Might be time to buy a sextant

srm said:
That is what I thought at first; that there was a chart datum error. However a couple of years later taking a deeper draft vessel in the same channel the GPS plotter had me mid channel so its reasonable to assume the first time was a GPS error.
Click to expand...

Same plotter ? Same Chart system ? Same updates ?

I have as example CM93v2 ... CM93v3 ... Lowrance Mapcreate N and S Europe .... Mapmedia .... KChart v2 ... Navionics ... scanned Raster .. BSB-KAP .... UKHO digital ... etc as well as paper folios and the offsets found when comparing is striking. What is really surprising is that they all derive base hydrography from same sources. You would think they would agree.

But I agree that a serious error as you described earlier is worrying to say the least.

Last example I had was in Swedish Islands ... I had created a route through a series of islands / rocks. I have conversion utilities that allow me to take waypoints from one system to another. The exact same WP's of the route had me clipping islands, through a few rocks ...
It only goes to support the old advice : Mk1 eyeball ......
 
Buck Turgidson said:
There is an awful lot of spurious information about GPS in this thread.
Might I suggest anyone who is interested look at the actual data rather than listen to this guff!
Real Gen
More real Gen
Truth about SA
Click to expand...

You can read and believe those links if you wish ... generally of course not to be argued with ... BUT having been in two War Zones assisting Fuel Distribution - I can tell you straight - degradation or denial of service is and was a reality .....

The new generation satellites have been delayed in launch ... previous generation satellites running well over time are having 'outages' ....

Do you know how SA works ? It was based on the Ground Tracking Stations checking / updating the sats ... random errors were uploaded to influence the positional data a civilian plotter would calculate. You honestly think that is not possible now ?

Consider the heated debate and final agreement between USA and Europe regarding Satellite Navigation and denial of service. It is no fantasy - it is a reality. The agreement stands today - Europe agreed to degrade and or switch off Galileo in co-ordination with US GPS if requested. Augmentation will be first to go ... then its a downward path ...

It may not be called SA today .... but it has even greater potential today than ever before.
 
Refueler said:
You can read and believe those links if you wish ... generally of course not to be argued with ... BUT having been in two War Zones assisting Fuel Distribution - I can tell you straight - degradation or denial of service is and was a reality .....

The new generation satellites have been delayed in launch ... previous generation satellites running well over time are having 'outages' ....

Do you know how SA works ? It was based on the Ground Tracking Stations checking / updating the sats ... random errors were uploaded to influence the positional data a civilian plotter would calculate. You honestly think that is not possible now ?

Consider the heated debate and final agreement between USA and Europe regarding Satellite Navigation and denial of service. It is no fantasy - it is a reality. The agreement stands today - Europe agreed to degrade and or switch off Galileo in co-ordination with US GPS if requested. Augmentation will be first to go ... then its a downward path ...

It may not be called SA today .... but it has even greater potential today than ever before.
Click to expand...
Mate. 35 years in aviation. First 12 were military aviation. Served in all of the 1990s conflicts and in civil aviation since the turn of the century including teaching GPS theory as one of many subjects ,so you don't need to lecture me on GPS.

And if it's fuel distribution in a war zone you want to discuss I can do that too:
 
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??
Poor threads on here get killed early right left & centre these days. ?
 
AntarcticPilot said:
I'm in Hong Kong right now, and the accuracy of GPS when in the urban canyons of Hong Kong is pretty bad - hundreds of metres from where I actually am! Anywhere where than can be multiple paths caused by reflection or refraction from buildings, cliffs or whatever can degrade the accuracy quite severely.
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that kind of reminds me of being lost in London city centre with a sat nav that kept loosing its signal because of the high buildings .
 
DownWest said:
Decent quartz watch does it. Just correct it off the BBC time signal on long wave. There is always Slocum's 'Tin Clock' (and Lunar system)
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It's becoming more and more difficult to find radios with LW these days, to replace old ones as they become unserviceable.
Car radios no longer have it either.
I get my Radio 4 on the BBC Sounds app on my phone currently, ( since I got my Bluetooth hearing aids?), and the time signal is always about twenty seconds late.
 
Buck Turgidson said:
It's why mobile phones use wifi assistance. The use wifi signal strength for distance triangulation.
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You talk about 'gaff' ????

Suggest you read up about AGPS on a Mobile Phone .... its actually the GSM signal - nothing to do with WiFi ....

Oh yes - Fuel Distr .... if it wasn't for people like me working with Strategic Fuel who were based in Bahrain during GW1 - the Coalition Forces would have been seriously short of fuel.

Oh and the picture you showed of Air to Air .... developed from pioneering work by Flight Refueling in UK - who my Father was a member of the team ...

????????
 
Daydream believer said:
If you think that is hard, then you want to try pouring diesel from a 20 litre can into my deck filler in a F5 without getting it all over the deck.
By the time it has all gone down your oilies & into your boots you will wish you had not bothered. :rolleyes:
Click to expand...

Delivering one of the worst boats I have ever been on ..... Match 35 .... from Travemunde to Ventspils. We asked seller - Yacht Charter Co based in Travemunde - to supply 40lts + full on-board tank for our Baltic trip. Tank was full ... but they supplied the spare fuel as you had ... 20lt plastic drums. We had asked for small handy containers ....
The stink of spilt diesel that trip stays in memory along with the cramped sea berths, the absolutely full blocked holding tank that no one could get to, the mainsail reefing that didn't work, the creaking mast heel in the keel area ..... UGH !!

Oh and yes - about 3 months later while racing of Kolka - she lost her keel ... something I had warned new owner to look into to prevent ....
 
Refueler said:
You talk about 'gaff' ????

Suggest you read up about AGPS on a Mobile Phone .... its actually the GSM signal - nothing to do with WiFi ....

Oh yes - Fuel Distr .... if it wasn't for people like me working with Strategic Fuel who were based in Bahrain during GW1 - the Coalition Forces would have been seriously short of fuel.

Oh and the picture you showed of Air to Air .... developed from pioneering work by Flight Refueling in UK - who my Father was a member of the team ...

????????
Click to expand...
It was 20 years ago. These days it's a hybrid system.
 
Buck Turgidson said:
It's why mobile phones use wifi assistance. The use wifi signal strength for distance triangulation.
Click to expand...
Even that doesn't help much in an area where a small building is more than 10 stories high - the multipaths and reflections basically reck the geometry. It isn't so much the strength of the GPS signal - there's usually plenty, it's the complex environment. And Hong Kong is a place where you get WiFi and cellphone signals even on the underground!
 
Buck Turgidson said:
It was 20 years ago. These days it's a hybrid system.
Click to expand...

Please think about it ...

You are confusing the use of WiFi to augment location when you are LOGGED into a WiFi area .... with that of out in the street - which "Antarctic Pilot" is talking about ... where GPS is augmented by Mobile Phone Network triangulation.

20 yrs ago ????? Its still same today ... aGPS is GPS location augmented by Mobile Phone triangulation.
 
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