Zero Off GPS Speed Control

On page 11 of April WaterSki Mag there is an ad for a new speed control system based on GPS; no paddle wheel required.

www.zerogps.com

I am looking at getting Wakeboard Pro PP in the next month or so, so this caught my eye. In the magazine ad it mentions wakeboarding, but from the website you can tell this is aimed at the tournament slalom market. Andy Mapple is one of the developers.

The Pro Skiers on the website say it has more of the feel of manual or human driver, but the same perfect driver everytime who is completely in sync with the rider.

I have never ridden behind a boat with PP. I will be getting this for my son and his pals who are advanced riders and are at a point where they need it. All the other boats they use have PP.

Anybody heard of this and what do you think?

i actually just tested this system in a new boat which had both zero off and perfect pass. the zero off was awesome and once the system was engaged the speed would only go +/- .1 mph at most on flat water. perfect pass is also awesome and i love it but you have to change settings depending on the weight your running in the boat which i dont think you have to with the zero off. besides that they both do the same thing very well, but if i had to choose id probably go with the zero off

I did a little more checking and it's not an option for me with a 99 MC. I think right now it is on option with a new boat only. The boat has to have throttle-by-wire, and for MC that was 2005 and later.

Its supposed to rock for wakeboarding too. NO speed varying in turns and double ups like the perfect pass with paddle wheel does.

I say its only a matter of time before you can retrofit it to any Perfect pass equipped boat....

Call them up and talk to them. Zerooff will probably be AWSA approved next year, so PP will have some serious competition.

They've got a small issue. Speed of the water. This is the age old issue that pilots face. Ground speed vs. airspeed.

Those who board in any body of water that is tidal or a river will agree that you can have quite a flow rate.

Example:
Flow rate = 2 mph (very conservative)
GPS speed setting = 23 mph
Desired speed = 23mph

GPS based boat ground speed into the flow (up stream) 23 mph, net water speed 25 mph.

Result: 2 mph too fast


In the other direction. Again, the GPS based boat ground speed 23mph. But in this direction, the water is helping by pushing the boat and extra 2 mph, net water speed 21 mph.

Result: 2 mph too slow

For accurate water speed, you must measure the true boat speed vs. the water.

-Toneus

also the speed adjustments work in increments of 1/10th of a mph so you can pretty much get the exact speed you want.

Billy,

It doesn't matter how fine the adjustments are if the actual ground speed is not accurate.

As kids we all tried running up an escalator coming down. It didn't matter how fast you ran up, the speed of the escalator coming at you slowed your forward progress. Same thing as driving upstream. The water coming at you will slow your forward travel, which is what the GPS is measuring. Thus it will use more speed to overcome the water flow. Result, you're boarding at 28 mph!

What is the method that the GPS speed control uses to make sure that the speed of the boat relative to the water is correct? Without knowing the speed of the water, it will "never" be accurate. And definitely not within a 1/10.

-Toneus

One more thing. Although, manufactures would like you to think they are. GPS receivers really are not all that accurate.

http://en.wikipedia.org/wiki/Global_Positioning_System#Accuracy_and_error_sourc es

-Toneus

I think the concept is very sound but may not be as useful if you are on a river. Flow rate is not significant on my lakes so I would pick one where I didn't have to drill holes in my boat.
You always wonder about new companies but if they succeed you know PP or a manufacturer will have a version very soon.

first toneus you could just adjust the speed accordingly to get it where you like being on a river if that is actually what would happen but since you or I or anyone else probably hasn't tested the system on a river and until so you shouldn't make assumptions.
and secondly i do feel the gps did a great job keeping the boat at speed. all that i cared when riding was for no change in speed no matter what so when i would cut into the wake evrytime i would know exactly what the wake would be like. when riding with the zero off the speed was dead on the entire time.

anyways toneus i could care less about your problem with river riding and secondly you haven't testsed the system like i have so you dont know what your talking about. im just giving my opinion based on how the system worked when i was riding and with over 3000 lbs of weight in the boat the system did exactly what all riders look for behind a boat, a consistent accurate pull

I was able to see this new system first hand while riding last month at The Boarding School. Shaun's boat had full factory ballast/ 4 or 5 sacks full on top of that and 6 poeple. The speed control worked great! I was impressed. With that much weight in the boat, it held speed better than Perfect Pass.

its good to see some one giving their opinion that actually has some experience with the system

big deal , you make an adjustment for the current. not exactly difficult. with PP you have to do the same for wind and weight.

