that the accuracy was not so good. I repositioned the waypoint and then it was more accurate.

Do you have any logical explanation for that, or it may happen some times?

how do you know that the accuracy wasn't so good?

GPS will never give you exactly the same coordinates at the same location, it will always vary to a certain degree. that's the whole point of averaging: to eliminate the variance, or rather reduce its impact.
[size=3]
the oregon will tell a certain "GPS accuracy" value, which is an estimate as to how accurate you can expect the current coord reading to be. it's not a guarantee, so it can be better than that or can also be worse. generally, if it shows you a distance to the waypoint of less than the accuracy reading most of the time, then the coords should be good.

averaging itself also gives you an indication about accuracy, namely the "distance adjusted" value it shows you after you hit the save button. basically it's the amount of variance the oregon has encountered during the averaging process. the lower the value is, the more accurate you can expect the coords to be, and the better current reception conditions. in the best cases, you'll get 1 meter or very rarely even 0, and under those conditions you should be able to reliably get back to at least 1-2 meters distance to the waypoint. under bad conditions you can get anything over 7 meters or so - don't expect any reliably reproducable results under those conditions.


I see, this seems logical. So i will take a new spot with waypoint averaging function, leave enough time even after 100% bar is complete and that's it.
Thank you very much for your advice. It was very useful.

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