GPS errors

[Wild_Thing]

What About The Old Days When Their Was No GPS.Think Its Pritty Easy To Blame A Nav Aid.
Was The Skipper Of Sound Mind And Body At The Time.Sound Like It May Have Been At Night!
These Things Do Happen!
I Heard Theirs A New System Being Released Soon Thats Even More Accurate Than The Currant One.
They Will Also Have GPS In Mobile Phones So That the Parents Of A Child Will Be Sent An SMS If The Kid Goes OutSide A Certain Area.But Then Again I guess the phone Needs To Be Turned On.
Cheers Payney!

[Volvo]

Firstly one should never rely on a GPS/Plotter for safe navigigation, they are an aid or so the manual sez??.
Yeah where is Kerry when ya need im...
Tell ya way i do it if you can make sence of it good if not, i tried..
The manual for your GPS/Plotter should tell you how you can adjust or correct your unit if its out a tad so you will have to read it on how to do so..
In front of our local VMR base they have a brass plate with the lat n long for where that plate sits so its quite easy on a not so busy day at the boat ramp to drive the boat over this plate and checkout if both the lats n longs match up with each other and if need adjusting.
Also sez whether its on 66 or 84.
Prior to that i used to nudge my boat up against one of the red channel markers to the creek entering the boat ramp and do the same thing as ide previousely logged in its co-ordinates and just see if there was any error and what side of the marker my boat sat against with the plotter..
Far as Gladstone goes with the charts i have they is on aus 66 so my GPS/Plotter is set on Aus 66 and today have had no problemo's with either the GPS or the plotter with either landing over the same bommie, wreck or whatever and always check to see how close or far i am from the leads/ nav aids in the harbour when under way..
Comming back in or going out of a night time i NEVER rely on either unit but stick the noggin out of the canopy and go by the leads , also occasionally watch which way the wake from the motor is heading just to let me know if the wind n tide may be affecting my boat if those leads are adjascent to rocks!!!..
Okay see what you can make of all that and if ned be ask away..If i can elp i will..
Cheers

[Angla]

I got pulled up about 5 odd years ago at Flinders reef and they also said they had me on radar. I told them they would have seen me move as they approached because a tour/dive boat had just left and I thought they would take its place so I moved in while I could and showed them the plotter marks on the gps. They said I was still in the wrong place and the argument went on for a while. In the end I talked my way out of 3 breaches Because I think they did not have enough evidence.

I do tend to take these type on when I'm unknowingly in the wrong. I don't always win but sometimes.............Hey it's a bit of a blonde defense but if it works.

I also said I would read the big boards at the boat ramp where I launched as apparently all the information is on them.

And dont forget that all these depth limitations are at lowest tide so if the depth minimum is 2 metres and you are at 2.5 metres of depth at a tide height above 0.5 metres.......you are illegal.

Angla

[kc]

The skipper involved in this accident was very experienced, stone cold sober and watching his top line GPS like a hawk and had 2 guys on the bridge with him and was getting a 700 meter variation.

There is a us navy example of a GPS fixed on top of a bulding which, during a 6 hour period, at one 4 minute stage the building "moved" 1/2 mile at 14 knots??

As to testing this in court it is clearly something we are considering.

When booking someone in a green zone, fisheries first establish the position on a GPS and then confirm that position on the GBRMPA maps.....both of which clearly identify themselves as "aids to navigation" and "not for navigation purposes".

Interesting situation given everyone is innocent till PROVEN guilty.

KC

[Wild_Thing]

Another factor that can make GPS have a variation is the position of the aerial or even heavy cloud cover.
When you concider how they work by sending and recieving a signal to a satelite and timed to the millisecond , or something like that.
I admit they do vary a bit even if perfect situations!
Trying to prove the GPS to blame in court won't stand up because of all the warnings on GPS at start up , then you need to press the OK button to confirm you understand the warning.
This is also worth a mention if you have been fined for apparently being where you shouldn't.
Best of luck to your mate anyway KC . But if no one was hurt boats can be repaired & i think we can all learn from the experence.
Cheers Payney

[grex]

An interesting comparrison is to look at Google Earth & check the coordinates which appear in the bottom left hand corner of the screen against your GPS.

Not much good for checking spots out in the ocean but if you want to compare your GPS against another source this is an option.

Take a reading at home then check G.E.

On WGS84 the difference at my place was approx 20mt

Geoff