Zero Off GPS Speed Control

What are thoughts on this? Possibly somebody to challenge Perfect Pass?


http://www.zerogps.com/index.php

I like it, but i ride where there is a pretty decent current. wouldnt that mess up the speed. I.e. for wakeboarding you want the effective speed, with current taken into account, not the gps speed.

I dont think it would mess it up that much. It seems like a very good idea to me. It looks like it would be a great alternative to PP because you would not have to install the paddle wheel in older boats. They say nothing about wakeboarders in the website but I dont see why it would not be as good or better than PP.

I looked into designing and building my own GPS based speed control system about a year ago. At that time, I found that the rate at which the GPS receiver modules updated the velocity value was not fast enough for this type of closed-loop control. I'm not sure why this is but it's probably a limitation of the GPS constellation itself.

Also, I'd be curious to see how well it measures speed in a tight turn.

Paul, It has nothing to do with the GPS constellations. If you have the money, you can get a GPS receiver that updates as fast as you want. Some of the ones I sell will update 20 times a second, with sub-centimeter accuracy when combined with a second receiver acting as a differential base. Cost equals $30,000+. How many you need? To quote Alan, "It won't take long...it just takes money."

"It Will never work" they have a Ski'r on the front page of their website. Dont they know Skiing is "not cool" and has nothing to do with Wakeboarding. LOL LOL

If you dont know Im just kidding, The Idea is awesome.

Im all for it. PP seems like a great unit but with out serious compition how can you expect to see PP evolve. Weather this unit works or not I think its great to see another speed control system on the market.

Grant, I was not saying that skiers aren't cool. I just know that PP has a wakeboard model and a skier model. They seem to be catering to the ski community with the course options.

I think, that the wakeboard mode on PP is by speed and the skier mode is by engine RPM. If I am right then Zero Off would actually be closer to wakeboard mode PP than Skier.

I really like this idea because I would not have to drill a hole in the bottom of my boat to install it.

Jon: I wasent pointing you out I hadnt read you post. But after I saw this and read your post I see you might have thought I was talking about you sorry. I was just poking fun at the stereo typical wakeboarder ya know "that guy"

Kevin - I realize speed is calculated based on (current_position - last_position) with some significant averaging to smooth over the inherent jitter. With that being said, what is the response time of one of your non-differential receivers (the ones that don't require a base station). For that same unit, what are the CEP specs at both 50% and 90%?

Do they output in standard NMEA 0183 protocol or something else?

Sorry for all the questions but I'm not quite close enough to this stuff to be up to speed on what the latest norm is for low-cost GPS engines.

Jon,

When skiing or boarding in current. you want your speed to be relative to the speed of the water. So if the water is flowing in a certain direction at 2 mph and you want to board at 22 mph. the GPS would have to read 24 MPH when you are boarding with the flow, and when you turned around it would have to read 20 MPH for you to get the same speed relative to water flow.
This wouldn't be a big deal when on a lake, but for those on a river (like DJ) where there is strong current this could be a deal breaker.

(Message edited by ldr on November 20, 2006)

To continue what Matthew was saying. It wouldn't be that bad, if you knew the speed of the current. You could just add or subtract the proper amount. However, if you don't know, or it varies (Sacramento River) then it just doesn't make sense.

Robb i was thinking that you could probably turn the unit on and drift for a while to get the speed of the current, and then factor that into your set speed.

But you would still have to change the speed every time you turned around.

now, for slalom, they dont care right? gps speed would be what they want, but for us, its the formation of the wake thats important. given that pp adjusts in .2 or .3 increments, and people seem to use thoes (i.e., you press down once, and the rider is happy), I would think the gps would be a no go on a river. sucks tho, cause I didnt want to drill a hole in my boat, but oh well, aint that big a deal.

Why would it be a no go? The unit is a computer, so program in where you are and where you are going and the current. It can do the math without a problem. Autopilots on both yachts and airplanes correct for "drift" all the time. Not an issue if they put it into the program.

being very specific about my circumstances, it would be a go if the computer could know: where in the river I am, the width of the river and how it adjusts the current, the direction of travel, account for the channel effect in rivers, and be in contact with the lower colorado river authorities computer which gives real time info as to the cfs of the dam that feeds the river.

of course, im anal about my pull

I would like to see it break into the market and then read reviews from users...it is very reasonably priced compared to PP...Im just not real confident in it because it is unproven

I've done some software development work with GPSs, specifically for an aviation application. I can't see how GPS would be effective speed control for Wakeboarding.

1) Takes too long to calculate an accurate speed.
2) I can notice a speed difference of 1/2 mph while boarding. That's equal to 1/4 mph of current. (up river +1/4, down -1/4, equals 1/2 difference)

As I think through the logic of this, I suppose the GPS could learn the current based on the RPM variation between up river / down river. Though, it wouldn't be accurate until you ran the opposite direction. You still have the river width problem dj mentioned and what if you're running 45 degree angle to the current?

The river I wakeboard in runs at about 5 mph during spring run off. At 23.5 MPH GPS (ground speed), that's 28.5 MPH (water speed) up river, and 18.5 MPH down.

KevinL, tell us more about your GPS's.

I was at the pro tournament when this system made it's debut (Diablo Shores). I spoke with a friend who drove one of the boats using the system to pull skiers, this is what he told me:

"At the moment the system will not work on any older boat that does not have the latest ECM and drive by wire because it only interfaces with the ECM, no additional cables or servo's, it tells the ECM what it wants and the ECM makes the changes to the fuel & ignition system to produce the desired output"

"The system is extremely easy to use, all you need to do it tell it where the slalom course is by programming the set points at the beginning and end gate bouys"

"The system is great, because it automatically makes adjustments for skier and condition changes"

When I asked him about using the system for non-slalom course applications he said the system is targeted towards competitive skiing where the important thing is the skier speed relative to the fixed bouys or jump. Things like wind, current, boat load, skier weight needed to be adjusted on the perfect pass because they would impact the boat's relative speed to the fixed objects. Using GPS eliminates the need to make these adjustments for slalom skiing.

To make the system adjust to water flow (wake) it will require an additional input from a water based speed sensor, most likely the paddle wheel. This will accomplish exactly what Karl is describing as drift in his post above.

My buddies new X45 has the MC speed control that operates based on RPM and paddle wheel (throttle by wire). It seems to lock in and hold the speed better than my perfect pass. I would expect the 2007+ speed controls to operate much more accurately than anything that is not drive by wire once they get the minor issues resolved.

Theoretically it could know where you are and what the current is already unless it varies significantly. On our mtn lake I doubt it could get a decent reading so it would be a no go for every situation.

As for the "skier", thats Andy Mapple on their homepage, and is probably the greatest skier of all time. He's the brains behind the idea and has always been a major proponent of advancement of all watersports. I don't think this industry could find a more dedicated guy to start up and make a company successful.

Oh yah, he's kinda the guy that teamed w/ Herb O'brien to start up Square One (aka, Radar skis, Ronix wakeboards). This guy is a legend.

Paul, here is a link to one of the brands I sell. They are more aimed toward high precision applications, than consumer grade products. There are probably plenty of cheaper options.

http://www.leica-geosystems.com/corporate/en/products/gps_systems/lgs_4224.htm

You guys really need to take up barefooting, barefooters argue the speed question all the time. We ski between 37 and 50 mph most of the time and we can feel the speed with our feet and know if the driver is giving us 41mph or 41 and 1/2mph. Just get used to varying speeds because that is how it is at tournaments...you won't get what you call...count on it and then deal with it. No boards of any kind in my boat.