CONTINUOUSWAVE

I'm still investigating a 1990 Boston Whaler 31 for purchase. viewtopic.php?f=9&t=223

The boat does not have a GPS, but old 1990 Furuno electronics (1830 radar, fathometer, CB radio(!)). A stand alone GPS wold be great and from the link above, it looks like I could connect radar, fatho, etc. to it. I could get a used one for $500 and a new fancy unit for many thousands. Easy to mount in the overhead electronics box, but limited in screen size.

But talking to some folks around here, they're saying get a laptop with a much bigger screen and run the chart software from that. Several drawbacks to the laptop, won't fit in the electronics box and must be secured to the dash somewhere, needs a mouse(?), not marinized.

How does a laptop computer use a 12 volt system on a boat?

Thanks in advance.

JimP

For most laptop computers there is usually a battery charger available that will run from 12-Volts DC. When I was working in corporate computing, I used to always buy these 12-Volt computer power supply-charger units from LIND ELECTRONICS in Minnesota. They made good stuff, and had excellent warranty and service. As you can imagine, a "company laptop" that rides around in a truck or van is subject to a lot of abuse. The on-the-road users took quite a toll on laptops and battery chargers. The LIND products were generally able to stand up--although nothing could survive forever in that environment.

As an laptop owner and user, I am sure you'd take a lot better care of the 12-Volt DC power supply-charger unit. Look at the LIND company products. See the "auto adaptor" page of their website, at

http://lindelectronics.com/auto-adapters/

You will find they are used in a lot of rugged service situations, like police, military, ambulance, and so on.

Lately the battery voltage in laptops seems to be higher than 12-Volts, so the 12-Volt chargers are really DC-to-DC voltage convertors that step up 12-Volts to more like 20-Volts. (The exact voltage depends on the laptop and what battery it uses.)

The only problem with LIND--and most other after-market suppliers--is they don't have a 12-Volt supply for an Apple laptop. I think Apple's patented and proprietary mag-lock connector is the stumbling block. For an Apple laptop you'd have to look for a specialty product. Something like this:

http://www.amazon.com/Cybertech-MagSafe-Charger-Adapter-Notebook/dp/B006RAF0NY

The older models of the Apple Mac-mini were once popular for boats because they had an external AC power brick and you could easily adapt them to run on DC by just substituting the appropriate DC-to-DC convertor instead of the AC brick. But the newer models put the AC-power supply inside the case, and it is hard to get in there to hack around and make it run on DC. The attraction of the Mac-mini was its teeny-tiny power consumption. It only ran about 7-Watts of power, so it was popular for cruising sailboaters who needed to conserve battery power.

The big problems with a computer on a small boat are:

--the display brightness; you need a specialty display that is really high brightness to be able to see it in direct sunlight; most laptops won't cut it with their own displays

--you need something really water proof, as it is only a matter of time before it gets wet on a boat at the helm.

I have looked at using an Apple Mac-mini or similar HP micro computer on the boat, but the high cost of the marine high-brightness, water-proof, touchscreen display is always a deal breaker. Those displays cost $1,500 or more.

JimH -

Happy New Year and thanks for the info.

Hadn't thought of the Mac's. My daughter has an old 2003 Powerbook with 12" screen she used in college. Might be too old for the newer charting software(?). Wonder if I could use that? I'll have to look at it tonight.

Excellent points on brightness (hadn't thought of that) and waterproof. Seems you always have wet hands, spray, or moisture on a boat. I looked at some pictures I took of the boat when I flew over to Sitka in December, she has a cigarette lighter plug. I still need to find a convenient flat spot to secure a laptop.

Seems to be getting more complicated. Try to do it on a budget and the costs seem to rise. Have to keep the costs down because if I don't my wife gets a new car. Not sure how that works!

Simplest still might be to get used 10" chartplotter and antenna off of eBay.

Funny story, back in my Coast Guard days of buoy tending we serviced the floating aids on the Alaska Peninsula. We had just received some ruggedized laptops in 1991/1992 to use for positioning and we could send the laptops out in a "waterproof" box to position aids with the smallboat. Except the laptop batteries died rapidly when they got cold (below freezing). So we added a lightbulb to the container for heat. Kept the laptops going longer.

Thanks again.

JimP

Having an iPad Mini reduced most of the angst trying to decide on a backup to the existing chart plotter. I bought a waterproof touch screen rubberized case and a subscription to Marine US. Could not be easier.

Regards - Don

Don--how do your power the Apple iPad Mini tablet?

Using an Apple iPad for navigation is a very viable option. We cruised for a few days with Don J aboard his 40-footer, and relied mainly on an Apple iPad for navigation at the flybridge helm station.

