25 replies to this topic

[V-15_Frenchie]

New sailing toy?

http://www.thesailinggps.com/

[ShockValue]

The Sailing GPS is unique in realizing that sailboats often zig-zag to their destination, which affects the distance and travel time.

My chartplotter does VMG just fine.

[tikipete]

http://www.velocitek.com/speedpuck/

[casc27]

Unless that thing has an input for wind angle and can be programmed for your particular boat it's all meaningless. And every gps I've seen in the last decade already has a vmg function. Looks like a solution to a non-existent problem.

[VwaP]

Is it waterproof and does it float?

[Cat sailor]

There is a detailed product review here that clarifies some of these questions: GizMag.com. The Sailing GPS is water-resistant, and as you'll see from the pictures in that review, it comes in a waterproof DryPak (and it does float).

ETA is designed for power boats. Although it is a standard feature on GPS chartplotters, it does not account for tacking distances. VMG has similar problems when you are on a tack. Did you know that if you are on the correct tack going upwind with a constant speed, that your VMG will decrease all by itself the longer you stay on the tack? It will go all the way down to zero, and even into negative numbers. What kind of measure of velocity is that? It is like driving down the highway at a constant speed, and having your speedometer decrease all by itself down to 0. Not a very good measure of velocity.

There is a detailed explanation of how this happens with Velocity Made Good (VMG), if anyone needs geometric proof, in this article (863 k PDF). Or, you can just try it yourself sometime and see it happen on any GPS. Tack to a waypoint upwind, and watch the VMG.

Everyone thinks that because GPS satellites can pinpoint your location on the face of the earth, that everything on the screen must be equally accurate. But Tacking Time to Destination (TTD) is a much more accurate and reliable indicator than ETA and VMG.

Finally, yes, The Sailing GPS does have an input for wind angle, and can be programmed for your particular boat. This is explained in the product review above: you can enter the wind direction and speed manually, or it can receive real-time wind data via Bluetooth. There are also some short YouTube clips explaining polar plots on the web site for The Sailing GPS. It is a pretty big innovation: the only GPS from any manufacturer that learns your vessel's unique polar plots. Since it can learn your individual boat speed in all wind directions and wind speeds, and can calculate the tacking distances, it can then display your optimal tacks and also the correct Tacking Time to Destination.

[Total Slacker]

Looks to me like the iRegatta app is more advanced. Polar data collection & smoothing, wind direction input manually or via NMEA wifi from instruments. $10. It may not provide TTD, but it does display laylines and VMG, along with an indicator showing whether you're too high or too low.

But hey, good luck!

[VwaP]

Great so it is not waterproof and does not float on it's own. Might be good for a land yachting if it doesn't get too much dust in it.

[floating dutchman]

And it's better than this how?

http://www.trademe.c...n-464524076.htm

[Cat sailor]

The big GPS chartplotter has a beautiful screen, but it is just a map viewer. It does not calculate your optimal tacks or Tacking Time to Destination (TTD). As noted above, standard GPS chartplotters show ETA. ETA is wrong for sailboats. Mathematically incorrect. ETA views sailboat tacks as cross-track error. It does not account for tacking distances, and assumes you should go in a straight line to the waypoint, like a powerboat. But if it doesn't know the distance you will travel, how can it calculate how long it will take to get there?

The Sailing GPS solves this problem. It is not meant to replace a chartplotter, but it can do some innovative things that are useful in any sailboat, whether you have a chartplotter or not. It can show you whether you will arrive faster by heading more upwind to reduce the distance, or by heading off the wind more to increase speed (but with a longer distance). It will display your exact tacking distances, and can even learn your unique boat's polar plots. Plus, it is pretty easy to use. As those YouTube clips show, you can even just enter the directions of the wind and the waypoint, and from those two buttons alone, it will display the optimal tacking angles.

One last clarification... Like iRegatta, there is also the low-cost SailTimer app from the company that makes The Sailing GPS. This app includes optimal tacks and Tacking Time to Destination (TTD). The next free upgrade is also going to include hydrographic charts, so that the optimal tacks can be shown on a chart overlay. Also, as shown on SailTimerWindVane.com, the SailTimer app can receive wifi signals from the wireless, solar-powered SailTimer Wind Vane.

The iRegatta app relies on you to tell it your tacking angle. That is where it gets the laylines from. So if your guesstimate of your tacking angle is off, it will give you the wrong laylines. Or if you are on the wrong tack, it will automatically tell you to turn by your given tacking angle onto the next tack, which would also be wrong.

