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Old 01-12-2013, 06:53   #61
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Re: AIS Application for ipad?

BTW . . . I don't think anyone has mentioned it yet . . . but there is a new AIS protocol called 'class E' specifically designed for smart phones and ipads on recreational boats.

It's development is being funded by the US Department of homeland security. It is interesting to know that their explicit objective is to get more recreational boaters (voluntarily) using it, so that they can be more easily tracked for law enforcement purposes.

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Old 01-12-2013, 09:23   #62
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Re: AIS Application for ipad?

Originally Posted by Buzzman View Post
Yeah, okay - a "technical" hijack - it's a related question and as the second post on the thread asked "how are you receiving AIS"? I figured it was relevant.

So the "AIS Apps" use land-based clients that can have delays and so can't be relied upon for nav purposes....I get that....

But the word "application" as used by the OP does *not* necessarily exclude other means of receiving AIS info than simply "iPad Apps" from iTunes.

And receiving AIS from either a dedicated receiver, or a VHF radio with AIS functionality, are certainly "applications" that could be utilised to enable AIS overlays on an iPad 'chartplotter'.

OK, so the OP did not ask "how can I get AIS onto my iPad", but that is the question I'm 'assuming' was asked. Shoot me.

Hence my query as to why there is a need to have effectively two GPS units. You're paying for both of them, so if one is redundant, that's a *waste* of money, isn't it?

From what I've been told by those in the know (offline) the iPads GPS would need EITHER functionality added to a chartplotter app (to send its GPS data wirelesly to the AIS/VHF radio), or a dedicated "feed GPS data via wifi to external device" app, which it appears no-one has so far developed.

What I'm trying to get at is that 'dedicated brand name' AIS units - whether receiver only or Class b transponders, seem horrendously expensive, compared to Nav apps. $50 for a chartplotter app; $200 for a dedicated AIS receiver, $1000+ for a Class b transponder.

What I was looking at was based on someone needing to buy both iPad and VHF radio *and* wanting AIS functionality, and finding the cheapest workable solution.

Ideally Class b, but in its absence, receive-only - hence why looking at the SH 2120 (for example).

Essentially, purchasing a 2120 adds about $100 to the cost of similar good quality VHF-only radio, which appears to be cheaper than the cost of a low-end VHF radio plus a dedicated AIS-receiver (like an EM Trek B100 or AMEC CYPHO). And the low end VHF would likely not have DSC functionality, so this is an added bonus.

So apparently cheaper than dedicated VHF plus dedicated AIS receiver.

But as others have acknowledged, the 2120 needs a GPS signal to show 'ownship' and thus the relevant local area shipping (and to assist the DSC function).

So would a hockey puck GPS + wifi-only iPad do the same job as the GPS-enabled iPad - and could this also be cheaper...??

Supplementary question: does anyone know if its posible for the GPS data form the iPad to be used by either a dedicated AIS receiver OR a VHF/AIS/DSC radio? Is my oinformant correct and this is currently "not possible" until someone invents/writes a sepcific "app" for the iPad to enable it?

So in the meantime, a SH 2120 (for example), plus puck GPS, plus wifi-only iPad, would be cheaper than "dedicated VHF plus dedicated AIS receiver plus GPS-enabled iPad"...

And if so, then you'd only need a very simple NMEA to wifi 'bridge' (or router) to carry the merged AIS/GPS data to the iPad, with no need for the 'bridge' or 'multiplexer' to have a GPS function.

So this ought to be cheaper than than using a dedicated 'wifi bridge with GPS' such as the DMK Box 11A GPS at $500.

So my question basically is this - would this cheaper option require a separate "AIS app" as per the OP, or could the "chartplotter app" take it direct (eg: iNavX or Navionics for example?)

And further supplementary: why does a 'receive only' AIS unit start from $200, while Class b tronsponders start fom $900.

Am I missing something here? Why is AIS so expensive?
I've reread this thread a couple times looking for options for an inexpensive AIS transponder. I think you summarized the options very well. A couple of things that haven't been mentioned,

There are a number of inexpensive RS232 Serial to Wifi devices, with prices starting around $50. I bought an inexpensive Chinese box off of eBay, built a RS232 serial cable attached to my Raymarine RS232/Seatalk Interface box.

One key consideration is to make sure the input voltage can handle the boat's voltage range. I wired direct to the 12vdc, with the expectation that the box can handle 10-14 volts.