If considering an Apple iPad, to get a GNSS receiver internal to the iPad you have to buy one with a Wireless or Cellular Data option. This usually adds about $120 or more to the price of the iPad. An alternative to getting the GNSS receiver in the iPad is to use an external GNSS receiver with Bluetooth connectivity. For example:

Dual SkyPro XGPS160
Universal Bluetooth® GPS receiver for portable devices
http://www.crutchfield.com/p_070XGPS160 ... tml?tp=148

This external GNSS receiver is $150. It can connect to several devices simultaneously. It also offers data logging features. It is WAAS capable, and also receives GLONASS in addition to GPS. Of course, you have to keep its battery charged, although a 10-hour battery life is claimed. This could be a bit tedious on a long cruise. But if you can manage the battery charging to a second device, it could be an interesting option. You could locate the external GNSS receiver is a prime spot for best view of the sky.

A similar $100 model omits the data recording, only pairs with one device, and only has 8.5-hour battery life.

[I power] the Apple iPad Mini with a cigar lighter plug, borrowed from the tow vehicle. With the mini, I bought the cellular data option that included the GPS receiver.

JimP--the above may be a bit confusing. In order for the Marine US app to work, you don't need to sign up for any cellular data plan, you just need the [cellular data modem] chip that is [provided in the Apple iPad Mini with] the cellular data "guts."

The newer iPad and iPad Mini may now have the GNSS receiver as standard. I don't know.

Regards - Don

As far as I can tell, Apple iPad models that do not have a cellular data modem do not have a GNSS receiver in them. There is a bit of a symbiotic relationship between them.

There is a very distinct advantage in GNSS technology to have a cellular data modem and a GNSS receiver working together for receiving GPS satellites. There is a mode called "Assisted GPS" or A-GPS. A GNSS receiver that supports A-GPS mode and has a cellular data link to a cellular provider that also supports A-GPS will be able to have an almost instantaneously fast time to first position fix. I won't go into the details of how this works, but it works extremely well.

There is a great deal of confusion about how mobile devices determine their position. One often hears comments about position determination using "triangulation" among cell towers. This is not at all what A-GPS does. A-GPS determines position from satellite pseudo-range solutions. The GPS process is "assisted" by the cellular data modem connection. The cellular data modem can deliver important navigation message data at very high speeds. Without this assistance, a GPS receiver may take as long as 15 to 30-minutes to receive all of that data from the satellites themselves because the rate of data transmission is very, very slow.

Getting back to the iPad, if there is no cellular data modem, an internal GNSS receiver would not be able to get the very fast position solutions that could be had with A-GPS technology. Of course, if you are 40-miles offshore and not in range of any cellular data network, the GNSS receiver in an iPad won't be operating with A-GPS.

Once a GPS receiver gets the whole navigation message, either via cellular with A-GPS or from the satellites themselves, the message content is not rapidly changing. This means that once you get the whole message and get good satellite lock, you don't get much futher assistance from A-GPS. The principal advantage of A-GPS is to allow mobile devices to get a very rapid position solution. Since mobile devices are often in difficult receiving environments for satellite reception, A-GPS can be a very significant enhancement. In the middle of a lake with an unobstructed clear view of the sky, A-GPS is not as crucial.

If you do buy an iPad with a cellular data modem and GNSS receiver, and you do not have an active data plan, I doubt you will get A-GPS help. I am not positive about that, but I would be surprised that a cellular data network would let a cellular data device connect and get any data from its network unless it was a subscriber. But perhaps they make an exception for A-GPS. I'd have to investigate that. The iPad, once out of range of a cellular data network, with or without a subscription plan, is not going to get an A-GPS help from the cellular network. Its GPS receiver will be running in autonomous mode.

ASIDE: I can understand the confusion about cellular telephone network and how they assist a GPS receiver. I really had no idea myself how A-GPS worked until about a year ago. I took a university-level course in GNSS technology at Stanford University via a MOOC (or massively open online course). One of the instructors was an expert in A-GPS who developed many of the methods and holds many of the patents. The course covered A-GPS in some detail. It was a very intensive ten-week course and I devoted about 100-hours of study to complete it. It was enormously informative.

A dedicated marine computer like the just released Digital Yacht AQUA COMPACT PRO should also be considered.

Wow. You guys are 10-years ahead of me (or more). I use a basic Tracfone and love it. My wife and daughters mutter comments under their breath.

Maybe I'm leaning towards the simple marine GPS chartplotter.

Jim -

I didn't notice any appreciable lag when using the iPad Mini and the Marine US application. And I never activated any cellular data plan for the 'pad.

Regards - Don

Don--I'm not familiar with the Marine US application. What is it? Thanks--JimP