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Old 30-08-2015, 07:13   #76
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Join Date: Jun 2007
Location: SW Florida
Boat: FP Belize, 43' - Dot Dun
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Re: GPS accuracy

Quote:
Originally Posted by zeehag View Post
all i am able to do is roll on deck laughing my ass off at this insensitive and off base remark. i have posted much proof of this along the path of my adventures. might wanna look it up in search feature.
i am excited and blissfully happy that folks who are not reading the information on my gps and various other machines run features and placement by same is only subject to YOUR numbers, what happens in real world is apparently a lot different than what your arbitrary numbers choose to show.
that is problem with numbers.
they FAIL to show anything other than what the collector of data desires to prove. folks choose to skew data and choose to listen to false information, yet, when it comes to real world use, there is denial and balderdash and arguments.
ok
you win. there is no deviation and no inaccuracy in gps. none programmed in and no jamming and no anything to befoul your happy snotty yotty planning in virtual time.
i hope you land on a shoal you are not able to exit due to your insistence that your gps is totally perfectly accurate.
i presume you use yours in a vacuum.

i know all about charts admiralty and otherwise, as the newest info on charts states 1865 or thereabouts.
yes i read fine print and i have been sailing since age 7, which, to you, is forever, as i am OLD. i even know how to use a proper lead line and knot line.
rodlmffao.
feet not fathoms inland fool.
Zee,

I've never doubted your observations. I've only disagreed with the explanations you give to support what you've observed.

Your refusal to accept that putting a blinking dot on a map involves 2 distinct processes that are managed by different entities is at the heart of the issue. I claim it's mapping errors, you claim the Gov't is purposely skewing your GPS in an attempt to force you into a shoal.

FWIW, I would never wish that someone hit a shoal, and I'm surprised any sailor would wish such a thing on someone.

I think this discussion has run it's course.
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Old 29-04-2020, 04:09   #77
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Re: GPS accuracy

A new GPS device is available now with accuracy in the millimeter range:
https://www.sparkfun.com/products/16481
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Old 29-04-2020, 05:16   #78
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Re: GPS accuracy

Quote:
Originally Posted by CarCode View Post
A new GPS device is available now with accuracy in the millimeter range:
https://www.sparkfun.com/products/16481
Nothing new there. Its GPS-RTK, not GPS.

RTK has been in use for at least 20 years to my knowledge.. Great for detaled survey work - useless for navigation.

Real Time Kinematic is a technique used to increase the accuracy of GPS signals by using a fixed base station which wirelessly sends out corrections to a moving receiver. By utilising these corrections, the GPS engine can fix the position of the antenna to within 1 - 2cm.

You need to be within about 10 NM of the base station to pick up its signals.

And your link says "Horizontal Position Accuracy: " - "0.010m" which is not "in the millimeter range"
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Old 29-04-2020, 06:25   #79
bcn
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Re: GPS accuracy

For purposes that do not need mm precision (but 2-3cm) differential corrections from a station 20nm away are still acceptable.
The transmission of the corrections of the base stations is very often done via mobiles, no need to have a pair of radios to connect directly.


Another point is the required antenna for reception of the standard L1 band, the L2 and perhaps the E5/L5 band.
These antennas are some more expensive than a standard GNSS mouse.


L1 plus L2 or L5 and the mentioned carrier sensing can bring values in the 50-80cm range. Without differential correction using just standard WAAS correction. A good antenna is paramount.
Multi frequency GNSS receiver are more stable in reception as well.


Anyhow: if we don't want to see autonomous docking, then all this is quite academic for our playground.
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Old 01-05-2020, 04:52   #80
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Location: Lelystad, The Netherlands
Boat: vd Stadt 44, Ben the Boat
Posts: 235
Re: GPS accuracy

But ...

You can start running base stations in the Mediterranean collecting RINEX so in post-processing you can see exactly where you hit ground.

"This module features a survey-in mode allowing the module to become a base station and produce RTCM 3.x correction data."
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