Android Start Line Apps Anyone?
Printed From: Yachts and Yachting Online
Category: Dinghy classes
Forum Name: Dinghy development
Forum Discription: The latest moves in the dinghy market
URL: http://www.yachtsandyachting.com/forum/forum_posts.asp?TID=10726
Printed Date: 18 Jul 25 at 6:47am
Software Version: Web Wiz Forums 9.665y - http://www.webwizforums.com
Topic: Android Start Line Apps Anyone?
Posted By: polc1410
Subject: Android Start Line Apps Anyone?
Date Posted: 24 Feb 13 at 10:51am
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I was wondering if anyone has used any of the Android Apps for their dinghy starts. I have an old android phone that broke its aerial so it is no use as an actual phone but is still perfectly usable as a mobile computer device... Just needs a waterproof case which I can get for <£20 I'm on my third sailing watch and am frankly unimpressed by any of them! I like the Novasail that often advertises on the left. Looks like a suped up Tactic Compass in terms of functionality. So several questions: 1. If a class doesn't exclude them are electronic aids like this race legal or do they need included in class rules specifically? (Using GPS, clock and compass basically. Not using the phone signal I know the rules on mobiles). My class rules don't even mention a compass. 2. Anyone got thoughts on the best apps? - I've found Sailing Tactitian Free (looks OK, shame it only lets you have 3 bouys). Start timer, start line using GPS, next mark, and tacking compass. Colour coded background. - SailRacer.net. Start time, start line, lots of marks (good for club round the cans). No tacking compass. - The final count down - think the clock is too small - Yacht - Nice big screen. Colour coded background. Start line. Speaks time instead of bleep (doubt i'd hear the words clearly on boat?) Doesn't remember default count down (my club uses 4mins not 4 mins) 3. If no use as a race tool, any use for training to learn where I go wrong? 4. What about battery drains? Will I get a full day sailing on a phone charge, bearing in mind I'll need to disable screen lock etc as the waterproof case will block access to power button! 5. Where best to mount it? Mast? Bouyancy Aid, Centreboard case, etc? My observations of why I don't like the three race watches I've tried: Optimum Time OS 1 series: Not bad - this one still works I think! Issue is the sync feature is hard to press as its a side button. Optimum Time OS 2 series: Sync button on top. Actually was OK. But leaked. Optimum Time OS 5 series: This had SO much potential to be great. But is abysmal. Its died - new battery brings it to life for a day or 2 at most. If you go into race timer mode and are waiting for the warning signal if you wait more than about a minute it goes back to normal clock. Gun goes, you press start and it doesn't start. Comes with a clip to attach to boat. Broke off on 3rd tack in first race. Watch is waterproof and does float! One of the OS1 and OS2 has very sticky buttons. |
Replies:
Posted By: RS400atC
Date Posted: 24 Feb 13 at 11:33am
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Let us know how you get on, but I doubt you'll find the GPS or compass accurate enough to be very useful on the startline or to spot windshifts. If power is a problem, you could put an external supply in the box, USB is just 5V, a regulator from a few NiMh cells should be easy to do or you might find somrthing on eBay? Personally I am very happy with a tacktick compass and a casio £15 watch. Mrs Crew has an optimum time watch which has worked fine for some years now. I go sailing to get away from electronics and software. |
Posted By: andymck
Date Posted: 24 Feb 13 at 12:53pm
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I used to have a big yellow optimum watch. But the puck fell out. Was otherwise an excellent timepiece. I then tried several of the smaller optumum watches which are not cheap. They either broke or I had battery issues. I was not the only one in my club to have theses issues. Some have sent them back. I have gone back to the tried and tested Casio route. With the tac tic when sailing in open water. The only issue with the Casio is getting the strap over winter gear. ------------- Andy Mck |
Posted By: polc1410
Date Posted: 24 Feb 13 at 1:22pm
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Thats the impression I've had - the orginal big yellow is good. The others seem poorly designed by someone who's never sailed a dinghy! Are your casio's doing a count down or are you just hitting go and starting on the 5 minute? there is an advantage to the bleeps in the last 10 seconds as you don't really want to be looking at the watch... Waterproof case ordered. Season starts for us in 2-3 weeks - will post some feedback. Hope my potential transgression of class rules wont start a 55 sailnumber type debarkle! |
Posted By: andymck
Date Posted: 24 Feb 13 at 1:42pm
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Casio one has fully functional sailing timer. Just doesn't have the synch button. ------------- Andy Mck |
Posted By: RS400atC
Date Posted: 24 Feb 13 at 2:48pm
TBH I've been just looking at the seconds on the Casio for years, I can judge nearly as well looking at the time ticking up towards 11:01:23 or whenever the start is, as with a countdown timer. For big events I sync the seconds with the first gun of the day, or a gps. The crew uses the OT watch, stops me being a minute out. I'm not great at starts, but watches are not my problem. The OT we have is a small blue one, it's been fine, I would replace it with the same. Having the wife/crew to read it for you is good too! The tactick will of course do the 5-4-1-go thing for you. Personally i don't want beeping in the last ten seconds, I normally know I've cocked it by then! |
Posted By: rogerd
Date Posted: 24 Feb 13 at 2:48pm
On my fifth Casio now wish they would make the straps stronger.
