anchor drag alarm setting dilemma

[Chris_Robb]

If I understand correctly - the phone/GPS identified it was dragging but it was actually stationary (in an office, where reception might not be good) Consequently the drag trigger might be a combination of the 1 minute pings, not being sufficiently frequent or the location was not the best for reception.

With apologies to your long suffering wife - but any chance you can better define the parameters?

I'd do it myself, but as mentioned - for phones I'm a complete Luddite, but willing to be convinced that I need to join the masses - but so far I'm not convinced. I would not mind being woken up if the anchor actually dragged but I would mind being woken up if the alarm was insensitive (to my need for sleep).

But then I might have misunderstood your post

Jonathan

Hi Jonathan

As it was indoors, the phone was not getting a good view of the sky and only getting enough sats for a basic fix, so the accuracy was wobbling to over 70 meters at times - which of course triggered the drift alarm set at 60 meters!

Even if you are a complete luddite - its a free app and got an almost 5 stars from it users. Certainly worth down loading and playing with.

I had one parameter set to beep if the GPS contact was lost - which it was doing every so often - so knowing the reason (indoors) I switched that off. Seems to be a well thought out job. Not looked at any others though.

I might down load "Drag Queen" just because of its name!

 

[ip485]

Neeves

To establish accurate distances we would use radar but appreciate you might not have it - you then need to guess how close (or far) yachts or rocks might be.

I would be interested to know exactly how you use this technique please? (I dont mean just establish an accurate distance but how you work this with the actual anchoring and then monitoring your drift while at anchor).

 

[prv]

I would be interested to know exactly how you use this technique please? (I dont mean just establish an accurate distance but how you work this with the actual anchoring and then monitoring your drift while at anchor).

I once stood anchor watch on a small ship in a Norwegian fjord. The radar was a desktop-style Furuno unit with a glass CRT; the First Officer drew around the outline of the land on the screen with a grease pencil and said "call me if the picture stops matching up with the pencil marks".

Pete

 

[prv]

I can't imagine your GPS turns itself on and off every minute

I would expect a smartphone app to do exactly that. Just turning the GPS chip on and off, not the whole phone.

(In practice, "off" probably means a very low-power mode that preserves the ephemeris data so that the next start doesn't have to download it again. The subsequent hot-start would probably only take a second or so.)

Pete

 

[Neeves]

My 'fear' is not so much the Apps as the phone. The phone need be 'indoors' (or it will get wet and or you will not hear it when asleep). We, everyone, anchor in sheltered spots, often with a semicircular ridge of land providing the shelter (a Scots loch) - that's why its an anchorage! I can see the GPS working on the open sea, nothing to obscure any of the horizon. Are phone GPS sufficiently sensitive to offer reliability.

Sorting out how long the battery lasts is critical as is how do you use the various apps to best advantage - the 'work' needs to be done - but I'm interested in my fear of sensitivity as if the phones do not work in well sheltered anchorage - then its all a bit academic and maybe generates some complacency.

But there-again - does anyone use only a phone (or tablet) for navigation and has no fall back to an old fashioned chartplotter?

Jonathan

 

[prv]

Are phone GPS sufficiently sensitive to offer reliability.

Phones use newer, better GPS receivers than most marine kit. I have a classic Garmin 128 among the other nav gear on Ariam, state of the art circa 1995. It sounds like you'd trust that more than my iPhone that benefits from two decades of fast-paced technological improvement since then - if so, that's completely illogical.

Sorting out how long the battery lasts is critical

Why? We all cart around vast (by phone standards) banks of 12v lead-acid batteries, so there is no reason to worry about the phone's internal battery. 12v chargers are peanuts on eBay.

Pete

 

[duncan99210]

I've been using an anchor alarm app on either smart phone or iPad for the past three years, anchoring about 100+ nights a year. The first app was prone to false alarms but the iPad app uses an averaging system which looks at a series of fixes and does not alarm until the average value exceeds the set limit. I've found it very accurate and it's never generated a false alarm so far.
The anchor point is determined by you telling the app how far away the anchor is and at what bearing. You can also set a guard zone to take account of any fixed obstructions you need to avoid. Battery life is shorter than normal but I have fitted charging outlets in the salon and by my bunk, so that's not a concern.
I never even considered running the chart plotter alarm. It's too quiet for me to hear and in any case guzzles electricity in comparison with the iPad.

