Garmin Aviation And Marine Devices Compatible With City Navigator North America NT

The MAPS 640 has both a marine and an automotive mode, and separate maps (I believe selectable) for each. So I can use the “auto” mode to get via highway to a launch ramp, then once on the water switch to the “marine” mode for on the water navigation.

It is interesting to me that Garmin seems to have done it with more aviation units than marine units.

I wonder if these are more accurate Garmin automobile navigators.

Following this topic with great interest for two reasons:

My early Garmin GPS units I purchased were marine/auto units as the they had better resolution/detail.

I am not particularly happy with automotive only Garmin GPS units that have come out after the Nuvi 3597.. one of the best units built per my experience and also comments of others in this forum.

The Nuvi 3597 is aging and would like a later generation unit but it needs to exceed to 3597's performance for me to be interested in purchasing.

I sent Garmin an email recently and was surprised that I received a reply yesterday on the Labor Day holiday.

This is what I sent:

"I am interested in getting the most accurate Garmin. I was looking at the various Garmin Aera models and the Garmin GPSMAP model, specifically the Aera 500, Aera 510, Aera 550, Aera 560, Aera 796 and the Garmin GPSMAP 640. All show that they are compatible with the City Navigator North America NT. Would they show more accurate GPS coordinates than the automobile navigators? https://www.garmin.com/en-US/p/1456#devices"

This is the reply that I received from Garmin.

"All of the aviation portables that you listed have been discontinued and are no longer for sale. The current aviation portables do not support street navigation.

If you are interested in a Garmin product that is used for street navigation, I would buy one dedicated to this task: https://www.garmin.com/en-US/c/automotive/car-gps-navigation...

Let me know if you have any questions.

Best Regards,

Brian
Garmin Aviation Support

For 24-hour access to support articles and videos, visit the Aviation Support Center."

Makes sense, cars don't fly and planes don't follow roads.

There is a certain appeal to the "Swiss Army Knife" concept for some things. For example, I have a Leatherman multi-tool. It works okay as pliers and okay as a screwdriver. However, some, perhaps many, all-in-one devices do many things poorly, rather than great.

For example, I owned both the Garminfone and the Garmin Nuvifone years ago. The idea was to use it as a phone, GPS navigator and for entertainment. My experience was that it did not do all of those things great.

On the other hand, many people do use their smartphone as a navigator and are quite happy with that, so "Your Mileage May Vary."

What is your goal here?

I'll use my circumstance with stereo equipment as an example. As an engineer I worked in acoustics for many years. I had both the knowledge and equipment to optimize a room to bring out the best in its acoustics. With some care in purchasing my stereo "gear" I ensured a great listening experience for myself and others. When friends visited, they commented on the listening experience. I was often asked to optimize their equipment. I was pleased with what I did, and others were pleased with what I did for them. Warm fuzzy feeling...

But I ask, what are you after with respect to "accuracy" on a GPS device?

I had a marine handheld (GPSMap 78?) that was supposed to work with City Navigator. It often crashed or was merely funkish. Garmin gave up on troubleshooting or figured it out and gave up on solving the problem. They gave me a Nuvi 40 or 50 (can't remember) as a decent consolation prize.

Increase my knowledge of how GPS works.

NASA has an extensive amount of material on how the GPS system works. I can tell you as a former Naval officer trained in navigation, that even after extensive training I would not profess to really know how it works. It is an amazingly complex system.

Now, this thread and your other thread (http://www.poi-factory.com/node/53280) seem to be looking at what you are terming "accuracy". In that other thread I stated that the use of the term "accuracy" as part of a GPS display is, IMO, a poor choice and I felt it would better be called potential accuracy. Having said that "potential accuracy" probably wouldn't fit on the display. But in any event that is what it is, potential. That stated accuracy (I think you linked to an image showing 17 feet) is at a moment in time. It is not an absolute. It is subject first of all to satellite positions relative to the horizon. If you have acquired, say early in the morning, six satellites, all relatively low on the horizon, that will yield a relatively low number as far as horizontal accuracy. But at noon, six satellites, even if they were the same satellites (extremely unlikely) would yield a higher number as far as horizontal accuracy. It would appear to be less accurate. There is also the vertical axis or displayed elevation to consider. A scattering of satellites low on the horizontal would not show as good an accuracy on elevation as would numerous satellites directly overhead. The typical diagram of satellites can be seen in a Garmin topic at https://support.garmin.com/en-US/?faq=CGLbyjTCVcAw055Oj9rHi5.... Thinking of that diagram as two concentric circles, the inner circle represents satellites that are 45° above the horizon; the outer "ring" represents satellites that are low in the sky, below 45°.

You'll note on the Garmin page I referenced that its says there is color coding to the various satellites that are shown; GPS (blue), Galileo (pink) and Glonass (green). In theory, and I don't know if it exists as an automotive device, the most accurate device under any given set of conditions, would be one that can acquire all three satellite systems and use that information within its internal algorithm. You'll note on that page that Galileo is not available on the Drive 53 series and the Glonass system is European only. So perhaps a high end device purchased in Europe that supports Galileo and Glonass would offer the best accuracy, at any given moment in time. I'm speculating that any such device even exists, and can utilize all the types of satellite data in determining position. Another issue is computing power; I believe there are 31 satellites in the GPS system, 24 in the Glonass system, and about 30 in the Galileo satellite system, once it becomes fully deployed. Do we need a device that can acquire almost 100 satellites and process that data? Only to improve that potential accuracy to the inch or centimeter level? What would be its cost, its size?

There are other satellite systems of note, some of which are maintained by their respective countries for military purposes. Two come to mind, QZSS (Japan) and BEIDOU (China). There is also the differential system which in theory the most accurate. It is also called GRASS GRound Augmentation for Satellite Systems (also called Wide-Area DGPS or WADGPS). The differential system can yield accuracies down to about an inch. See the topic at https://en.wikipedia.org/wiki/Differential_GPS. Note that differential systems are being investigated and prototypes are being used in the automotive area for self-driving systems. Some of these systems can avoid curbs by inches when the vehicle makes a hard right turn in self-driving mode. A few weeks ago however a Tesla suffered major damage while being in self-drive mode; the system took the car through very deep water at high speed. More work needed, but not necessarily on the navigation system!

I'll end by saying, as I started, it is an amazingly complex system.

That the military has a system that is capable of what you are seeking, but you will never be able to attain one. First, the cost would be prohibitive and secondly, the answer that they would give us, you don’t need it and if you don’t need it, you can’t have it.

My GPSMAP 64ST receives Glonass in North America. I thought it did in South America but my memory is uncertain.

Just in case,,, I wish I knew how to turn Glonass off.

Anything like the content at link below of help?

https://www8.garmin.com/manuals-apac/webhelp/venusq/EN-SG/GU...

Thank you!! It is in the "64" manual too.