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Posted By: Windermere Drifter
Date Posted: 24 Feb 13 at 3:34pm
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I went through about 5 Optimum time watches before I eventually settled for my money back.
If I wore a fleece, when I took it off - the static electicity would effect the watch - usually making the screen go blank, or freeze. They said they had never heard of this before. Is it just me that is fizzing with super high static that only effects Optimum time watches? ------------- WMD |
Posted By: polc1410
Date Posted: 24 Feb 13 at 4:24pm
we usually gount 30, 25, 20, 15, 10, and either its obvious we are a mile out and counting not necessary or we are deseperately trying to hit the breaks and we may then count every second towards the end in that hop we aren't over. I guess one of the advantages of the GPS knowing the startline will be we might at least know if we are OCS as I suspect we get over cautious and go back, esepcially for club house starts where you just get booted rather than tooted!
Think my tight scottish ness is really trying to create a tactic from my old broken phone! |
Posted By: polc1410
Date Posted: 24 Feb 13 at 4:26pm
Intriguing. I seem to be quite highly charged - frequently fry myself on metal handrails in shops etc. Drysuit has a fleecy inner... |
Posted By: polc1410
Date Posted: 24 Feb 13 at 4:31pm
Take it you can't replace the resin trap with a 'normal' fabric/velcro style sports strap? Guess I may get one of these as the reserve watch for when the android inevitably shuts down 20 seconds before the start!! |
Posted By: JohnW
Date Posted: 24 Feb 13 at 4:55pm
Fabric velcro straps work fine on Casios. But only any good if you catch the watch before it goes over the side when the original breaks and you still have the watch to put it on! |
Posted By: RS400atC
Date Posted: 24 Feb 13 at 8:06pm
I don't think common or garden GPS will be accurate enough. To tell me whether I'm over or not when it's not blatantly self evident would be a matter of half a boat length? When you add up the errors in getting the postition in the first place, plus the GPS error approaching the line plus the time delay in the GPS, I think you will find it's nowhere near that good. Try it on dry land. I know my GPS is quite old now, the newer ones are better but how much? Don't be fooled by things like TomToms, they cheat, by assuming you are on the nearest road, as well as doing some clever stuff assuming you are travelling in a sensible way. Differential GPS would do it of course. |
Posted By: polc1410
Date Posted: 24 Feb 13 at 8:40pm
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Thats an unknown to me too as to how good they'll be. In a clear open space
they are good to at least 3m provided they've managed to get a decent fix and from my experience potentially good to
1m! Not sure what happens when you add other masts but at least there
will be no buildings or trees. But from experience on land using GPS if the sky is clear of obstructions you can usually place it on the ground mark a MOB walk away 100 yards and return and the MOB will be marked spot on to about 30cm. My preferred ap based on playing on the sofa is Sailing Tactition (sailingtactition.com) -   It will tell you how accurate it thinks it currently is on one of its screens. From what I've seen the count down flashes red if it thinks you are OCS (I could be wrong) - My issue is usually the last 3 or 4 seconds when I start to think I am over, but I can't see the pin or the RC because other boats are obscuring my view. I can see me outside playing in the dark with it tonight looking like a prat! |
Posted By: polc1410
Date Posted: 24 Feb 13 at 9:43pm
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Hard to know if sailingtactition is warning of OCS - the accuracy of GPS in my street was 12-24m Switched to sailracer.net for a play and if it had accurate GPS it would definately tell me how far behind the line I was (maybe not how far OCS) but how slow I was crossing the line! It also lets me have more than 3 marks and the coollest bit is it will upload my track to their website and let me replay the race (with other boats if anyone else was brave enough)... ...it will take uploads of gpx tracks from any gpx compatible device. Their site shows pictures of dinghies and the demo track is 470s. |
Posted By: RS400atC
Date Posted: 24 Feb 13 at 11:24pm
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You have to be aware that when a GPS susses you are still, it will do some averaging to improve accuracy. There is a lot of clever processing that usually works, but may not be right in a dinghy. For instance some GPS algorithms know that most city streets run E-W or N-s and cheat a little. Works well for the intended purpose, not so good out of context. |
Posted By: RTFM
Date Posted: 25 Feb 13 at 1:56pm
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How accurate is GPS you may ask? Turn on any GPS receiver and it will give you an approximate horizontal position of 10-15 metres. It does depend on how much positional averaging the manufactures GPS unit does, and if you moving or not. Accuracy is also affected by a number of other factors, including the satellite positions, noise in the radio signal, atmospheric conditions, and barriers to the GPS signals, such as sails and masts. However having a receiver that is accurate to approximately 10 metres is not an issue with the race sailing application, as the 10m accuracy stated above is the absolute position, and not a relative position accuracy. All of the sailing boats within the same race area will have the same GPS errors in there calculated horizontal positions. (The largest error is mainly attributed to the ionosphere & troposphere delays as mentioned above). This can be seen by taking two GPS receivers on a single boat (with the same GPS logging configuration) and the ‘base line’ distances between them will remain reasonably constant. ------------- Nobby. |