Billy what boat did you test this on. Looks like it is only available for DBW boats.

I agree with Toneus
For those riding on a body of water with current I think perfect pass would be better. If your riding gps and you are going up and down a river, you are going to have to change speed constantly.
Also, in the three boats we've owned I've never had to adjust PerfectPass for wind and weight

It does sound like it works well for those riding on lakes. And i hope it competes well with PerfectPass to drive down prices.

I don't board in a river either. I'm not bashing the system, or you dude. If you review my posts, I'm pointing out that no matter how great gps is, it's not perfect. I love gps myself. I have three receivers (one aviation, one on the motorcycle/boat, and one in the car).

I also asked a question, which you ignored. "What is the method that the GPS speed control uses to make sure that the speed of the boat relative to the water is correct?" I'm seriously interested in the answer. If they have something that deals with the issue, then GREAT!

You're claiming constant speed control to within a 1/10th of a mph. Sorry, with the technologies involved (gps satellite signal accuracy, speed of calculations, gps calculation averaging), it's just not possible. That is a fact.

I only mention the tidal component because the California Delta (one of the top waterways for boating in the nation), is tidal. That means that all of the Delta waterways constantly have a current. Sometimes in, sometimes out depending on whether the tide is coming in our going out. People who boat there know this, and are aware of how swift the current can actually be.

Sure you can adjust. Sounds like a lot of work for a system that claims to be perfect to 1/10 mph. Doesn't sound so perfect to me. Just an opinion, ignore it if you would like.

DISCLAIMER - I like my PP, but I'm not against new products that might do the job better. With that said.

Rod, you don't have to make an adjustment with a PP for wind and weight. When this is done in competitive events, it's so a timed pass can be achieved. http://www.iwsf.com/rules2004/rulebook2004/rules06v1.0.htm#10.07

"(d)The Boat Judge and the Driver shall jointly agree on the setting of the speed control and the allowed adjustments for wind conditions, etc., with the goal of having the machine produce actual times for each pass."

A PP measures the speed of the boat relative to the water it's going through.

If you would like to discuss physics or the technologies we can. Because those are the facts, and forces at play here.

-Toneus

I just looked on their website and with the limited info they have there it looks as though their cruise model may be comparable to PP WB Pro, It says the cruise uses a Paddlewheel and RPM, It also looks like it uses a digital readout for their cruise and it's only $690.

Any idea if they are going to make this system for non drive by wire boats?

first the system never claimed speed to 1/10th. from my experience that is how accurate i felt the system to be.

there are 3 gps recievers on the boat i believe. maybe you think gps isn't very accurate but im pretty sure speed based gps has been tested to be extremely accurate.

and secondly i dont really care how the system works or wether or not people think gps isn't accurate. all i know is that the system works awesome and thats all i care about and im sure thats what other riders care about as well.

my friends boat which is a new 2007 model has the zero off aswell as perfect pass wakeboard pro and everytime we have gone out on it we have used zero off. i love perfect pass also and im sure it would have worked awesome as well but it shows that zero off which is a new system has its stuff dialed in pretty well to compete with PP which has been around for a while

Why did your friend order a boat with Perfect pass and Zero Off?

Billy,

You are taking this the wrong way. I am simply bringing these items to the attention of others so they can make an educated decision. Like Matthew, I hope they become competitive with PP. That would be great for us as consumers.

Looks like someone else brought up these same concerns.
http://www.tmcowners.com/teamtalk/showthread.php?t=14916

I can tell you from research and experience that a GPS cannot get you to the level of precision that the Zero Off marketing is stating.

