David of Essex
Well-Known Member
I have an ST60 fitted and the log showed a distance of 20.60 miles and the actual distance was 32 miles. Any suggestions.
David
David
Log Error
- Thread starter David of Essex
- Start date
Powersalt
Well-Known Member
Log under reading speed and as such distance. Possible cause, fouling on paddle wheel or never calibrated properly. Other option is tide taking you along to make up difference ( tide will not be shown on log).
You can calibrate on measured miles along the coast.
You can calibrate on measured miles along the coast.
sailorman
Well-Known Member
Tidal flow ????
David of Essex
Well-Known Member
Paddle wheel free and clean. Small movement and the speed shows fine. Interested to learn how it should be calibrated.
David
David
Powersalt
Well-Known Member
Sure there are more learned folk on here than me, but for what its worth heres what I do with new installations etc. Where you keep the boat, on sea or along river there has to be identifying land marks. So between to points you know the distance. Run up one way and then back timing the travel and noting the speed. ( return way counters the tidal flow) So from the known distance traveled you have a known time. Quick calculation will give you speed travelled. Check that against you speed noted on the log and you know the error. You can also do it by the distance recorded to actual. Now on some charts in certain places they show a measured mile ( this might be showing my age here a bit) but there is places which have recorded points.
Another way and maybe easier just to check is to calibrate it against the gps which will give you course speed made good. Depending how accurate you want to be, but I think looking atnthe chart and checking springs or neeps etc you would have a pretty good idea if the tide was with you or aginst and at what rate of knots etc. Adjust to that is circa ok. Hope that helps
David of Essex
Well-Known Member
How do I adjust the ST60 to accommodate the error?.
hlb
RIP
A log is never going to give you perfect distance, it does not understand tides, only GPS and a chart plotter can do that. But even then AFAIK none will take account of tide. How ever, once set off, your speed will be taken into concideration and ETA will be provided, however this will change as the tide changes.
So, the distance through the water and distance over ground can be much different.
D
Deleted User YDKXO
Guest
Read the manual. The calibration procedure will be in there. It's always worthwile accurately calibrating the log as one day, sooner or later, the plotter screen will go blank and you'll be left with the problem of getting home using traditional nav methods
David of Essex
Well-Known Member
Haydn I can see how the speed through the water and speed over ground can be different but I can't see how the distance is different. If your measuring from a chart that is the distance.
David
Deleted User
Can't find adjustments for log in manual.
David
Deleted User
Can't find adjustments for log in manual.
David of Essex
Well-Known Member
Have just been in touch with Raymarine HQ. I have been supplied with the ST60 + Graphic Display hand book with product, which is the wrong one. Muppets come to mind.
David
David
jimg
Well-Known Member
Well, imagine you were drifting with no power. You will still travel a actual distance on a chart, but the log would be zero.
D
Deleted User YDKXO
Guest
If it says 20 knots on the log and you are proceeding against a 4 knot tide, your speed over the ground is 16 knots and your speed through the water is 20 knots. Similarly, if you were going in the opposite direction, your speed over the ground would be 24 knots and your speed through the water would still be 20 knots
Mmm, I've had many boats with Raymarine (previously Autohelm) log/sounder systems and the log calibration procedure has always been in the manual (not the Quick Start but the main manual). In fact you can download the ST60 manual from the Raymarine website here http://www.raymarine.co.uk/products...ies/speed/a22009-p/?esctl370149_assetdet=6662 and I see that the calibration sequence is explained in section 4.3. I wouldn't muck about with the timed speed runs. Find yourself a flat piece of water at slack water, run in a straight line and adjust the calibration factor up or down until the indicated log speed matches the GPS speed from the plotter
maxi77
Well-Known Member
The pesky water moves and you move with the water, so the distance you travel over the ground is like your speed different to the distance you travel through the water.
