Here's one for you!

[biffothebare]

Here\'s one for you!

Hi all
On sunday I was stopped by a broads ranger on the river Yare.
He informed me that the speed limit on the river was 6mph ( which I knew) and that I was doing 7mph. I replied that my Garmin 178c was showing a speed of 5.9mph and that was why I did not slow when he came up behind my boat. He then got me to follow him until we were doing his version of 6mph, my unit read 5.3mph.
A quick search on the sat nav forums has revealed accuracies of 0.3%.
My reasoning is that sat nav calculates speeds "over ground" as it picks up on your absolute movement. Therefore tidal flow should not come into the equasion.( speed over water etc). Incidently I was heading into the tide. Surely the receiver is just that; a receiver? All calculations are
done by the satelites, not the unit? What does the team think?

 

[BrendanS]

Re: Here\'s one for you!

calculations are done within your gps, your gps has no way of contacting the satellites to give them anything to calculate.

 

[BlueSkyNick]

Re: Here\'s one for you!

Maybe your GPS is working in knots and the limit is miles per hour (which would seem odd). So his 6mph is about the same as your 5.3 knots.

sorry to correct you, the calculations are all done by the receiver not the satellites. The receiver receives signals from several, eg up to 12 satellites and then calculates its position on the planet based on the angles and timing of the signals it is receiving.

hope this helps

 

[jfm]

Re: Here\'s one for you!

You are correct that GPS gives you SOG not STW but many speed limits are STW. Maybe the ranger was accusing you of exceeding 6mph STW? Sounds like it, as you said you were heading into the tide. Did you clarify that with him? Was he accusing you of exceeding 6mph STW or SOG?

As others have said, calcs are done by your GPS not the satellites

 

[benjenbav]

Re: Here\'s one for you!

I was chatting to Chi Harbour Patrol recently and asked whether they used SOG or STW. "Whichever is lower" they said. Sounded a bit like trying to have your cake and eat it to me.

I think that it would be really dificult to prove a marginal STW speeding: "Must've been a bit of a back eddy there, officer" and as for a SOG claim "When was your GPS last calibrated, officer?"

Equally, I wouldn't really expect to be pulled unless I was (a) way over the limit and (b) creating lots of wash.

Then again, in my current fine craft, much over 8 knots and my ears start to bleed.

 

[biffothebare]

Re: Here\'s one for you!

Hi Big Nick
I've set the unit to read in mph. But I suppose it could be calculating in knots. Something to look into. Thanks to you all for pointing out the calcs on receiver bit. JFM; He didn't say one way or the other but I suppose thats what he meant. Now that I'm aware of the receiver doing the calcs I can see where he's coming from. Now I just have to find out how to get it calibrated.(Or go around at 5.3mph max!)

 

[Kawasaki]

Re: Here\'s one for you!

[ QUOTE ]
Hi all
He then got me to follow him until we were doing his version of 6mph, my unit read 5.3mph.
On what basis did He establish 'His version'?
We have a speed limit of 5 kts in and about My Marina.
The current however can reach up to 5 kts Springs no sweat.
So a Yacht going with the current under sail with a decent wind can be doing twice the 'Limit' easily.
However the Speed Cop does not intervene.
No prob with that.
A planing Mobo punching the Tide can be doing 4 kts and causing a big wake.
Bow facing skywards it looks like He's making 10 knts!
I think your Ranger was out of Order.
As long as You were not performing like a Tw$t (which I,m sure you weren,t) dashing about causing chaos and Mayem with wash etc and generally behaving badly.
Tell Mr Water Plod to f off!
His version of 6?
No. one eyeball I suspect.
As you say You were punching the tide.


Point that out nextime.

 

[SteveBates]

Re: Here\'s one for you!

This is the main reason we left the Broads two seasons ago for Lowestoft, You just have accept that if you are not a vole or a wooden trad' engineless sailing boat you are not welcome any more on the Broads. I have had several run ins the latest being charged a weeks visitor licence (£40)when a 24hour transition (£8.00)would suffice whilst moving inland from a seaport to a suitable lift out inland boatyard to make my escape. You have my sympathy. I have made several formal complaints with out any feed back what so ever.
They have radar guns now so how they determine speed over water/ground is open for discussion.

 

[MiskinDriver]

Re: Here\'s one for you!

Surely using a radar gun means you are measuring speed over the ground since the gun measures your speed relative to itself, and I assume the gun will be stationary. Therefore I assume that the speed limit must be speed over ground.

However, I was on the Broads last week on a hire boat, and the yard said that it was speed through the water - which is more logical since this is what will determine the wash, and thus possible damage to banks, voles etc.

So ....... I assume that you need to use speed through the water, unless you're cruising with the tide, or you are creating too much wash (which is a subjective measure anyway on the Broads) in which case you should slow down by the standard 'bit'. The rangers will still complain, though as long as that's all they do then I don't mind. Though I have to say the ones I saw last week were really pleasant.

 

[whisper]

Re: Here\'s one for you!

Please excuse my ignorance, but how on earth do they check/prove STW??

 

[jfm]

Re: Here\'s one for you!

"and I assume the gun will be stationary" - why, if it's on a boat?

Whisper, you are right. If folks just contest these fines and plead NG there will be no convictions becuase the "proof" is appallingly poor. NG pleaders will be acquitted, with costs.

 

[David2452]

Re: Here\'s one for you!

Most important law on the broads is never believe anything a hire company tells you.
Speed limits on the Broads are SOG and in MPH it is done that way as it is the only reliably measurable speed from the bank with radar. There is another bye law of excess wash so even if you're punching a couple of kts tide and doing 6 mph SOG (within the limit) they can still nick you for exess wake. However they don't, I find that the river parkies are, except the ones up the fetid dykes in the north, a sensible bunch and will not bother you unless you are behaving badly enough to attract attention. We have the Breydon launch in our marina (Devocean's old marina I think) and they are in the main, proper seafaring family peeps and I think that is were the difference lies. It really takes a lot before you actually get nicked, either persistent or massively over the top speeding like the guy who planed past us last year.