I had to make a serial cable. This is essentially DB9 connector with send and ground pins 2 & 5 connected to the Raymarine NMEA 0183 out.

Configuring the wifi box was a challenge. First there's the serial configuration (N-8-1 4800 baud), and then the "adhoc" networking, with a fixed IP address. Most importantly, with this being an inexpensive Chinese box, there was minimal documentation and what was provided was in Chinese, and the configuration tools weren't very usable. I don't look forward to changing the configuration.

If/when your iPhone/iPad is connected to the adhoc network, the phone/tablet is expecting all network traffic to come through the boat's wifi network. What this means is you won't be receiving any internet data over cellular network - e.g., email, web based AIS. I've been surprised by this several times (wondering why no data on mAIS or BoatBeacon)!

This gives me all the boats NMEA 0183 data on my iPad. I've found iNavX and iRegatta to display the NMEA 0183 data on the iPad.

The other thing is that the AIS data is 38400 baud, while the NMEA 0183 is 4800 baud. You can't expect the two data transfer speeds to combine without some sort of multiplexing device.

It has been said a number of times on this forum, it is difficult to read the iPad screen in full-sunlight.

This was an interesting experiment. For us, the iPad is NOT an essential navigation instrument. I've been using it to help with our performance sailing and tracking our boat polar speeds, etc. When I look at adding AIS to this configuration, I get a little worried about all this working well together. It would have been a lot easier to use one of the fit-for-purpose marine NMEA/wifi devices.


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Old 01-12-2013, 10:30   #63
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Re: AIS Application for ipad?

Originally Posted by Buzzman View Post
Basically I've concluded that the "lowest cost" option to get a chartplotter on my boat is a 'wifi-only' iPad running iNavX with an external hockey-puck GPS which could also feed GPS data to an AIS receiver/transponder and/or a DSC-equipped VHF radio.

So, essentially, all I would need is a 'multiplexer' that can accept NMEA data from other instruments (such as wind and depth) and from the AIS device (which I believe needs a port capable of running 38400 baud, rather than the standard NMEA 0183/200 4800 baud rate), and send that data over wifi to the iPad.

So something like the DMK Box 11A (GPS), or the Madman Marine 'bridge' (which the developer assures me can be configured for 38400 baud 'on request').
Does that make sense, or is there a better, lower cost solution?
A complete setup using a low-cost computer (raspberry pi is <AUD40 and still under 100 once you've added in gubbins like a case, power supply and sd card) and free software will be half that of your DMK box and far more expandable. Easiest option is to use it in conjunction with a cheap wifi router, but with more work you can make it into an access point itself. If you buy one of the boxes you're suggesting and later add in some kind of long rage wifi device to pick up wireless on shore, you'll have to disconnect from one network and connect to the other if you want to flip between browsing the web and seeing your position. With the homebrew approach everything's on one network.

How robust is the homebrew approach? not industrial strength (on the hardware front), but I don't note "nmea certified" on the boxes you're suggesting, there's no mention that the ports are opto-isolated and the ipad is hardly mission-critical ruggedized hardware. I wouldn't run the gps only through the computer/multiplexer, I'd have 2 listeners: one the DSC radio (a direct connection) and the other the multiplexer. Or just have 2 GPS receivers: The globalsat ones are cheap (~AUD50 inc postage?) and if you buy a serial one for the radio, you'd save yourself the cost of a serial to usb connector by buying the second GPS receiver with a usb interface. Redundancy is always good (except the type where they tell you your job's been outsourced to a lower cost location).

Do you need to be an ubergeek to do the homebrew thing? No. No programming involved. Some basic logging onto a computer and setting up a simple configuration file but nothing a reasonably clever 12 year old couldn't do. Reasonably clever 12 year olds generally give good rates on doing computer installations for you too.

Here's some notes I put together for a friend on doing this. Done in a bit of a hurry so may not be perfect:
Pi NMEA multiplexer
Another member of this forum installed the multiplexing software directly onto a wireless router running an open source OS:
Springy Tech..: August 2013

There are plenty of other homebrew ways of doing this. Using a laptop running opencpn as a bridge between NMEA and your ipad would work. Another contributor to the forum has posted here about his project which uses a pi and an arduino board which might be worth a look as another alternative:
Freeboard [MeshCMS]

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ais, Ipad

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