Tridata ST 60 - Help

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spring

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Tridata ST 60 How do you calibrate (check it’s working OK for speed, using a half-mile measured channel markers? I have read the handbook, and still can’t understand how it will work “ press key at start of calibration run “ but how will the unit know how fast the boat is travelling.
Can some one explain?
 
To do a measured run, do it twice on the same piece of water, following the same track/distance each time. Half a mile should do it.
Find a good start point that has two recognisable features to align the start and note the position. Do the same for the finish point.

Try to do this in calm conditions, at slack tide.
Use GPS Speed Over Ground function.
Start from behind the start line and throttle up to 7-8kts if possible.
Approach the start point at a steady speed on the SOG
As you hit the start(noting the transits) push the calibration key.
At the end of the run, press stop and note that the SOG remained constant,
Repeat the run in the other direction.
Now your unit should read as the average speed between your runs from the SOG observation, which moreorless cancelled out any tide/wind effect because of doing it in both directions.
Adjust the unit if needed.
 
It does not matter how fast the boat is going within reasonable limits. You are really calibrating the log and this in turn will automatically calibrate the speed.
Do 2 runs in opposite directions. One run immediately following the other run to cancel out the effect of tide.
Compare your logged distance with the known distance and correct unit as necessary.
 
Groundspeed has no connection with log readings, logs read speed through water for calculating items like tidal vectors, (you know - real navigation). Make several runs in opposite directions, the more runs the more accurate will be the final result.
 
I have no idea what you are on about. SPRING, Simply make the log speed the same as the gps speed--with no tide running--then you will have calibrated it.
 
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Can some one explain?

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I'll have a go. The ST60 measures distance, not speed. The little paddlewheel turns so many times per metre travelled through the water. The instrument converts the distance to a speed reading by seeing how far you travel over a short time interval of a few seconds

So that's why you calibrate it over a set diatance. I see you are Chichester based. There's a half mile marked in the Emsworth Channel on the Hayling side. Two sets of yellow posts with X topmarks. Start the calibration when the first pair are in line and finish when the second pair come into transit, from memory you have to do it 3 times for the ST60

Half a nautical mile is exactly 926 metres - have a look at the chart and you'l spot the marks
 
a fine attempt, but dearest spring has already read the book, and has decided to take the "huh, i can't see how thatt would work" approach instead of just pressing the button.

an alternative is to get a man on board who can do these in three seconds, and diagnose loads of other stuff at the same time, such as that nice chap at Marine Electronic Installation 02392 326366
 
I know the book seems confusing when you read it but when you follow the instructions and give it a go it becomes clearer.

If you first use the method written in the manual, by going up and down between any two marks, you can then check it using the GPS too.
 
Thanks all. Thanks tome when I mentioned “half-mile channel markers” it was those Emsworth measured markers I had in mind. I have all ways found it annoying that my hand held GPS would show us sailing up to 2.5kts faster than indicated by the ST60 (taking tide influences into account)

You can just press the button, but to under stand the how and why is best
 
If it's that far out then you may find you have a problem with the paddlewheel - it could be it's not rotating freely and needs a good clean. Try this before making any adjustments, and make sure it's properly aligned fore-aft
 
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