Garmin Anchor Drag Alarm

Being a lifelong software designer / developer, sometimes I'm amazed at what people create, or fail to create. When we anchor, my wife is at the helm and I'm out at the anchor platform. I have a wireless remote for the windlass. We have headsets so we can communicate easily.

We have decided where we want to drop the anchor.

There's a MARK button on the Garmin MFD. When I determine the anchor has touched bottom I say "MARK" and she replies "MARK." Then we commencing letting out our scope and setting the anchor.

Yesterday for the first time I thought I'd try the Anchor Drag Alarm. After we set the anchor and shut off the engines, I found the screen on the Garmin 8617. You can see in the picture that you can turn the Alarm on, and set the radius. There's an "Edit" button and a "Recenter" button.

Here is the entire documentation on this screen from the manual:

Setting the Anchor Drag Alarm
You can set an alarm to sound if you have moved more than an
allowable distance. This is very useful when anchoring
overnight.
1 Select Settings > Alarms > Navigation > Anchor Drag.
2 Select Alarm to turn on the alarm.
3 Select Set Radius, and select a distance on the chart.
4 Select Back.


They don't even document two of the buttons, nor do they have any advice on how to use this function.

It seems to me, the center of the circle should be where you think the anchor is located. It seems to me I'm showing Mr. Garmin that, with my anchor mark.

Doesn't it seem like that "Recenter" button would center the circle on the mark? It doesn't, it centers it on the screen.

There's no way to move the circle.

Without luckily floating over the anchor, or starting an engine and motoring to it, it seems the only way to use this functionality is to be ready and hit the mark and turn on the alarm.

Thus far, anchoring is a busy time. We are putting the boat where we want it, monitoring our distance to other boats using the radar, figuring out where we'll end up with our scope, you know how it is.

I suppose this is a minor piece of functionality in the grand scheme of things. I know they are doing amazing work like slaying AutoRouting dragons.

But how fricking hard would this be to make much more useful?

I was on the phone with Garmin today (2 hour call back) about another issue and I asked him about this. Was hoping there was some way to move the circle and I hadn't figured it out yet. I emailed him the picture so we could look at the same thing. He didn't seem to understand why I thought it needed to be improved.

In my software company we fixed little things too. If it isn't right, it isn't right. Why punish users that have selected your product and paid good money?

JustBob, I have never figure out how big the circle should be. PLUS, the anchor alarm is of little good if it wont wake you while you are sleeping. I would think there should be a way to extend the anchor alarm to the stateroom or put a bell on the system so you can hear in in the stateroom.

Just download the Anchor Alarm app to your cell phone. Works better, place the phone next to your pillow when you sleep so you can hear the alarm. Best part of all, you DONT need a cell signal for it to work, it’s working off of GPS, which works anywhere��

Taras said:

Just download the Anchor Alarm app to your cell phone. Works better, place the phone next to your pillow when you sleep so you can hear the alarm. Best part of all, you DONT need a cell signal for it to work, it’s working off of GPS, which works anywhere��

Click to expand...

What is the name of the app you use? I see 6 choices

We use Anchor Pro and are very happy. We tested it over several weeks during the day to check its reliability and found it to be very good.

We can sleep soundly at night with it running knowing that if we drag it will wake us up.

https://play.google.com/store/apps/details?id=com.webmajstr.anchorpro&hl=en_US

My Grandad made an app for an anchor alarm when I was a kid and it worked pretty well. It involved tying a fishing line to a bake bean can filled with concrete that was dropped beside the anchor on setting. The other end was fastened to a saucepan placed on the galley table under a large collection of pots and pans. If we ever dragged Grandma would jump up with such a start and a shot of adrenaline that she would have us re-set in no time. All the while the rest of us, including Grandad, slept like babies. I like JustBob’s idea of being able to recenter the circle, it makes total sense to me. Better even than Grandmas idea of where best to fasten the end of the fishing line to command Grandads full attention.

Bob

We too have been frustrated with plotter anchor alarm choices. Here is what we have done for a very long time.

This may be counterintuitive in the era of "electronics can solve everything" - use the right anchor and rode so dragging doesn't occur. Another tool we use is the depth alarm if really concerned, taking into account the specific anchorage and tide range.

Over the years we have found that using the plotter, with track on, to place a box around the well set anchor answers a lot of questions in the morning. The box should be large enough to compensate for wind and current variation during the tidal changes. Some use circles if available. We have dozens of saved boxes spotted around WA, BC and AK and return to them as first choices.

Opencpn.

