GPS - pay $120p.a. or be 100 metres out !

[jackdale]

Originally Posted by roland stockham

Worth remembering that some charts have more than 100m discrepancy compared to GPS! Always confirm nav with eyeballs, radar and depth sounder as well

That why you should check the Title Block to ensure that your GPS and charts employ the same horizontal datum, usually WGS84.

Of course in same place in the world, the charts are just bad.

[ArmyDaveNY]

Originally Posted by jackdale

That why you should check the Title Block to ensure that your GPS and charts employ the same horizontal datum, usually WGS84.

Of course in same place in the world, the charts are just bad.

Good advice. That's why I tell people that charts, whether paper or electronic, are just a guide. They will get you roughly where you want to go but you have to determine exactly where you really are and where you want to go. So too, the indicated navigational aids are just that, aids. You are the one who has to actually navigate. Too often we've seen buoys and other markers not where so indicated. They could have been moved by man or nature since the last update.

[sailorF54]

Originally Posted by barnakiel

Has anyone actually tested the forecasts for accuracy?

I mean what is the average accuracy of:

- one day forecast?
- two day forecast?
- three day forecast?

If we had such data, it would be very easy to tell how soon the forecast goes below 50% accuracy which is to say we might just as well toss a coin and derive our sailing plans from there.

barnakiel

No one has !
Weather scientists are certainly too dumb to have thought of that Nobel-prize-winning question

NCEP EMC Global Model Verification
Updated every day - Learning curve may be a bit stiff, though
I connect every week to follow the ECMWF vs GFS contest
And we Europeans are still in the lead, despite the huge amount of money the US have recently granted the NCEP (2 huge supercomputers to run 4D-var analysis!) to close the gap


One example: Top curve: Correlation between actual surface pressure over N hemisphere and predictions ranging from 24 to 240 h in advance for several models, averaged over a month.
US GFS : black
European ECMWF : red
Note that at 240 h the predictions are worse than what you could get by randomly picking out pressure values !!!
Predictions are deemed informative when the correlation coeff is 0.7 or more.
ECMWF leads over GFS by a bit less than a day on that criteria

[Dadrock33]

Originally Posted by barnakiel

Has anyone actually tested the forecasts for accuracy?

I mean what is the average accuracy of:

- one day forecast?
- two day forecast?
- three day forecast?

If we had such data, it would be very easy to tell how soon the forecast goes below 50% accuracy which is to say we might just as well toss a coin and derive our sailing plans from there.

barnakiel

. . . . if I was as wrong as often as they are, I wouldn't have a job. Being a weatherman is one of the safest positions available, you can be wrong daily and often in one day and they still won't fire you . . . . .

[buzzstar]

Originally Posted by TrentePieds

And worse still - to Google's "autonomous" car. I can't wait :-)!

TP

Yes it is. It buys itself.

[mooka2]

Originally Posted by ArmyDaveNY

What?!!! Next you're going to tell me that the Onion is not real news!!!

sorry.... pure caca de toro

[buzzstar]

[QUOTE=clivepil;2364552]Can anybody tell me is the following article for real or is it ''fake news''.....

Originally Posted by dennismckim

'Twas an April 1 joke.

The first two post to this thread were as quoted above although the first is shortened dramatically.

It shows how quickly thread drift occurs. The second reply should have been a a simple, "yes."

[ArmyDaveNY]

[QUOTE=buzzstar;2365619]

Originally Posted by clivepil

Can anybody tell me is the following article for real or is it ''fake news''.....



The second reply should have been a a simple, "yes."

True, true. Still, it wouldn't have been as much fun, unless you accidentally step in the caca de torro!

[sailorboy1]

some people take everything so serious they suck the fun out of things!

[fnoldsalt]

Originally Posted by clivepil

Can anybody tell me is the following article for real or is it ''fake news''.....

GPS - Soon Pay to Play For Increased Safety
US Announces Selective Availability For GPS Devices

