Bad weather (and satellite reception)

Yes.

Oh, you want to know what that reason is too, don't you?

Well, water can adsorb and thus block radio waves. That's one of the reasons that submarines can't use the same type of radio signals that other ships use, or have to float an antenna to use them, or that they use sonar rather than radar. Well, rain can block those signals (a phenomena called "rain-fade"). Snow, being water can also cause this. You can even have rain-fade when it isn't raining or snowing on the ground, as sometimes it is "raining in the clouds" but that rain never reaches the ground.

You will also find that you have problems getting a signal under dense foliage (due partly to water in the leaves), and this problem is increased if it has rained and the leaves are wet).

You'll also experience rain-fade with direct broadcast TV signals, particularly if you have a small dish (the larger dishes are also subject to it, but since they have better "gain" they are less likely to have reception loss due to it).

I have been wondering about that the last couple days too....my 765T seems less responsive at times, then fine later on...but maybe it is just my imagination

Both my 350 and 760 have worked fine during VERY heavy snowstorms here. Checking the satellite screen showed that the accuracy was down from the typical 12 feet to 17 feet or so during the heaviest storms. No complaints or concerns during heavy storms at all.

GPS receivers are really pretty amazing -- using correlation techniques they can dig out signals that are really, really weak.

One of the side-effects of this is that you can get away with some pretty cheezy antennas if you make the bet that you're going to have clear sky most of the time.

As pointed out, a lot of water vapor (such as snow, heavy rain, dense foliage) attenuates the signal a great deal.

That's where a good externally mounted antenna, one with a built-in low noise preamp, and a short cable with a good connector can work wonders! An older Garmin (GPS 45) I have has a helical antenna. During rainstorms, it can't "see" much of anything. But when I connect it to my external (Trimble) antenna on the roof, it can see plenty of birds!

GPS is used for mission critical work. It's not like satellite TV, where a rain fade out now and then is only an inconvenience.

Rain and snow do attenuate the signals to some degree, but not enough to stop a GPS unit from working. You'd need some pretty sensitive test equipment to actually measure the loss.

When the engineers designed the global positioning satellite system, they realized that it might have to be used in heavy rain and snow. They designed the system to work under these conditions.

I suspect that some of signal loss people report is being caused by windshield wipers flopping back and forth, or perhaps radio static created by the vehicle's blower fan motor.

The S in GPS stands for System. The system includes the receiver. A small car receiver with an internal antenna isn't designed for mission critical work. Any such system that considered itself critical should have a much better antenna, which would greatly reduce the problem

No, other posters here (as well as my own observations) indicate that you can see the loss quite well with a "GPS unit", as long as that unit is limited by an internal antenna or other signal limited antenna.

They didn't design the Garmin receiver, which when used to navigate a car becomes part of that "system". Garmin took reasonable design approaches for them, but that does boil down to cut corners that can impact performance in precipitation conditions.

Yea, there are likely a lot of factors that contribute to signal loss. Coated windshields (and even the normal glass windshield itself) may contribute a lot more than wipers, but I can't rule wipers out. Same for a blower, although ignition sparks are a much more likely contributor of signal noise. Yet the Garmin is designed to work inside a car, so it's curious that you would think the engineers who designed the system could protect us from rain fade but would ignore common issues known to exist where the unit is intended to be used.

Overall there are a lot of factors that contribute to signal loss, including the metal roof of the car blocking a line of site view to some satellites. With a tiny internal antenna it's a wonder it works at all. but rain-fade is certainly an issue that can affect such reception.

Let's just leave it at that.

Mine has worked fine so far in all weather conditions.

but have you noticed that occasionally under those weather conditons, that the vehicle is not exactly on the route or street that you are on?

mine is still functioning, still acquiring a signal, and still navigates, but sometimes the map shows me just slightly off the road.

no big deal, just an observation.

Ugh, imagine being on an unfamiliar highway in one of those snowstorms with enough snow to cover the signs so you can't tell where your exit is, and thinking, well, at least I've got my GPS to get me where I'm going, and then lose that signal because of the weather. That would really be scary.

I've been very fortunate to have not suffered signal loss on either GPS or satellite radio due to rain fade or other weather issues. Coated glass, yes, but weather, no. I've never had satellite TV but I do hear people complain about not being able to get their signal because of rain/snow fade or snow buildup on the dish.

Worse for me, my GPS (Nuvi 200) was off by almost a mile when the weather turned bad 2 weeks ago. It was shown that I was driving on the river.

Jef

Never had a problem due to weather, and I've driven in some really nasty storms. Last August I was heading up to Idaho and got caught in a thunderstorm so bad that we literally couldn't see through the windshield even with the wipers going full blast... it was like sitting under a waterfall. I had to pull over and wait for it to subside... but My Nuvi 260 never missed a beat.

maybe the bad wether blew the gps in the sky out of alignment =P

mine works fine as well, it just takes a little longer to link up.

Before my Garmin Nuvi 205w I used the FineDigital 400, a lot more features than the nuvi, but only occacional map updates and no means to build and load custom POI's except when using the unit manually. However, in any cloudy conditions the satellite reception takes forever to acquire, but with the Nuvi 205w I have had no problems at all attaining the satellites and even in a heavy rain storm the satellites were acquired before I was ready to navigate.

I just went through that Midwest ice storm a few days ago and GPS worked great even with ice on all but the windshield

No reception problems traveling from Minnesota to AZ during the winter. Basically, through snow/ice (-40F winter) and desert heat (+120F summer), my 660 never lost satellite connections. Depending on the hotel, I still got reception indoors if not too far from a window (handy when looking for food locations before actually leaving the hotel).

Also, did a road trip from AZ to FL and got touched by Hurricane Gustav and didn't lose Satellite connection.

Surprisingly, when driving in downtown San Francisco, between the high-rises and up/down the hills, I didn't loose Satellite connection either.

To summarize, my 660's reception has not failed me in snow, ice, desert heat, hurricane wind/rain, and sky scrapers.

As others have noted, the windshield suction doesn't do well in the extreme cold/heat conditions I go through, so I use the Garmin bean-bag. It doesn't leave the "suction" ring on the window for "would-be-thieves" is an added bonus.

Hope this helps...

Yes, the Garmin bean-bag, as has been endorsed in numerous other threads, is highly recommended over windshield suction mounts for these reasons.

Garmin also make many units for aircraft including GPSMAP 196 portable. I don't think I need to say any more with the exception that I know that certain things in your car can effect signal strength. My XM radio is my largest problem when I'm receiving a week signal because of terrain I turn off my XM and the signal will be strong.

I've taken my 350 through New England weather, snow, rain, ice, everything. It has not dropped satellite even once, nor lost any appreciable accuracy. It's great, it tell me to turn when I can't even see the street sign. Or the street itself. Really.

I run into the parallel road-lock problem more than anything.