Using mouse, right click > drop mark > set anchor alarm
Grab and drag into better spot if required

https://opencpn.org/wiki/dokuwiki/d...pn_user_manual:advanced_features:anchor_watch

When we're below, I can't always hear alarms from electronics on our bridge either, and those units take more power than a tablet or cell phone too, so we use tablet/phone apps closer to where we are.

A "survey" of anchor alarm apps:

http://www.trawlerforum.com/forums/s42/best-anchor-watch-alert-alarms-apps-41416.html

I think I did on one cruisersforum.com, too.

-Chris

The trouble is that a lot of software gets written by people who never use it. How many of the engineering at Garmin in Kansas do you thing are cruisers? Let along how many have anchored while trying to coordinate setting an alarm mark, let alone figure out how large a circle to set to allow for rode length, scope, and GPS position relative to bow, and over all boat length, let along been waken in the night by an alarm and a dragging anchor.


I haven't tried any of the phone apps because I fundamentally don't trust the phone reception and reliability when it's below deck. But I like the idea of one that uses the boats GPS over wifi. I could get comfortable with that.


So far the two I like, and I use them both together, are the anchor watch in Maretron's products, and the boundary circle in Coastal Explorer. I mark our position on both when the anchor touches down. Both have adjustable position and radius. And both can be wired to speakers that will wake the dead. CE tracks add some more info plotting boat movement and providing an excellent visual indicator of drag as you will see the boat's sweep slowly smearing down wind.


And in addition, I use a VNC (remote computer screen viewer/mirror) to let me watch the Maretron screen bedside on an iPad. My "At Anchor" Maretron screen have the anchor alarm which shows the swing circle and the boat's position and heading, plus weather info, and a bunch of other things I like to watch while at anchor. While sleeping, I can quickly glance over, see what's up, and if all is well, go right back to sleep without waking up too much.


It all works for me, and I have no doubt there are many, many equally good ways to accomplish the same thing.

Simi 60 said:

Opencpn.

Using mouse, right click > drop mark > set anchor alarm
Grab and drag into better spot if required

https://opencpn.org/wiki/dokuwiki/d...pn_user_manual:advanced_features:anchor_watch

Click to expand...

Right.... but I'm not using OpenCpn.

twistedtree said:

So far the two I like, and I use them both together, are the anchor watch in Maretron's products, and the boundary circle in Coastal Explorer. I mark our position on both when the anchor touches down. Both have adjustable position and radius. And both can be wired to speakers that will wake the dead. CE tracks add some more info plotting boat movement and providing an excellent visual indicator of drag as you will see the boat's sweep slowly smearing down wind.

Click to expand...

Thanks Twisted. Since I have both of these I shall give them a look!

OldDan1943 said:

JustBob, I have never figure out how big the circle should be. PLUS, the anchor alarm is of little good if it wont wake you while you are sleeping. I would think there should be a way to extend the anchor alarm to the stateroom or put a bell on the system so you can hear in in the stateroom.

Click to expand...

Was thinking about your question and (hard to believe) but college geometry reawakened in my brain and I recall that A squared + B squared = C squared.

If you are in 50 feet of water when you drop, that's A.

You pay out 150 of rode, that's B.

Do the math and that tells you that in theory your boat can only be 141 away from the anchor, max. Of course that will lengthen if the tide lowers, and shorten if the tide raises.

So I would say ignore the calculated value for b, and use how much rode you payed out. Add a fudge factor for some limited movement, tidal change, etc.

So for like this example I think a circle of 200' or 225' should work?

JustBob said:

Thanks Twisted. Since I have both of these I shall give them a look!

Click to expand...

One thing to watch out for with the Maretron anchor alarm that may not be obvious...... the alarm is only armed when the boat mode is set to “Anchored”. I found this out the hard way, but fortunately no grounding. They have subsequently placed a big “Armed” indicator on the anchor alarm to clearly show the status.

Bob
The circle really gets interesting to estimate in a 35' tidal range. In lighter airs our chain tends to move towards the anchor as currents shift and drag the chain every 6 hours. For these and other reasons we prefer a short scope, all chain and oversize anchor.

For our vessel, an anchor alarm powered from a depth sounder has proven much more meaningful than GPS sensing alone. Irregular bottoms - with that not charted high spot looming at low tide - has awoken us more than once.

If the master is far from the data center as is likely in your and TT's case, a Maretron or other unit parked near your bed can have all sorts of data alarmed in whether depth, position, genset status, inverter etc. In some large yachts I've seen a mini control room of data in the Captain's quarters.