The SailTimer software has a proven record, and has also been licensed since 2006 to display chart overlays in the full-featured chartplotter software from NavSim (Windows) and MacENC (Apple).

Bottom line: Sometimes an app is convenient. It is low-cost, and displays amazing graphics on the mobile device you already have in your pocket. But maybe you don't want to take your beautiful iPad out on a Hobie Cat or dinghy sailboat where it is wet and where things are flying around. Or maybe you row a dinghy out to your sailboat on a mooring, and protecting your iPad to even get it on the boat is not so easy. In that case, The Sailing GPS may be more suitable, because it is durable, comes in a waterproof bag, and can be easily viewed in direct sunlight. Either way though, if you are using ETA or VMG on a standard GPS chartplotter, you are not getting accurate, reliable, safe information. Other boats using custom polar plots and optimal tacking routes from The Sailing GPS or even the low-cost SailTimer app will have an advantage.

[Ryley]

First off, buy an ad and show us some tits, newbie.

Secondly, if you're associated with this device, change your wording on the web page. The way it's written now is for sale to the powerboater set. you're really using the term 'zig zag' when you're talking about tacking? If you're trying to compete with velocitek and tacktick, then your audience already has a good understanding of "tacking" and "VMG" and "VMC." Talking down to us ain't gonna get much sold.

Lastly, I tried clicking a few of the links on the web page, like "How it works" and "youtube videos" and the site just spun. If you're serious about selling these things, make sure you're hosted somewhere you can handle the bandwidth. It took over a minute to open the videos page - this does not inspire confidence.

[VwaP]

[casc27]

Eeew, I was eating breakfast, dammit!

[WHL]

Looks to me like the iRegatta app is more advanced. Polar data collection & smoothing, wind direction input manually or via NMEA wifi from instruments. $10. It may not provide TTD, but it does display laylines and VMG, along with an indicator showing whether you're too high or too low.

But hey, good luck!

+1

The description of the Sailing GPS' use fo "VMG" seems to interchangeably mix the concepts of VMC and VMG, but calls both of them VMG.

[CaptJackSparrow]

According to this page VMC has the same problems as VMG.

[casc27]

According to this page VMC has the same problems as VMG.

Yes, but in the text on tha tpage he says: "We may as well go back to fiddling with imprecise plastic gauges and slide-rules". Clearly this person has never actually done any engineering work using a slide rule. They are far, far from imprecise. But it's just advertising copy, so you can say anything...

[CaptJackSparrow]

Good idea. Lets stop using databases, polar plot graphs, automatic calculations, any calculations with more than 3 variables, and lat/long coordinates with decimals -- and we can all go back to using slide rules again with a pencil and paper while we're steering the boat and setting the sails.

Why the hostility, personal attacks, and resistance to better approaches? Unless you are just here because some big company is paying you to criticize any new technical innovations. Let's discuss the actual sailing and navigation.

Isn't it better to use navigation instruments and methods that give correct information? Whether slide rules are precise or not is an irrelevant diversion. But VMG, VMC and ETA are all imprecise for sailboats. This is not advertising hype, it is a mathematical fact.

Both VMC and VMG are bad measures of velocity, since they decrease all by themselves even if you continue on the same tack at the same speed. If your VMC or VMG shows 5 knots, and you have 10 nautical miles to go, it is not correct to assume that it will take you 2 hours to get there. If you stay on the same tack at the same speed and check a few minutes later, the VMC and VMG will be lower. Then it looks like it is going to take you even longer to get there, even though you are closer now. That is not logical and not mathematically correct.

VMG and VMC also indicate that you get better progress if you tack a lot staying close to the rhumb line, which is not true.

Navigation instruments that give better results, are cheaper, safer and easy to use would be good for all of us.

[CrushDigital]

For racing sailors, VMG is a little bit more than meaningless. Talking to all of us like we've never been sailing isn't going to get you very far.

That being said, I think it's funny that someone who is the second sock of a shill for this product is accusing everyone else of being shills for Big Sailing.

[Somebody Else]

I'm very comfortable with the Garmin 72.

I love its interface and I love how the skipper can see my red arrow from across the boat.
I love how I can program the displays to show what I think is important.

I love how quickly it acquires and how it conserves batteries.
I love how robust it is.
And cheap.

I can make that sucker dance!

It would take something along the lines of Expedition on a ruggedized tablet for me to give up my GPS72C.