Posted By: RS400atC
Date Posted: 25 Feb 13 at 8:05pm
That makes an awful lot of assumptions. Two gps receivers on the same boat will have similar inputs to their averaging. To get relative postions with any great accuracy, you have to make sure the receivers are prioritising the same satellites. That is how Differential GPs gets much better accuracy. You have a data feed from the reference receiver sharing info about every satellite it sees. They also often have inertial data too. A good surveying GPS would put you in centimetresof the line, if you were moving steadily. Personally a GPS system that assists me in being 10m behind the the line is something I can live without. And even that 10m or whatever is not a maximum error, it may be 66% confidence or even less. It's fine for generating a tracking plot to feed to spectators or the media, but of limited use to the sailors themselves. |
Posted By: polc1410
Date Posted: 25 Feb 13 at 9:13pm
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not sure if they are reading the GPS direct or just the possition. One of them (I forget which) seemed to be doing lots of very fancy stuff with pitch and yawl etc. If I was writing the basic GPS algorithm I'd tell it to work out where it should be based on speed and direction travel. That may cause some issues as I almost always tack near the line! RTFM wasn't suggesting you'd be 10m behind (or over) the line. But that it would be able to take you back to the same spot on the same day. The way you configure the start line is to sail to the committee boat and stop with the committee boat about 1m to your starboard side. Hit the RC button and set its possition from the GPS. Then sail to the pin and repeat. So it doesn't matter if the global possition is 10m out provide it stays 10m out for the rest of the day. (Although it'd make me happier if I can save some of the fixed marks for eternity but they will also move a little in wind etc.) |
Posted By: RS400atC
Date Posted: 25 Feb 13 at 10:03pm
I think you will find that worked a lot better with Decca. GPS has random errors of the order of 5 to 20m. You can take the same gps back to the same point and be at least 5m out, unless you allow averaging over a few minutes or more. If you have a pure civilian GPS which is reliably better than that, there is a big market for it. |
Posted By: RTFM
Date Posted: 25 Feb 13 at 10:22pm
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>>To get relative postions with any great accuracy, you have to make sure the receivers are prioritising >>the same satellites. That is how Differential GPs gets much better accuracy. Not quite correct. If I may explain... Differential GPS involves the cooperation of two receivers, one that's stationary and another that's roving around making position measurements. The stationary receiver is the key. It ties all the satellite measurements into a solid local reference. Remember that GPS receivers use timing signals from at least four satellites to establish a position. Each of those timing signals is going to have some error or delay depending on what sort of perils have befallen it on its trip down to us. Since each of the timing signals that go into a position calculation has some error, that calculation is going to be a compounding of those errors. Luckily the sheer scale of the GPS system comes to our rescue. The satellites are so far out in space that the little distances we travel here on earth are insignificant. So if two receivers are fairly close to each other, say within a few hundred kilometers, the signals that reach both of them will have traveled through virtually the same slice of atmosphere, and so will have virtually the same errors. Differential GPS can eliminate all errors that are common to both the reference receiver and the roving receiver. These include everything except multipath errors (because they occur right around the receiver such as masts and sails etc) and any receiver errors (because they're unique to the receiver). That's the idea behind differential GPS: We have one receiver measure the timing errors and then provide correction information to the other receivers that are roving around. That way virtually all errors can be eliminated from the system, even the pesky Selective Availability error that the DoD can put on if they so wish... Hope that helps...
------------- Nobby. |
Posted By: RS400atC
Date Posted: 25 Feb 13 at 11:25pm
Yes, that helps me see that you don't really know very much about precise GPS. I suggest you set up a mock start line and see what happens. Any time spent on Android apps could be more profitably be spent I think. |
Posted By: sargesail
Date Posted: 25 Feb 13 at 11:27pm
Indeed - even differential GPS can involve two moving receivers.
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Posted By: RTFM
Date Posted: 26 Feb 13 at 7:50am
| So what part of my Differential GPS explainiation do not understand? In did not say anthing about precise GPS - that's RTK which I assume you also no nothing about... |
Posted By: RS400atC
Date Posted: 26 Feb 13 at 5:10pm
I was using precise GPS in its general sense, not in a proprietary sense. I wouldn't expect anyone who can't spell 'know' to appreciate the difference though. However, let's put all that aside, this is not the place for this discussion. Would you agree that the OP is wasting his time with a simple GPS ap to tell if a dinghy is over the line? |