JustBob said:

Was thinking about your question and (hard to believe) but college geometry reawakened in my brain and I recall that A squared + B squared = C squared.



If you are in 50 feet of water when you drop, that's A.



You pay out 150 of rode, that's B.



Do the math and that tells you that in theory your boat can only be 141 away from the anchor, max. Of course that will lengthen if the tide lowers, and shorten if the tide raises.



So I would say ignore the calculated value for b, and use how much rode you payed out. Add a fudge factor for some limited movement, tidal change, etc.



So for like this example I think a circle of 200' or 225' should work?

Click to expand...

Exactly, thought the ride length is C, but that’s not the point. The key is that ride length is a very close proxy for swing circle. But I also mentally add the boat length, plus a little for good measure. But with 150’ out, 225 seems like a good circle.

There are other subtleties that he-who-shall-not-be-named, formerly of ActiveCaptain argued because your GPS position is not the actual anchor drop point since your GPS is more midship and your anchor is at the bow. So in one direction that length difference adds to your circle, and in the opposite direction it subtracts. I think he was right about all that, but I also think that it really doesn’t matter unless you are trying to anchor within some small distance of other boats, and we all know that only sail boats do that

I'm still a fan of Anchor Pro on my Android phone. It uses GPS so doesn't need a cell signal. There is no problem maintaining a signal next to my bed. Just remember to set it when you drop the anchor and set the radius of the circle you want. I'm a light sleeper at anchor so I occasionally look over and see how far away from the anchor we are. It even has a nighttime setting so it is easier to see. And the alarm will wake up anyone.

sunchaser said:

Bob
For our vessel, an anchor alarm powered from a depth sounder has proven much more meaningful than GPS sensing alone. Irregular bottoms - with that not charted high spot looming at low tide - has awoken us more than once.

If the master is far from the data center as is likely in your and TT's case, a Maretron or other unit parked near your bed can have all sorts of data alarmed in whether depth, position, genset status, inverter etc. In some large yachts I've seen a mini control room of data in the Captain's quarters.

Click to expand...

First, I really like the idea of monitoring/alarming on the depth. I shall definitely play with this idea.

Second, I have the Garmin GMI-20 in the master stateroom so theoretically I can monitor anything in the Garmin system. I have heard about using it as anchor drag watch but don't know how to do it as of yet. It's a shame the Garmin manuals are so lacking in information.

twistedtree said:

Exactly, thought the ride length is C, but that’s not the point. The key is that ride length is a very close proxy for swing circle. But I also mentally add the boat length, plus a little for good measure. But with 150’ out, 225 seems like a good circle.

Click to expand...

Yes, I typo'd B when I should have said C. But you said "ride" and it's "rode," so brother we are even

Yes, kind of interesting about anchor placement vs where your GPS is. I think it is also likely that when you go to set the hook, you are going to drag it some distance before it digs in.

My Garmin system often reports that I'm WELL outside of the range I should be from my anchor (mark). Like 100 feet.

I got concerned that my chain counter wasn't accurate. That since Garmin is saying the boat is 225' away from the mark, that I really didn't let out 175', I payed out 200+.

So I carefully marked the chain and found that the chain counter is spot on.

So it seems to me the delta in my case could be a combination of the anchor platform vs GPS (which is probably 32-35 feet) and some dragging before the hook takes hold.

Probably if we need a level of precision inside of 50-75 feet we are in the wrong spot?

JustBob said:

Yes, I typo'd B when I should have said C. But you said "ride" and it's "rode," so brother we are even

Yes, kind of interesting about anchor placement vs where your GPS is. I think it is also likely that when you go to set the hook, you are going to drag it some distance before it digs in.

My Garmin system often reports that I'm WELL outside of the range I should be from my anchor (mark). Like 100 feet.

I got concerned that my chain counter wasn't accurate. That since Garmin is saying the boat is 225' away from the mark, that I really didn't let out 175', I payed out 200+.

So I carefully marked the chain and found that the chain counter is spot on.

So it seems to me the delta in my case could be a combination of the anchor platform vs GPS (which is probably 32-35 feet) and some dragging before the hook takes hold.

Probably if we need a level of precision inside of 50-75 feet we are in the wrong spot?

Click to expand...

"Ride", that's pretty funny. Totally missed it, but I'm good at missing typos, especially my own.


Another factor is GPS accuracy, and 9m is pretty common. So that adds another 30' of slop.


It's just not high accuracy stuff, so counting every detail isn't worth it.