[Somebody Else]

And to CaptJackSparrow: It's not the tool; it's the craftsman that makes the difference.

[Ryley]

Good idea. Lets stop using databases, polar plot graphs, automatic calculations, any calculations with more than 3 variables, and lat/long coordinates with decimals -- and we can all go back to using slide rules again with a pencil and paper while we're steering the boat and setting the sails.

Why the hostility, personal attacks, and resistance to better approaches? Unless you are just here because some big company is paying you to criticize any new technical innovations. Let's discuss the actual sailing and navigation.

Isn't it better to use navigation instruments and methods that give correct information? Whether slide rules are precise or not is an irrelevant diversion. But VMG, VMC and ETA are all imprecise for sailboats. This is not advertising hype, it is a mathematical fact.

Both VMC and VMG are bad measures of velocity, since they decrease all by themselves even if you continue on the same tack at the same speed. If your VMC or VMG shows 5 knots, and you have 10 nautical miles to go, it is not correct to assume that it will take you 2 hours to get there. If you stay on the same tack at the same speed and check a few minutes later, the VMC and VMG will be lower. Then it looks like it is going to take you even longer to get there, even though you are closer now. That is not logical and not mathematically correct.

VMG and VMC also indicate that you get better progress if you tack a lot staying close to the rhumb line, which is not true.

Navigation instruments that give better results, are cheaper, safer and easy to use would be good for all of us.

ok, so the sliderule is irrelevant. you put it on the shelf with a sextant and celestial navigation (and yes, you *did* call the slide rule imprecise. Your words). The page you pointed at still mixes up vmc and vmg, and also contains correctly spelled but misused words ("Optical" when I'm sure you met "optimal"). The fact is that your "patented algorithm" must *also* reduce the velocity to something near 0 to get the tacking angle to the mark, because as I'm sure you know there is no difference (distance-wise, though hugely in a tactical situation) between banging a corner and tacking up the rhumb line. If your claim to fame is being able to tell us which is the lifted tack when the mark isn't directly upwind, then in software you're doing what most of us already know.

For that matter, I think you're mistargeting your device. It's next to useless for a buoy sailor who also has to take into consideration things like shoreline artifacts, current, and most importantly the position of other boats. It *might* be useful (if you can prove it even works as advertised) for a long-distance racer where the legs are measured in 10s or 100s of miles. Still, I'm leery of anything that claims it can 'learn' the polars of a boat. In any case, I think you'll find that most of us who race, at whatever level, actually DO have a clue as to what we're doing, and DON'T like it when a person, organization, or website talks down at us and then to top it off comes in and gets all snarky. There have been some legitimate criticisms. Tell you what. let's get a couple of vipers out of marblehead. you bring your toy, the other crew will sail their best guesses. you MUST sail the angles it tells you to sail. best out of 3 to the windward mark. you don't have any results listed to back up your claims of superiority, and until you do, expect to be met with skepticism.

[CaptJackSparrow]

No-one is suggesting that seamanship and good judgment should be ignored. However, when it is time to make tactical decisions and judgment calls, you want your instruments to be giving you correct information.

Kind of disappointed at all of the defensiveness, hostility and personal attacks here. We're just discussing navigation methods, from which we can all benefit. Let's keep to the navigation issues, and be respectful.

ETA, VMG and VMC have problems. They are useful conceptually and are great for powerboaters, but the results commonly displayed on GPS's are incorrect when sailing on a tack. There has been no evidence to the contrary in the above discussion. There is widespread agreement from many different sources that VMG decreases all by itself the farther you tack from the rhumb line. For example:
"VMG is not a usable helming function." http://www.ockam.com/funcperf.html
"To a helmsman, VMG always appears to recommend heading up." http://www.ockam.com/functarg.html

Similarly, the common display of ETA on GPS chartplotters does not account for tacking distances. But the correct tacking distances and optimal tacking angles can be calculated. They are used in The Sailing GPS, and have been used under license since 2006 in the popular chartplotter program MacENC.com (also makers of the iNavX app for iPads), and also in NavSim.com's SailCruiser chartplotter program for Windows. If you can calculate the exact distances and time on each possible tack, and identify the optimal tacks, that is going to give you better performance.

Incidentally Ryley, why don't you think it is possible to collect data to learn the polar boat speeds? The Sailing GPS is the only device that does this. But if you look at a polar plot, all it shows is the boat speed, the wind angle and the wind speed -- all data which is readily available. This way you can get actual polar data for your individual boat. That is more accurate than estimates from a velocity prediction simulation, or generic estimates for all boats of the same type from a manufacturer.

