Zero Off used for Wakeboarding w/ current

[wviveen]

RE: What R U Guys Talking About?

Is there already more info on the software update ?

[Fast351]

RE: What R U Guys Talking About?

The reason GPS works well for speed control has nothing to do with how accurate it can locate a position. I'll try to explain (and yes my job involves using commercial GPS).

Explanation 1: There are two measures of GPS that determine it's capabilities. One is accuracy, the other is precision. Think of it this way: I am standing at location X. My GPS tells me that I am at location X + 5 yards. The accuracy is 5 yards. However, it actually tells me I'm at location X + 15 feet. The precision is 1 foot. Now, if I move 3 feet in one second, my GPS tells me my location is X + 6 yards, but my speed is actually 3 feet per second. As you can see, the accuracy of the absolute location is irrelevant to determining my speed. It's the precision (or resolution) that matters. You have to be able to tell you moved a foot, but you don't really care if you're absolutely within one foot of where you say you are.

Example 2: If you look at the output of a GPS unit (the NMEA stream) and look at the longitude and latitude, it comes out in decimal form that looks something like -93.12345 and you can see the last two digits slowly drift up and down. It's like a minute or two cycle. Obviously that prevents you from locating with any more accuracy -93.123, but if the last two digits move as soon as you move, and in the correct direction, you can easily tell how fast you're moving with much greater precision than absolute location gives you.

In other words, you don't have to know exactly where you are to know exactly how fast you're going.

If you're interested, the GPS sensor ZeroOff is using is the Garmin GPS18-5Hz version, which updates speed every 2/10th of a second. That's how they get the quick response:



https://buy.garmin.com/shop/shop.do?...1&tab=gps185hz

[pjdave]

RE: What R U Guys Talking About?

Thanks Fast351, but I dont really care how it works, because it doesnt. The "fly by wire" versions of pp were bad but this product is useless in tidal applications. Currently we have to set the speed off the nautique speedo and adjust up or down depending on which way the current is headed (which also changes on the inside or outside of a river bend). annoying. Relying on Gps alone is not the answer. Sorry about the rant, Im just over people saying how good it is, next time they should test it in more than a sunny open lake.

[Fast351]

RE: What R U Guys Talking About?

Yeah, I'm with you. I wakeboard and surf in the river myself, and the Perfect Pass is great. GPS would be useless for me. I'm sure it's a great speed control for slalom, but for wakeboarding and surfing, speed over water is what matters, and if the water is moving, the GPS is useless.

Glad to have a PP :mrgreen:

[wviveen]

RE: What R U Guys Talking About?

I use zero off frequently on a lake (no current) and on a river with current. On the lake it works perfectly and is reall nice while driving the boat. But on the river with current it is really annoying changing the speed every time you turn around. Should be pretty easy to link the output of the digital speedometer which is already in the boat to the zer off, I think ?

[skiinxs]

RE: What R U Guys Talking About?

As I was getting familiar with the screens on my ZeroOff last night I noticed a "current" menu choice. I recently upgraded to version P, and didn't see it in the previous version. Since I don't ski in body of water with a current (and would only be concerned if I was tricking, since slalom course and jump are speed over the bottom), I didn't spend any time trying to figure it out, but the "P" upgrade may be of some use to soem of you.
Dave

[mattoz]

Over the past week I have been corresponding with ZO regarding the new software revisions. I have just uploaded a 08 210t(ZR6) ZO unit with the latest version – P. The unit version it replaced was J. ZO explained that development of the software throughout the year has been ongoing, thus the reason for the large number of revisions. This weekend PJDave, JBwake and myself will trial the latest version on our local river (tidal, bendy and variable width).

Version P has a “river mode” function. The ZO supplied info below best describes this new function.

Based on this information, my early opinion is that the new river mode function does not adequately addressed our river current speed compensation issues. The version P software just formalises a human machine interface process that we the users already do. On the bright side, it appears that ZO’s customer service is on the up, I have been very pleased with their willingness to listen to my rants.

======================================
On the wakeboard screen with river mode on with Version P ZO code:

“You'll then see two new parameters on the center of the screen above the speed setpoint, first a text icon saying UPStream/DNStream followed by a speed number. There will be a new highlight block that you can move around the screen between the two river mode parameters by tapping the SELECT button. Highlight the new speed value and use the arrow keys to enter your estimate of how fast the current is (Let the boat drift and see how fast it moves). Then use SELECT to highlight the UP/DNStream icon. Tapping the DOWN arrow will place the system in DNStream mode, UP arrow for UPStream mode. If the highlight block is off, then the arrow keys will go back to allowing you to modify your baseline setspeed as always.”

“The idea is that you set up your desired speed over the water using the normal speed setpoint, enter an estimate of river current using the new River mode number, and use the River mode UP/DNStream icon to switch back and forth during the turns as you turn against or with the current. The river current estimate value will be added to (DNStream) or subtracted from (UPStream) the base speed setpoint and should deliver a reasonably consistent speed over the water. If you disable the River Mode, the new icons will disappear and the setspeed will track the normal setspeed regardless of direction.”

“There is no paddle wheel involvement”

[Laptom]

ZO uses GPS if I'm correct. So then they can see if I turn the boat for going up or downstream. Only an initial setup is needed imho to let the ZO know if it's driving up-or downstream. Perhaps something for revision Q ;-) ? Then you will not have to push the up and down buttons when turning.
Nevertheless, good progress and customer care ZO! I thnk it works for us, our river is pretty wide (constant) and straight, so the current doesn't vary that much (except at bridges). Still the current will vary in function of time (flood or eb have different effects on the current), so probably you'll have to calibrate the tide speed every hour or so.