That said, in shallow anchoring I can see how it starts to make more of a difference. Say 8' of water and 30' of chain. Your boat length and GPS error are 3x the rode length....

I was just playing with Anchor Pro on my I-phone and it seems that that GPS accuracy is stuck at 65 m . At that precision I'm "drifting" in and out of the allowed distance without moving.

What are other people who use Anchor Pro getting for GPS accuracy?

Actually, you can place the center anywhere you like. The process is:

Anchor drag alarm>edit alarm area>[touch center icon with arrows]>move center>[drag crosshairs to desired position]>set center>done.

I have an iPhone app called Drag Queen. I've never used it, except to ask others at a dinner party why I'd have an app called Drag Queen.

mikecurreri said:

Actually, you can place the center anywhere you like. The process is:

Anchor drag alarm>edit alarm area>[touch center icon with arrows]>move center>[drag crosshairs to desired position]>set center>done.

Click to expand...

Actually Mike is 100% correct! I'm on the boat now and just tried it. I admit I had several things going on when I tried this. I guess when I viewed the manual and this menu item wasn't even documented I quit to quickly.

[Looks a bit sheepish....]

But I also think it is pretty bogus that the Garmin tech I got connected with didn't even know this.

Now I'm going through the Audio Setup and will see about getting an audible alarm for the anchor drag.

Thanks Mike

boatguybill said:

I have an iPhone app called Drag Queen. I've never used it, except to ask others at a dinner party why I'd have an app called Drag Queen.

Click to expand...

It is supposed to be pretty good but, no longer available.
Maybe, they got a lot of negative comments from a certain segment and they renamed it. I do not know.

GPS drag alarm can alert if the anchor moves less than 10’ in any direction

Here are my two cents. I’ve thought about this anchor drag alarm problem a lot and think I have a solution. Please tell me what is wrong with the following if you disagree.

Get a gps locator that is powered by battery in a waterproof design. There are many variations on this used for tracking wayward dogs. You would want to get one that doesn’t require a monthly fee. They come with software that allows you to set it up any most anyway you desire. Then attach this gps monitor to a float that would keep it out of the water. Tie that float with a rope to the trip location on the anchor with a device in between that keeps the float directly or almost directly over the anchor. This could be a rope tied to an adjustable shock cord or an even more complicated device that maintains tension on the attachment rope to adjust for tides and currents to keep the float above the anchor. So instead of worrying about how to get the center of your circle now you only need to know the depth where your anchor settles to make any crude adjustments to your device to keep the float over your anchor.

This would sound an alarm when the anchor has dragged in any direction in as little as 10’. Gps are thought to be accurate at 5’ so current moving the float downstream should still generally alert by 10’.

So instead of having a huge circle that would not alert in all directions in less than the length of your scope plus, your anchor alarm would now be worth setting. And in today’s crowded anchorages a 50’ or even much larger alarm warning would be worthless. A wind shift with a traditional circle alarm might mean that the alarm would not go off with a scope of only 50’ unless you had dragged 50’ plus or more only even if you were able to pinpoint the exact center of that circle. If you weren’t able to pinpoint that center it could be far worse than that 50’. Of course a longer scope would make this problem even more dramatic.

Stephen

I know you want to make what you have work, but you could use this free one from Paul Lutus (smart guy up near you) who wrote Anchor Sentinel...
https://arachnoid.com/android/AnchorSentinel/index.html

Also, saw Vesper Watchmate 2 at Ft Lauderdale and it has built-in anchor watch and an alarm that will wake the dead...

https://www2.vespermarine.com/

Stubones99
Thanks for the information but since I have an Apple I don’t think this will work for me but more importantly any anchor watch which depends on the gps from a phone will not come close to achieving what this will do unless you position it on top of a float like in my suggested way! Most people wouldn’t want to place their phone on a float above their anchor! Then of course if you did that then you would need another phone or device on your boat to communicate with the phone above your anchor. The main reason my suggestion works so accurately is that the gps is located at the anchor not on the boat so when the anchor moves the phone on the boat is notified. Otherwise wind shifts would set off the alarms all night long.

I’m sorry but I haven’t been explaining this system very well. Hopefully this will clear up some of the confusion I created. My system doesn’t care where the boat is! A wind shift could move it 400’ or more and the alarm wouldn’t trigger if the anchor didn’t drag. Yet if the anchor only drags 5’-10’ the alarm would sound if you set it up to react quickly. So for those of you that anchor in fairly deep water this would be especially valuable.

Obviously the reason the float rope is attached to the anchor at the tripping spot is this would serve a dual purpose if your anchor snagged.