If they say they have 3 receivers, it is that they are receiving signals from 3 satellites. 3 is the minimum to get triangulation. Check the gps in a car, it is probably a 12 receiver unit. This allows for more accurate triangulation. BUT! Even with 12 satellites being tracked and triangulated, you will notice that the error is rather great. The GPS will show this error to you. It's the circle around your position on the map, or the number on the satellite signal page. The gps is telling you that it thinks you are somewhere within the circle. The size of that circle will change constantly. I have seen where the circle is as large as a 50' radius. That means it thinks you are somewhere within a 100' area. That's a lot of distance when you are talking about 25 mph.

Some guy has done a whole lot more research on the topic. Feel free to check it out, but it will probably make your brain hurt, it did mine. http://users.erols.com/dlwilson/gps.htm The basics are that a consumer gps will have horizontal error as great as 4 meters or more. GPS receivers only recalculate speed as fast as the processor inside of them can work. I think you will find that a good GPS will recalculate every 1 to 2 seconds.

When it comes down to maintaining perfect speed, one of the biggest issues is the lag time after the speed has been determined. It's the time in sending a signal/throttle movement to the engine, and then the lag time of the horsepower coming in, and then the delay in thrust being transmitted to the water from the propeller. And thus the increase or decrease in speed. Same reason that when you "Hit It", you aren't immediately going 25 mph. Water is a bad medium to accept the pressures of acceleration, and it takes time to overcome.

Correct me if I'm wrong, but you're having to adjust your PP for wind and weight because you're using RPM to maintain speed, not mph. I understand what you're saying.

Is it warm out yet? I need to get in the water. Don't throw some crap about a dry suit, I have one. A heater jacket and shorts too.

Cheers gang!

-Toneus

Everything Toneus has said is perfectly accurate and well educated.

I ride in the Columbia and Snake Rivers, at times the current reaches 7MPH. If I set the Zero-Off to 24MPH, then my downstream waterspeed is 17MPH. Whereas my upstream water speed is 31MPH. Between myself and the water that's a 14mph variation.

I'll agree with you that in a waterway with minimal current, Zeroff is probably killer device.

However, I'll stick to my Perfect Pass since inherent to it's design it compensates for current speed.

toneus, first of all im prety sure you are talking about gps navigation calculating speed.
i dont know much about how gps works but all i do know is that this system is very accurate in speed control and i personally dont care how the system is able to do it.

you keep saying its impossible for it to hold an accurate spedd blah blah blah... well have you tried the system first hand? let me answer that for you. NO.

my friend is a professional rider and i am just as picky as him on speed control being precise. we both felt the system was great. im just telling people my experience with the system and how pleased i was with how accurate it was. wether or not you think gps can be this accurate or not i think a consumer that has used the product first hand would know how accurate the system was.

Whatever...

I tired to be cool about the discussion.

You said it yourself. You don't have a clue about the sensitivity and accuracy of GPS. Under perfect conditions, a pull behind the PP WakeboardPRO would be just that. Perfect! And if it was the first time you rode behind that system you'd be screaming from the roof tops about it too.

Go take a physics class to exercise your brain and then you might understand.

I'm done dealing with you. You're just arguing with yourself at this point.

-Toneus

Toneus is just trying to bring up a point. Anyone in a river would get screwed with this item if no one told them about it. I ride on both rivers and lakes, so it would be out of the question for me.

GPS is as accurate as they say. I have 4 systems on my heavy equipment and they are accurate to .1' (one tenth of a foot) in all 3 axis while running. It uses survey grade GPS. I don't have a Zero Off unit, yet, but my understanding is the technology is the same.

River current varies dramatically from the surface to the bottom. The surface current is not constant and PP must be set to avoid reading the variations in the current. Most of the time, the standard setting do not "read" the current variations and create a "nervous" condition where the PP is constantly correcting. This can be the case in rivers that have uneven bottoms and a lot of eddies and roils. While a river may have 6 mph current, the surface current may vary from nearly stagnant to over 9 mph, depending upon the bottom and banks influencing the area. As I understand the GPS technology and programming in the Zero Off prototypes, you can set for a frequent riding area and compensate for this effect. I don't know if this made it into the production units, but it can be done with programming.

Hopefully, I will be able to answer these questions by experience soon. Right now, my post is based upon derivitive knowledge.