 

[pmagowan]

I use my phone, plugged in to the cigarette lighter socket. Never had it fail but then I have not dragged. It certainly makes me feel more comfortable.

 

[Neeves]

Phones use newer, better GPS receivers than most marine kit. I have a classic Garmin 128 among the other nav gear on Ariam, state of the art circa 1995. It sounds like you'd trust that more than my iPhone that benefits from two decades of fast-paced technological improvement since then - if so, that's completely illogical.

There was no suggestion that I'd consider your Garmin 128 as being anywhere near the accuracy of a phone, in the same way I do not think my Pronav 100, circa 1989, is in any way as accurate as your Garmin 128. I actually cannot see where you got that idea. Maybe be a bit more realistic (and useful) - how does a current phone GPS compare to a Simrad NSS or B&G Zeus?

Equally I'm not sure why you quote lead acid batteries. Most people want to have their phones within reaching distance (which might be a long way from the nearest 12v socket), after all is that not one reason they are called 'mobile' phones , so that if it rings they can answer without getting out of the berth - so knowing how long the battery will last, with an anchor alarm running, seems a pretty useful bit of information to me.

Jonathan

 

[sailaboutvic]

The odd false alarm guys isn't a bad thing , it keeps you on your toes .
I have used anchor watch by Luky Soft for two years now , I found on my iPad it works well , battery last throughout the night without a problem ,
It lies next to me on the forwards bunk and if it goes off believe me you hear it , you have to be almost out of this world not to .
So far I have not had a problem with it not picking up a GPS .
You can set your Lat and long at a later date if you want , or just press the anchor button when you drop it .
Best part of setting the lat and long afterwards is , if you take note of you lat and long while dropping , if some thing goes wrong ie the iPad stop working or the app or you anchor drag a bit before setting , you can set it again .
It will send a text to another phone or an email although I not sure I want to be on a bus some where and know the alarm gone off .
It could useful as a tracker , I expect if you leave your boat on a Harbour or Marina and went home , it would then act as a safely device but you would need to have the phone iPad on charge full time . Once set I alway give it some leeway so it don't give me false Alarm although it has happened , I expect a lost of GPS for a second or two .
It will track the boat while anchored so you can see what's happen while anchored.
Most of us hate buying some thing then finding faults and won't running it down , but that become no help to anyone ,
I found this app works well , people who have also brought it have been happy with it too , I have used other app in the past but so far found nothing that bet this app for me .
Good luck with what ever you use , in these days of app I think using some thing is better then using nothing even if you get the odd false alarm

 

[GrahamM376]

But there-again - does anyone use only a phone (or tablet) for navigation and has no fall back to an old fashioned chartplotter? Jonathan

To many, a phone is just a telephone and tablets are things doctors prescribe. Having tried navigation on PC I still prefer paper charts but do have a stand alone plotter for when I feel like using it.

 

[DannyB]

I use Drag Queen on my iPhone, press the anchor position button as I drop the hook, then once it's dug in, give it some welly in reverse, and note the distance from the anchor. That's the distance I use for the alarm, once I shut the engine off, the chain catenary pulls me back towards the anchor. The phone is plugged into the charger all night in the cabin with me, so if it goes off I'm going to hear it. So far it has worked for me.

 

[ShinyShoe]

With apologies to your long suffering wife - but any chance you can better define the parameters?
[/quotye]
Thats the windowsill problem. Its got a view of about 25% of the sky.
If you take a smart phone outside and sit it on a level surface you'll get a position with an accuracy reported by the sat system as <10m fairly reliably. Steady for long enough with absolutely no obstructions you'll get 3m.
You'll get 10m no problem on a boat through fibreglass.

I'd do it myself, but as mentioned - for phones I'm a complete Luddite, but willing to be convinced that I need to join the masses - but so far I'm not convinced. I would not mind being woken up if the anchor actually dragged but I would mind being woken up if the alarm was insensitive (to my need for sleep).

