How often do you clear and remap your Zero Off?

[Horton]

How often do you clear and remap your Zero Off?

[aupatking]

Huh? Didn’t know that was a thing

[ozski]

Almost weekly. Slalom its not so bad but the mapping on the jump course seems to out of whack quite a lot which means switch is not engaged through the ramp which is a big deal. Seems to be the same on all three of the boats we use including the new Nautique.

[LeonL]

I voted never, but that's not really accurate. It's just almost never. I think I've done 2-3 times in 10 years. There are people that say it might need it done more than once some days. As @ozski said, jump is pretty critical.

[aupatking]

Outside of jump, which has been explained here, what is the function of clearing and remapping. My beeps seem to line up and my times are almost always dead on. I got a disagree earlier for not knowing.

[MattP]

You will always get good times with a poorly map courses the boat does not know where the buoys are it is just assuming where they are based on the entrance gates position GPS coordinates that you programmed when you floated by. You want the boat to react properly between these imaginary points when it is throttling to make up the time. I’ve been in been in some boats that need to be remapped weekly more than likely it’s due to the satellite drift and location of the lake or failing pucks. @Jody_Seal once told me to remap every time you skied. Do I do that? No, but I try to do it every few weeks.

[Kelvin]

Yea, I just noticed GPS had drifted about 30ft or more in the slalom course on one of my boats. Will be remapping it the next time it gets used.

[RichardDoane]

pay attention to the relationship of the boat guide/pylon and the beep when engaged. as soon as it starts to be different, i's time to re-map

[ski6jones]

Yeah. Gotta watch those gate bouys. They move all over the place. Sometimes mine are on the shore.

[T_C]

I just got back from skiing with @twhisper at Liquid zone and ran lots of nice passes. Skied for the first time back yesterday and could not run a pass. I could not get the right position on the gates to save my life. When I got in to drive the boat I noticed the boat was 20' past the entry gates when zero off beeped! When I blamed the crappy set on zero off and all my ski buddies asked me what i was smoking? I re mapped the boat!!!!

[BrennanKMN]

I do a mental check a few times a year by comparing the beep and the entrance gate. If that is accurate I don't do anything. I have yet to have it drift, even after sinking the course for the winter.

[Kelvin]

IWWF rules require remap if the beeps have drifted more than 2.5m from the buoys.

[Horton]

I do not understand how GPS can be wrong since it is just data but I think it should be standard procedure to remap every 90 days or so. I have heard more than one story in the last month about skiers having issues skiing behind a boat until they reset the ZO and then everyone goes back to skiing good.

[aupatking]

Thanks for the thread @Horton. I seriously had no idea

[Ed_Johnson]

Thanks for the thread. I set mine 5 years a go when I got a new CC200, and as long as the beeps were close I took it for granted. Rechecked it today and the beeps were about 3'-5' off, when you focus closely. Remapped it and it is now perfect. No wonder I couldn't run my 43 off pass !!!

THANKS BOS !!!

[DW]

+3 on thanks for posting. Friends boat was off and giving some random slow times (felt slow also), this thread prompted me to listen to where the beeps were happening and sure enough, ~10' off. Remapped seems better but the beeps are not quite on top of each other for opposite direction pass. Would be interesting to get an explanation as why or how the signal can shift over time.

[Andre]

Pffffffff!

When Zero Off drift, i just buy a new boat...

[Ed_Johnson]

@DW ... Try remapping from the other direction. When I first remapped mine East to West, coming back West to East was off. I then remapped again, from the other end, West to East, and for some reason both directions were now spot on. Not sure why that mattered, but it's now perfect both directions.

 

 

[DW]

@Ed_Johnson : I suggested that to the boat owner and also was thinking of doing that and naming it a different course to see the effect (okay shoot the damn engineer).

Are you saying simply to remap the same course but opposite direction, just so I am clear?

[Kelvin]

@DW you don’t want 2 maps of the same course. Can do screwy things.

[aussiemc]

In my experience, remapping is a great idea, but I think one of the most important things to do is occasionally delete all courses from ZO and re enter as a new course. I always do it before a tournament to ensure accuracy. It's especially important on multi lake / course sites.

[ski6jones]

I know in order to get a very accurate location with handhdld GPS requires the system to stay in one location and average for a while. Wonder if this is related why the points drift.

[Ed_Johnson]

@DW ...you said..( Are you saying simply to remap the same course but opposite direction, just so I am clear? )

 

YES !!!!! It worked perfectly for me.

 

 

 

[DW]

@Ed_Johnson : Thanks, that is what I interpreted your comment to be.

@Kelvin : What are those screwy things?

 

Awesome, contradictory comments, makes this thread perfect learning tool and why this site is great. Kudos to the Great Galactic Leader...(I am glad that @Dirt & @MS don't have panda power).

 

And - looks like the poll needs an addendum: after reading this thread, now how often are you going to remap, and will you do a bidirectional process.

[eleeski]

GPS accuracy is a few meters. " the government commits to broadcasting the GPS signal in space with a global average user range error (URE) of ≤7.8 m (25.6 ft.), with 95% probability. Actual performance exceeds the specification. On May 11, 2016, the global average URE was ≤0.715 m (2.3 ft.), 95% of the time." NOAA.

 

There are ways to improve the accuracy but typically use more time or fancy expensive setups. Is the single puck ZO less accurate?

 

GPS is accurate to measure speed through the course to .01 second regardless of any drift. "The government provides the GPS signal in space with a global average user range rate error (URRE) of ≤0.006 m/sec over any 3-second interval, with 95% probability." NOAA. That's .01 mph with an AWSA tolerance of .5 mph!

 

I believe the satellites are recalibrated regularly to keep long term drift from moving your map too far from the course over longer periods of time. I don't know the rate of drift or re centering. But the airport is still in the same place on my 15 year old aircraft GPS.

 

So when you map, it's random if you are at the middle of the GPS error or at the edges. If the beeps end up a long ways from the real course, remap. If they are pretty close, stick with your mapping. .7m or 2.3ft is pretty close.

 

Remap before a tournament. At least you'll have that day's error right. Unless they correct the satellites mid day. Then, you'll notice beeps in the wrong places (and remap).

 

The quality of the mapping, the condition of your ZO, the satellite view from your site and other local factors can all degrade the signal accuracy. You might nee more frequent monitoring.

 

All bets are off in Australia as the continental drift there is more than the (most accurate) GPS errors.

 

Eric

[skiep]

Every Day !!

[Kelvin]

@DW, a friend on a single lake had his course mapped twice in the system. As a result, the boat would pick a different course on each end of the lake and the wait timer didn't work. He has the older round dial in his boat and wasn't familiar with the auto course selection settings. Clearing out one of the courses fixed the issue.

[A_B]

Our course is anchored at the east end and is hooked up to a boat winch on the west end. When we have high water in Spring I map a “High Water” course that floats further east and then go back to our normal course as it comes down. I remap regular course maybe once a year or skip a year.