GPS / snow ?

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**** I'm about to go to Ketchikan and the forcast is snow and rain showers. So far I havent been in snow, underway with rthe boat. My TV antenna dies at the house*with considerable wet snow and I would expect the GPS with it's small antenna to not work as well. Without GPS I'll probably go for the radar but the same would seem to apply to that as well. With no GPS and no radar I'll be with my compass, last known position and depth sounders. Also if the snow is heavy I won't see squat.

Eric Henning

Eric, I have never heard of snow "attenuating" a GPS signal. I have no clue what frequency range the GPS signal is broadcast in but I would think that would one of the places to start. Also, your TV signal is one transmitter and one reciever. The GPS system has many satellites and you only need a few for proper operation. I am just shooting in the dark here. My uneducated guess would be that snow would not be a threat to the GPS signal.

Here is the first link in my google search:

http://gpsinformation.net/gpsclouds.htm

I would suggest going to google and do:*** google+snow****

You may get a tighter search if you put it in quotes.* But I think there is tons of info there...TONS!!!

Whoops.....I just saw my mistake.* I meant,*** GPS+SNOW** !!!!

-- Edited by Baker at 10:02, 2009-01-27

Eric, Neither rain nor snow nor dark of night should affect your GPS and if anything does it is an antenna issue and not conditions. Have fun

Hi guys,

Thanks for the uplifting thoughts on snow/GPS. I leave at O dark thirty in the morning for Ketchikan and snow is prominent in the forecast. I riged a life line ( fixed ) to make it easier to wipe the snow off the little mushroom guy up on the radar arch if nessessary when it's rough. Welcome to the site Chuck. Looks like you've got stuff to share .. good. We've got lots of fiction and fact to sling around here.

Eric Henning

Eric---

We've had our boat out in heavy rain and while it certainly affected the radar returns it had no effect whatsoever on the GPS. We never run our boat from the flying bridge so the heavy canvas cover stays on all the time when we're running. The two GPS antennas are mounted on the flying bridge consol underneath this cover, but they never miss a beat, even under the cover AND in heavy rain. I've also driven a car in France in heavy rain and mixed snow at 60-plus mph and this had no effect whatsoever on the GPS nav system in the car. So I will be very surprised if you experience any interuption or inaccuracy of your GPS system in the snow and rain you may encounter. Have a good trip.

GPS frequency is 1.5 and 1.2 GHz, so its shortest wavelength is about .2 meters, or about 8 inches.

Radio signals peneterate water to about 1/8 of the wavelength, or about an inch at 1.5 GHz.* Not many raindrops are that big!* Not to say that an extremely heavy downpour won't cause some attenuation, but in general, you'll never see it with a good antenna and coax.

Radar is up at about 10 GHz - now your wavelength is under an inch, and 1/8 wavelength around a tenth of an inch.* A good heavy rain now becomes significant.