If you are going to have a GPS alarm and don't want to use your plotter to do it then this is definitely a decent option. You don't need to replace your existing brick phone to do it though. If I said there was a GPS box that for <£35 could be bought and installed on your boat with 24/7 power from your battery. For the addittion of a Free SIM card and paying £10 to top it up once and provided it sends a message once every 90 days will allow remote monitoring. for no more cost provided it doesn't need to text you and texting would cost a standard SMS message or could be FREE depending who your phone provider is. Would you be interested? Oh I forgot to say not only can you set a radius from the anchor you can take out a wedge where you don't want to go. (i.e. rocks, shipping lanes etc) Yes? Well you can do all that using this off the shelf combo:

http://www.ebay.co.uk/itm/BNIB-BLAC...886363?hash=item25adee9e1b:g:hDwAAOSwcBhWY4hf
+ plus +
https://play.google.com/store/apps/details?id=com.sjaellsoft.myanchorwatchfree (Pro version may have a fee in future, but the most expensive fee is ~£10 and I'd bet you can find suitable for less than £5).
+ plus +
https://www.giffgaff.com/orders/affiliate/shinyshoe

Of course you can set it on a mooring or in harbour/marina when leaving boat and it texts you if for some reason your boat moves...

" I assume therefore than the once a minute ping to the satellites is fairly important in that lack of consumption."
I can't imagine your GPS turns itself on and off every minute, so possibly it only compares the positions every minute?

Software configurable setting, designed to save battery. But on board on charge not usually an issue. BUT if you are charging from a 500mA USB port it may be drawing more than its able to replace. A 2.1A USB will usually be fine. A saving mode may compromise nicely. (There is an android ap called Ampere which will help you understand whats going on.

 

[Neeves]

ShinyShoe,

Lovely detailed and easily understood post.

The phone I use was bought as it is what is described here as a bush phone, its a big country and Telstra have a few phones that give greater coverage. They are focussed at people who live inland, say on massive farms, but they are ideal for marine application and we get almost 100% coverage right round Australia, there are a few gaps, but not many. I can cross Bass Strait and get coverage for all but a little 40nm circle in the 'centre'. When we bought they did not have Andriod phones with this facility - but I note that has been overcome and I could join the rest of the world when I need to replace. In the meantime I call fall back on your option.

Very many thanks.

Jonathan

 

[noelex]

It is important to centre the anchor alarm directly over the anchor.

The easiest way to do this accurately is to use the trace of the track when dropping the anchor. Usually the anchor drop point is quite obvious. However it is important to realise that this trace is produced at the GPS aerial's location. To centre the anchor alarm correctly this point needs to be displaced by the distance between the GPS aerial and the bow.

If this is done, the anchor anchor alarm can be centred directly over the anchor. There will be no false alarms with wind shifts. The alarm distance only needs to be slightly greater than the scope.

Unfortunately, this means setting the anchor alarm from a remote waypoint and some chartplotters do not allow this. If a remote waypoint cannot be selected it is generally impossible to set a sensitive anchor alarm in conditions of variable wind direction. The apps for smart phones and tablets all allow the selection of remote waypoint, but the quality of GPS signal indoors is often a little worse. Multipath distortion can lead to more false alarms (or force the selection of a greater deadband).

 

[Thedreamoneday]

Can I ask which app is it you're using?

 

[noelex]

Can I ask which app is it you're using?

Generally I don't use an app. The main anchor alarm is on a Furuno GP-32.

This lives next to bed. It only consumes about 0.2A and gives a nice B&W trace of the boats position.

Others can comment better than me which apps are best, but iDrifter seems very good.

 

[Thedreamoneday]

Generally I don't use an app. The main anchor alarm is on a Furuno GP-32.

This lives next to bed. It only consumes about 0.2A and gives a nice B&W trace of the boats position.

Others can comment better than me which apps are best, but iDrifter seems very good.

Ahhh, don't know what happened there there, the question was for Duncan99210.

Thanks

I've been using an anchor alarm app on either smart phone or iPad for the past three years, anchoring about 100+ nights a year. The first app was prone to false alarms but the iPad app uses an averaging system which looks at a series of fixes and does not alarm until the average value exceeds the set limit. I've found it very accurate and it's never generated a false alarm so far.
The anchor point is determined by you telling the app how far away the anchor is and at what bearing. You can also set a guard zone to take account of any fixed obstructions you need to avoid. Battery life is shorter than normal but I have fitted charging outlets in the salon and by my bunk, so that's not a concern.
I never even considered running the chart plotter alarm. It's too quiet for me to hear and in any case guzzles electricity in comparison with the iPad.