Measured miles?

[ITH]

Got a chum in Ramsgate, who wants to check his log against a measured mile run. Can anybody suggest a source that could provide information on the location of measured miles in the area?

 

[Skysail]

AFAIK the only source is a local chart. But they are not very common.

Maybe he could construct one by using suitable local transits? It does not have to be precisely a mile
.

 

[earlybird]

I wouldn't get too hung up on calibrating over a measured distance. There's a good one where I sail which I've used for interest, but, IMHO, a quick check against a GPS is as good and much easier.
My log is a Raymarine, I like to think it's accurate but it's affected by the circumstances. At low speeds it under-reads, at higher speed it over-reads, it varies depending which tack the boat is on, and there also seems to be some difference between motoring or sailing.
Don't ask me why! I just set it to match the GPS at a typical speed of 5 or 6 kn. Making allowance for any current of course.

 

[Bosun Higgs]

Got a chum in Ramsgate, who wants to check his log against a measured mile run. Can anybody suggest a source that could provide information on the location of measured miles in the area?

Any canals nearby? If there are, thats the answer but bear in mind the mileposts are statute miles

 

[johnalison]

It's not always as easy as choosing a canal. Some canals have a current running, especially in the Netherlands. I have also found that the speed shown is affected by the depth, though this seems to vary between boats. In my case, in less than about 5m the GPS speed is reduced (ie, the boat is slowed) but the water-log shows a higher speed, presumably because the water is "squeezed" under the hull.

Also, my log, whose transducer is near the bow, shows a higher reading under power than sail. The only explanation I can think of is that a stream of water is generated by the prop whose effect is felt ahead of the prop.

Calibrating a log in one go is difficult, and I tend to adjust mine in small amounts over several sessions before arriving at a compromise reading which suits me and is about 0.1 kn fast in the middle of the range.

 

[Ubergeekian]

Got a chum in Ramsgate, who wants to check his log against a measured mile run. Can anybody suggest a source that could provide information on the location of measured miles in the area?

Isn't it easier to do that calibration with GPS nowadays? Or borrow a proper (trailing) log and check it against that...

 

[fmoran]

Arran - about 500km north!

 

[SAMYL]

Island Magee, Belfast Lough - bit out of your way though

 

[Bandit]

There is one on the Isle of Wight in the Solent, but a long way to go for that.

Most people check the tidal flow book and run up or down a current four or six times and note down gps and log readings and average each and adjust the log accordingly.

 

[Aja]

We've got plenty up here... as previously mentioned Isle of Arran and also Weymss Bay - Skelmorie.

Borrow a hand-held GPS and it will be just as much fun.

Regards
Donald

 

[Twister_Ken]

One in Southampton Water, but bizarrely the UKHO smallcraft chart shows it as two runs of 968 metres.

Easier to do it against GPS SOG at slack water, or if no slack water, one uptide, one downtide run on reciprocal course, and average the SOG out.

 

[DJE]

I seem to remember that there's one between Anvil Point and St Albans Head but you may need to make some adjustment for the tide there!

 

[ITH]

Measured miles

Thanks for the suggestions: and invitations to far-away measured miles. I guess I'll be lending him a hand-held GPS to get him started.

Cheers.