April 1, 2017 by John Konrad


At a joint press conference today at Schriever Air Force Base, the United States Coast Guard announced a new feature to the GPS system they will start rolling out as early as January of 2018.
The “new” feature announced is referred to as “Selective Availability” and promises to improve GPS accuracy by “a factor of negative 200%” according to a press release issued by the USCG’s Office of Research and Development (RDT&E).
Those familiar with the history of GPS will remember that “selective availability” (SA) was a feature of early GPS systems which added intentional, time varying errors of up to 100 meters (328 ft) to the publicly available navigation signals. This was intended to deny an enemy the use of civilian GPS receivers for precision weapon guidance.
“The increase in terror activities around the globe have caused us to re-evaluate the GPS system. Said Captain Brian Winters, head of RDT&E. “We were mandated by the White House in April to develop a system to thwart the use of America’s GPS systems by terrorists and enemies of the state”.
Selective Availability was turned off by a mandate from President Clinton in May 2, 2000. Todays announcement did not explain why an old system of encryption – was reactivated rather than developing a new, more secure, system like eLoran but the answer likely lies in the large cuts to the USCG budget announced by the White House earlier this year.
A statement from the White House confirms the news. “The President thanks the USCG and Air Force for developing a system that will make America stronger with ZERO cost to the tax payer. This is Win-Win!”
Inside sources tell gCaptain that after SA is reactivated the USCG will be allowed to sell the Selective Availability decryption key to civilians at a moderate price of $9.99 per month. The USCG did not specify if that price was per device or if it will allow users to activate multiple devices on one account.
“We realize that 328 ft accuracy will invalidate many of the GPS features people rely on for use in their iPhones and Andriod devices which is why the White House is asking that we offer SA decryption keys for sale to the public.” said Winters. “The SA decryption keys will be sold by the same vendors that currently handle Transportation Workers Identification Cards (TWIC) card applications. This is a plug and play solution. People who want to purchase SA decription keys will simply have to visit their local TWIC center, be fingerprinted and apply for the special key that will decrypt the SA signal. Those fingerprints will allow any mobile phone with a built in scanner to decrypt the key and receive GPS signals within a 4 meter RMS (7.8 meter 95% Confidence Interval) horizontal accuracy.”


In a series of tweets today President Trump wrote:

“We built GPS for 3.6 trillion $$ and we are giving it away for free. Crazy!!”

“”We are going to have an unbelievable, perhaps record-setting turnout for these encryption keys. People from around the world will love them. It is an exciting time for our country!”


“This SA Plan is brilliant! It will pay for the entire Mexico Wall AND will allow us to start work on my next BIG project… a Canada Wall!”


Eddy Cue, Apple’s senior vice president of Internet Software and Services, responded to the presidents tweet with this remark “Thats ok, our phones work just fine with the European Union’s Galileo positioning system.”


US Announces Selective Availability For GPS Devices – gCaptain
__________________

I did a check on Snopes.com and they do not mention it as a scam?

[TrentePieds]

But why would it matter? Surely we have far more important things to worry about?

If you don't know at all times within 10 boat lengths (or less for some) where you are, you need to go sit in a corner for a while and think about your basic navigational skills :-)

If you are 2 cable lengths off a shore, it's your eyeballs and a sounding lead you need, not a GPS! If you are in mid-ocean and doing 7 knots - or even 17 - 10 boat lengths is a triviality. Make yourself a cross staff from stuff lying about your navigating station anyway, and remember that ANY modern wristwatch keeps time as well as Harrison's vaunted time-piece. Surely you have at least ONE time piece aboard that is either on Greenwich time, or on the time of your home port, which - these days - amounts to the same thing? Can't believe you wouldn't have a lodestone aboard if you look hard enuff. Cap'n Bligh did it, so why can't you?

Good Lord! Don't let the Empire of Fear get to you! Aux armes, citoyens :-0)!!

TP

[buzzstar]

Originally Posted by fnoldsalt

I did a check on Snopes.com and they do not mention it as a scam?

They are humorless too, despite being well funded. Or maybe they did not notice, were not asked, or were clueless. Remember to them GPS means Gross Political Slant.

[buzzstar]

Originally Posted by TrentePieds

But why would it matter? Surely we have far more important things to worry about?

If you don't know at all times within 10 boat lengths (or less for some) where you are, you need to go sit in a corner for a while and think about your basic navigational skills :-)

If you are 2 cable lengths off a shore, it's your eyeballs and a sounding lead you need, not a GPS! If you are in mid-ocean and doing 7 knots - or even 17 - 10 boat lengths is a triviality. Make yourself a cross staff from stuff lying about your navigating station anyway, and remember that ANY modern wristwatch keeps time as well as Harrison's vaunted time-piece. Surely you have at least ONE time piece aboard that is either on Greenwich time, or on the time of your home port, which - these days - amounts to the same thing? Can't believe you wouldn't have a lodestone aboard if you look hard enuff. Cap'n Bligh did it, so why can't you?

Good Lord! Don't let the Empire of Fear get to you! Aux armes, citoyens :-0)!!

TP

Hmm, I always know where I am; it is the location other people, places , and things that are of concern.

[TrentePieds]

Wasn't "aimed" at you Buzz :-) Our friend the OP sounded all worried, so I thot an encouraging word about the triviality of GPS might be in order.

As for April Fool's jokes, yeah, we'd best all remember that what one culture finds portentous another culture might find laughable - or even incomprehensible - and vise versa :-)

TP

[buzzstar]

Originally Posted by TrentePieds

Wasn't "aimed" at you Buzz :-) Our friend the OP sounded all worried, so I thot an encouraging word about the triviality of GPS might be in order.

As for April Fool's jokes, yeah, we'd best all remember that what one culture finds portentous another culture might find laughable - or even incomprehensible - and vise versa :-)

TP

Not aimed at me? You shot an arrow which landed you not know where. In no way was I even slightly offended, and previously had not even thought about the possibility. Although I've said it before as a quote, it is worth repeating here as a paraphrase of what Churchill has observed: The posters to this forum are separated by a common language.