Geko accuracy!!

Discussion about software such as GSAK, OziExplorer etc, as well as all things hardware, GPSrs, laptops, PDAs, paperless caching, cables etc
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VKC1SR
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Geko accuracy!!

Post by VKC1SR » 17 September 04 12:06 am

Just a query as to what sort of accuracy people get with their Geko!??

I've got a Geko 201 and the best that I have seen the accuracy is 3M

Got a mate with a Magellan 2000XL and his EPE gets down to 0M

Doesn't make any difference when we are caching as we can still find what we are after.

I'm in Victoria!!
Just for interest sake!!

Nich
VKC1SR

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CraigRat
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Post by CraigRat » 17 September 04 1:41 am

The usual formy Geko201 is usually 4-5m which works out ok. Just gotta do the 'Garmin Spiral' a bit when you get close to GZ..<p> I've had 8-9 sats in view on top of Mt Barrow in tassie and still 4m was the best I can seem to get.<p>
A mate just got a garmin GPS76 the other day, and to me it seems like the Geko is a fair bit quicker to get a lock and to track. <p>Hopefully taking him out for his first taste of caching on sat.....<p>My 2 cents...

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Papa Bear_Left
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Post by Papa Bear_Left » 17 September 04 8:35 am

We use an eTrex and a Meridian Green and find that the eTrex is usually quicker to settle down but a little more... optimistic in its estimated error.

The Magellan takes a little while to zero in (it auto-averages) but generally ends up closer to the mark.

I've never got better than 4m accuracy in Oz or NZ, except when using a differential GPS system, but I was routinely getting 2 and 3m EPEs in the US, where the WAAS system is effective. Nice not to have to search too much area where there's poison oak!

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Webguy
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Post by Webguy » 17 September 04 9:57 am

When we put out Wall 2 Wall views #1 - Rigby, we had between 9 and 11 birds depending on where we were on the hill and best we had was 4mtrs.

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Post by Mind Socket » 17 September 04 10:46 am

I expect the Magellan and Garmin simply calculate this number differently. I don't think I've ever had my eTrex estimate less than 3m. As you say, it doesn't matter if you can triangulate to the territory and track down the tupperware treasure trove. :p

- Rog

Mix
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Post by Mix » 17 September 04 10:59 am

for real accurate caches try this
<br><br>
Image
<br><br>
AUSPOS
Submit 24 hours of GPS data as a RINEX file to AUSPOSÂ’s Online GPS Processing Service, and within 15 minutes you will receive geodetic coordinates accurate to two centimetres, for any location in the world.

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Post by Mind Socket » 17 September 04 11:02 am

Awesome!!! Linky? Free? RINEX?

- R

sikma
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Post by sikma » 17 September 04 12:52 pm

For AUSPOS check out
<br />
http://www.ga.gov.au/nmd/geodesy/
<br /> linking to
<br />
http://www.ga.gov.au/nmd/geodesy/sgc/wwwgps/

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Papa Bear_Left
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Post by Papa Bear_Left » 17 September 04 2:05 pm

Oooh! A few cm accuracy!

OK, it's not terribly convenient to sit your GPS and a data-collection device (PDA with a big battery? Laptop with a REAL big battery?) out in the bush for 24 hours to collect the data, but maybe 2-3 hours is achievable for special occasions.

For setting caches, I think I'll be satisfied with DGPSoIP, as per this thread.

For getting a really accurate fix on your front door, though, this sounds great.

(I think I have to try it, just because it's there!)

VKC1SR
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Post by VKC1SR » 17 September 04 3:28 pm

Thanks for the comments.
I was just a bit unsure about the accuracy but I'm quite happy now seeing as it appears to be behaving normally.

I leave for NZ tomorrow for 2 weeks cruising the South Island in a motor home. I'll just chuck one of those AUSPOS things on the roof and away we go!!
Already got a few caches printed out ready to be logged.
It'll be nice to have some international caches under the belt.
Had to find nice scenic ones so that "she who must be obeyed" will let me play.

See ya all in a couple of weeks!!

Nich
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Papa Bear_Left
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Post by Papa Bear_Left » 17 September 04 4:02 pm

VKC1SR wrote:I leave for NZ tomorrow for 2 weeks cruising the South Island in a motor home.
Already got a few caches printed out ready to be logged.
While you're passing throguh Christchurch, you should pause at the one I linked to above (unless it's business hours), just to test the spot accuracy of your Geko.

I reckon it's the most accurate cache coord in ChCh, if not NZ!

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EcoTeam
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Re: Geko accuracy!!

Post by EcoTeam » 17 September 04 8:11 pm

VKC1SR wrote:Just a query as to what sort of accuracy people get with their Geko!??

I've got a Geko 201 and the best that I have seen the accuracy is 3M

Got a mate with a Magellan 2000XL and his EPE gets down to 0M

Doesn't make any difference when we are caching as we can still find what we are after.

I'm in Victoria!!
Just for interest sake!!

Nich
VKC1SR
Don't take the EPE at face value, it's only an estimate of the position error based on signal quality and other factors. It is not an absolute figure. Many people don't understand this.
Just becuase your GPSr says 3m EPE does not necessarily mean you within 3m of the absolute displayed position, in fact it's most likely to be significantly more than that.
Regular 12 channel receivers without any of the additional technology like DGPS or WAAS are only good to approximately 10-15m at best *at any instant in time*, regardless of what your EPE says. DGPS gets under 5m, and WAAS is slightly better than that, again, at any instant in time.
Of course, we all know Geocachers achieve typically 5m with a standard GPSr, but that's only after averaging and a bit of hunting back and forth.
You can see the real error effect in action when you are approaching a cache and your GPSr may "overshoot" by 20m or more.

Also, some receivers will quote EPE as a diameter instead of the more common radius, so the value displayed will need to halved. I believe the Magellen Meridian does this.

EcoDave :)

Geof
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Post by Geof » 20 September 04 9:36 pm

The best mine has ever said is 4m. I'v had a 6m EPE that was 60 meters out and a 4m EPE that was 75cm out.

I think they (Geko) may have some software glitches as mine has a maximum speed reading of 3368kmph and the same day it said I was 1400 km to GZ when I was about 1km away. A restart fixed it.

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Post by Kerry » 20 September 04 10:16 pm

Even though there are some handhelds that RINEX can be recorded from, as far as AUSPOS is concerned it's no good as AUSPOS will only process dual frequency data, so don't get over excited.

As for what a Geko or a Magellan or whatever says the "estimated error" is, it really wouldn't know as the unit doesn't know exactly where it is anyway. EPE (Estimated Position Error) is not "accuracy"

Cheers, Kerry.

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Post by Mr Darcy » 22 September 04 12:21 am

The best mine has ever said is 4m. I'v had a 6m EPE that was 60 meters out and a 4m EPE that was 75cm out.
But don't forget that you are comparing to someone elses GPS (unless you are using a fixed and known mark like Greenwich England), so all you are really saying is that you are 60m/75cm different from what that person was reading the day they set the cache. You could be out. (s)He could be out, or more likely both.

My 2c Mr Darcy

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