[ShockValue]

The Sailing GPS is the only device that does this.

Except for the other ones, like iRegatta and MaxSea, etc.


Nice try making a puppet to defend your original post...

[CaptJackSparrow]

I would consider a GPS device something like B&G's Zeus chartplotter. At $3695 for the smaller 8" version or $4995 for the 12" screen, it is pricy but avoids the challenges of trying to see the iRegatta "app" on a screen outside, or trying to use the MaxSea "software" on a laptop while sailing.

So B&G's Zeus hardware is an example that supports polars, although only indirectly. The Zeus is a display, although storing the polars requires B&G's additional Hercules network CPU accessory ($7,000 - $10,000 extra: http://www.chicagoma...H3000_Price.htm ). That seems to be the closest GPS hardware device that handles polars.

However, unless anyone has any better information about the B&G hardware, even then it requires you to enter your own polar data and cannot generate a unique polar plot for your own boat.

[stranded]

Both VMC and VMG are bad measures of velocity, since they decrease all by themselves even if you continue on the same tack at the same speed. If your VMC or VMG shows 5 knots, and you have 10 nautical miles to go, it is not correct to assume that it will take you 2 hours to get there. If you stay on the same tack at the same speed and check a few minutes later, the VMC and VMG will be lower. Then it looks like it is going to take you even longer to get there, even though you are closer now. That is not logical and not mathematically correct.



MATHEMATICALLY not CORRECT ??????


It is GEOMETRY dealt with mathematically

................. the simple right angle triangle problem is being dealt with in a GPS by using spherical trigonometry



........... and if vmg is reducing, given steady speed and compass course, you are sailing away from the windward mark, and need to tack

this , to me , is the main piece of information I am getting from vmg ( rate of approach to a mark directly to windward)

more precisely, a rate of change of angle relative to the waypoint expressed as a velocity




never heard of the 20 degrees rule of thumb ?


of course, this assumes an open piece of water, with no obstructions, etc.


people who want one display to tell them everything, live with the fairies


P. S.

does that lady use the water to make them grow ?

[yisitalwaysraining]

Capt. Jack:
First, I hope you did not have a hand in creating this device and are simply marketing it for someone who actually has the ability to manufacture something useful but has fallen victim to your idiocy.

That being said, we are all entitled to our own opinions, it appears you have chosen to create your own facts. where to begin......

So if you would bother to understand the Ockam document, you would get that he says looking at VMG is bad because when you head up too much the boat eventually stops (this may suprize you) and that your short term VMG gain vaporizes when you stop the boat because you headed directly into the wind. (and that's the point of targets, which I'll rail on you about in a minute). Also, I fail to understand how, assuming that:
1)my boat can actually go upwind or downwind,
2) I don't suck as bad as you
3) there's actually some breeze, and
4) there's not a monster current against me,
my VMG can ever be zero, as it has nothing to do with a course, as it's relative to the wind direction. Now, if you add a mark in there then what you say may be in fact true on your boat, as I'm sure it's hard to track a mark and hold your dick device in your hand at the same time especially knowing that you only have a single active braincell. Now, when the rest of us sail, and VMC goes nagative (or 0) it generally means it's time to think hard about what you're doing. perhaps a tack may be in order or there are other reasons to continue on this board (current, obstructions, cute bowgirl on the boat next to you etc) but I don't think the device is lying or somehow wrong,

Then there's your polar idea. Yep, great idea, doesn't really work. Polars are supposed to represent your best possible speed at a given set of conditions and given that you just randomly "collect" it as you go you will end up data that pretty much sucks as well. (just look at what iRegatta gives you) sure you can go out witth your best crew and all new sails for polar development sessions, and then use this data. but if you aren't sailing fast to begin with this will guarentee that you stay slow. (oh, we're over 4kts in this shitbox, we better head up to maximize VMG) Now if you were to give me a way to only pick ther perfect data spots and lock those in as your "best ever" (and not because you were simply pinching up to bleed off speed) then it would be interesting, but I''m guessing you're not that smart.

So I could put the $10 iRegatta on a daylight viewable tablet and get a better answer because at least there i can export and edit the polars, and then I can remote desktop over to expedition, and then watch netflix if I'm bored.....how about you?

I'm just curoius, is it hard getting through some days knowing you have so little to work with?

ps. bluetooth sucks for this type of application, at least go to TCP.