Karl,

Cool, but your Survey grade GPS equipment costs ~$20,000. And that is because it is highly sophisticated electronic equipment. NOT a consumer grade recreational GPS.

http://www.igage.com/thales/c_vs_m_gps.htm#accuracy

You are talking apples and oranges here.

That's like saying my 19ft run about can put out a killer wake that will compete with a professional tow boat.

Face it guys. You are wrong.

PS - It's surface current that is important because that is what the boat hull is interacting with exerting force upon at given speed to create a certain size wake. That Billy wants to be the same at all times.

Will you be happy if we all go buy a Zero Off speed control?

Serenity now! Serenity now!

first of all im not trying to get peopple to buy this. i dont even know if i would buy it. im just lettig people know about this system. as much as love my perfect pass the adjusment of settings due to variance in weight bugs me and was letting people know how well this system worked.

There is a lot of bad information in this thread.

If ZeroOff is delivering their product for ~$700, then they are using a premade $40-$120 GPS receiver circuit. No 1cm accuracy here.

Even if we were to assume the GPS is perfectly accurate, there's still the question of ground speed verses stream speed.

I don't know what's wrong with Billy's Perfect Pass, but I've never had any problems with my PP Wakeboard pro running zero ballast to 4000lbs.

Craig look at their site. When i said $690 i was refering to their paddlewheel/RPM based cruise model. Their other systems seem to be priced somewhere between $1200 and $1600.

Billy is really starting to bug me about the adjusting PP for weight. It just doesn't make sense. That is unless he's secretly a skier and runs his PP in RPM mode.

http://trl.trimble.com/docushare/dsweb/Get/Document-271964/022501-076_RecreationalversusProfessionalGPS_WP_1105.pdf

A great link for rec grade GPS and Professional grade GPS. The distance differential was quite significant.

on my perfect pass unless you change the sensitivity and stuff like that the perfect pass wont engage properly or hold speed very well

Maybe that's the problem, you keep messing with the sensitivity.

In all the boat's I've ever road behind, no one has ever had to adjust the PP settings for fluctuation of ballast.

The settings on Perfect Pass will need to be adjusted if you add 3000lbs additional ballast----thats what the NN and KDW settings are for---read the manual!

So, to summarize for Rich.
Two people have ridden behind Zero-off and thought it was great.
Most people are not familiar with it but like Perfect Pass.
It's probably not as good if you ride where there is a current.
There is some concern that GPS might give inconsistent readings in real life.
It only works currently on Drive-by-Wire throttles.
People like to provide information.
I didn't need to post this.

Just for information Zero-Off have a big backlog of orders so we will have lots of empirical data by the end of summer.

obviously, im not talking about a couple hundred pounds im talking about stock weight versus 2500 lbs...

I contacted Zero-Off 2 days ago via e-mail. I posed the question about Ground Speed verses Stream Speed.

They have yet to respond. Poor customer service?

All you young guys need to take a powder. In my day, you just gave the driver (of an I/O - directs and V's were not around)a thumbs up signal to go faster or a down signal to go slower. Once you were comfortable with the speed, you started your run (slalom skiing)and learned to adjust. My kids are so anal about speed that it makes me want to shut the engine off and jump out of the boat. Interesting discussion though.

Toneus is correct, its plain physics. A gps based system would work great on a cruiser but a wakeboat or my I/O with perfect pass (never had a problem with it) would suck in the intracoastal waterway or a river. Not sure how they are going to compensate for tides or water going faster or slower due to say a large rain storm?? Yea how is your gps going to know to compensate for the faster thawing of snow causing the river to be high and running faster? Yes it may be possible to program it for certain currents but how accurate is that going to be compared to a system that KNOWS the water speed right NOW by measuring it.

Hey guys,
Just a thought about ground speed vs. water speed with regards to Slalom runs; How does the IWSF rule book define speed? I have never been in a competition so I do not know the rules at all.
What I am getting at is there are really two ways to define the speed you are running a course.

1) Speed in reference to the course (ground speed), what the skier feels as time between balls.

