T&T: Anchoring and anchor watch

[Jeffrey Siegel]

> Until he can do that I will get up when it swings. Go for it Jeff.
> 

It can wake you up when you swing or when the wind is above a certain
threshold too.  It's something that I'm playing with on this trip to the
Bahamas.  Here's what I did:

I had been using the ShipModul MiniPlex-41BT
(http://www.shipmodul.com/en/index.html) to move data to and from my mobile
devices and the Raymarine system.  I was also using the 41BT to repeat the
Raystar GPS over Bluetooth instead of having to have a separate Bluetooth
GPS.  It all worked great.

Then I was working on the anchor software and couldn't understand why the
phone was receiving so many NMEA sentences.  When I dumped them I realized
that ALL of the Raymarine data was being converted to NMEA and broadcast
over Bluetooth.  Since I leave all of the electronics on while anchoring (to
use Raymarine's anchor alarm, depth, etc) all of that data was available at
the phone.  I immediately tied the rotation of the GPS cursor to the heading
sentence instead of the COG parameter.  Voila...the cursor swung around and
now shows the orientation, not the direction of travel.

Since I have wind and depth sensors, that data is also available on the
phone.  If I can see the data, I can make the phone make a lot of noise when
it crosses some threshold.  If you want to be woken up when the wind reaches
25 kts, it'll do it.


> How does a cell phone function as an anchor alarm?   I assume we're
> talking a phone with GPS capability, but how do you use it as an
> anchoring alarm?

I actually don't own a device with a built-in GPS.  I'm using an external
GPS - either the Raymarine as described above or a separate Bluetooth GPS.
Having an external GPS is better for this application because you can leave
the GPS at the helm with a good view of the sky while you're tucked away in
bed with the phone next to you.

The software I'm working on for this should work on medium-to-high-end
phones.  My lowest-end type of phone that I'm testing with is a Motorola
Razr which often costs about $19 today with a plan.  I wouldn't suggest that
phone for most cruising use because it doesn't do email and the web browsing
on it is pretty bad.  There are better choices.  The thing is that there are
so many of those Razr's out there...


> I'd rather leave a cell phone on all night on its own battery
> than run our big plotters on the boat's batteries all night.

I'm using a little Audiovox SMT-5600 for real anchoring use now.
www.activemap.com has a picture of what it looks like with a nautical chart
on it.  That device holds a charge for about 20 hours while connected to the
GPS and monitoring the position every 2 seconds.  It turns its screen off
unless you press a button.  I often wake up, tap the up button, and it shows
me right where I am with the proper orientation and the position of my
anchor.  I honestly sleep much better with it!

==================================
Jeffrey Siegel
M/V aCappella
DeFever 53PH
W1ACA/WDB4350
Castine, Maine

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Cruising blog to Abacos & Maine:
http://mvacappella.blogspot.com