How far do you trust your GPS

[NevP 0]

I think the casualties from turning off the gps system would be more than a war! As far as I know all aircraft use the system also all commercial shipping. I think it may be political suicide to turn gps off.

It's even bigger than that bbay. The biggest group of users of GPS, by a huge proportion, aren't even interested in their position, they use it for very exact timing. Telecoms, electricity transmission, public transport and a whole bunch of other systems you wouldn't even think of, all rely on very precise timing to function. One of the side products of GPS working out a position is that it also needs to calculate it's time very precisely. It does that by comparing the signals from the satellites that all have atomic clocks. Every GPS receiver is almost the equivalent of having atomic clock accuracy in your pocket. (Although most consumer models will have a small lag in displaying it on the screen)

 

If GPS gets turned off it would cause unbelievable chaos. More than a little scary how much we're all relying on the US DOD.

[candyman 0]

I have navigated the CC twice now using GPS as the Primary tool, but always cross referencing with visual and other references, "takapau light should be red dead ahead", "we should be in 5m depth shallowing" "whale rock buoy off stb bow", yep we shoot the gap!

 

We have also used it to feel our way out of the Tamaki river in fog (very slowly) for the Simrad, but once again always taking what visual clues we could "red pole should be 10M ahead" , yes? (Thank heavans).

 

Its a very valuable tool as long as you dont use it as your only option.

 

Its a pity that it also tells you stuff you dont want to know like your VMG to the next mark is -0.1 kt (like in the parkup off waiheke on R1), or your next mark is 10 hrs away at current speed

[Murky 1]

Looks like we might have hit gottapay dirt in the Wide berth islands too....

...whereas I completely failed to round the Sugarloaf in a race in February, according to our Lowrance handheld.

 

From memory, it is out of whack with the bays up the eastern side of Whangaruru Harbour too, although the charting may be OK and it may just be the name labels on the bays.

Apparently the Poor Knights have been re-surveyed and the issue of a a new and more detailed paper chart is imminent (the original survey dating back to 1962-63). Don't know if it will pick up the Rimariki/Whangaruru issues - and presumably the GPS software will still be based on the previous (old) paper chart.

[John B 106]

I'll keep my eye out for it ... the poor knights is a cool place. Never stayed there though.

[Murky 1]

A number of the locals round here have spent the odd night anchored in Rikoriko Cave - a bit of a novelty although more suited to powerboats than yachts.