2) Speed in reference to the water (surface speed), ie. what the skier feels under his/her ski

Here is why I pose this question. Take the example posed in a river scenario with a 2mph head current. Going into the course with ZeroGPS set at 30mph, your water speed is really 32mph. This would probably feel "fast" to the skier. However, your speed with relation to the course is actually 30mph. So would IWSF consider this a 32mph pass or a 30mph pass. I am guessing the later since many courses also use magnets to verify speed which would equate to speed vs. course.

Take the same example with PP. Would it compensate for the current by pulling you faster through the course. Set it for 30mph and you are actually pulling 32mph over the water to maintain 30mph in relation to the course. Or would it slow down to 28mph (ground speed) so the speed of the water relative to the skier is 30mph.

Just curious. I have PP on the boat we just upgraded to, but have not had the chance to use it yet (bought the boat last fall, can't wait for the spring thaw). Many of the comments above talk about compensating for varying currents. I think this poses a different scenario/problem for wakeboarders vs. slalom skiers. My feeling is Wakeboarders are concerned with surface speed in relation to their board. ie. same pull & same wake. Slalom skiers are probably concerned with ground speed since my gut feeling is that is how IWSF defines how "fast" a pass is. Speed with relation to the slalom course. If I am correct in the assumptions, ZeroGPS (if it lives up to accuracy claims) would be great for slalom but not great for wakeboarders. PP would be the exact opposite. Some food for thought.

I agree with Toneus: GPS is not very accurate on it's own especially if selective availability is turned off. I have experience with the Trimble GPS units since I design them into devices at work. Differential GPS is better (it uses land based tower corrections) but I still think it would have trouble with adjusting speed that quickly especially for under $10,000. Just my 2cents.

Cheers,

LT



(Message edited by coloradonautique on March 22, 2007)

there are exact times for slalom course passes at different speeds, say 32mph, 34mph, etc. It is a timed pass from starting gate to finish gate, with some tolerance built in.

Most slalom courses are not in current situations, particularly any being used in a tournament.

Before speed control it was all done with a stopwatch.

Toneus is absolutely correct. You have to compensate for the river current as a GPS only sees ground speed. I emailed Zero Off on how they do the speed offset but I haven't gotten a reply back. Trade secret, I don't think so as I imagine they would have a button to push while floating and it would then detect speed and direction of the current and the offset would be based on that reading. That would work for that area and time.

Ok, so I'm designing the next generation GPS system for the Air Force. They are adding one new SPS (Selective Position System) signal for civilian use, and another PPS (Precise Position System) signal for the military.

With that said, without WAAS (Wide Area Augmentation System) to augment the GPS signal what Toneus said is COMPLETELY true. WAAS, which has been designed, but not really well implemented helps the GPS receiver, and provides a better fix.

Billy. Just let it go. You like the system, fine. Buy it. Toneus is just letting other's know that it WILL NOT work on a river system. Well it will, but will require constant adjustment. In which case, you may as well just use the throttle to control the speed.

--X--

Has anyone ever heard back from the guys that make this? I called them a few weeks ago and they said they would have an engineer contact me to answer my questions, but I have not yet gotten a response.

Nope, they've never replied to an email but I have got calls back from them. No calls back on the technical aspects or anything other than order info. I've got my name on their list and at the time requested a black bezel. I have not given them any money either, so no worries yet. They did say they were getting an enormous quantity of emails and were awaiting sanctioning approvals.
More Buzz than Business so far.

Thanks for the update. I think the problem with using it on water that has a current may be real, but I really just boat on lakes. I decided not to get Perfect Pass on My Supra 24 SSV because I came across this. Hopefully it works out. It would be nice to not have to drill a hole in my hull for the PP speed sensor.

Mike, I believe that Supra already uses a padlewheel for their speed sensor, therefore all you need to do is plug it in to you perfect pass unit. There is no need to cut another hole.

I e-mailed them over two weeks ago with no response...

If their pre-sales support is this bad, imagine how bad it'll be after you buy the product.

I got a response:

Dear Sir,
Thank you for your inquiry to GPS based speed control and Zero Off GPS speed control. We have taken the liberty to submit your letter to some Capital investors since you feel that you know more about GPS than we do.

Take this as hint to start your own damn company since you know so much.

See you at the Boat Show

Sincerely,
Ima Joking