Author Topic: this may be dumb but (Read 777 times)

rickyp · « **on:** January 25, 2006, 03:03:10 AM »

Will heavy clouds, rain , falling snow, or fog affect a GPS unit?

Graybeard · « **Reply #1 on:** January 25, 2006, 03:07:08 AM »

Doesn't affect my Garmin that I can tell and neither does a heavy tree canopy.

victorcharlie · « **Reply #2 on:** January 25, 2006, 06:51:04 AM »

Yes. Rain, snow, and heavy clouds can, and does affect most GPS units, and rain fade can occur, just like it does on sat. TV. Some times it just affects the accuracy, but can have a total loss of signal..... Tall buildings in a downtown area can cause a loss of signal as well.

I will on occasion, get a loss of sat signal, and the unit will go searching for signal. The signals are usually found again if I walk a few feet........

This time of year, with the leaves gone from the trees, I don't have much of a problem even on rainy days.......but it can happen.

Siskiyou · « **Reply #3 on:** January 25, 2006, 09:27:29 AM »

I have not had a real problem in stormy weather. But I will do a little bit of testing. I have basic information I have been posting regarding satellite tracking at different times. Victorcharlie has contributed to that topic. We have a small storm coming in later this week. I will try and setup my two handheld gps units and see what the results are.

I expect there will not be a major difference. Remember the WAAS system has been setup for aircraft navigation by the FAA. If the system failed during stormy weather it would not be suitable for aircraft. The FAA has certified a number of gps guidence systems for aircraft. Two of the biggest are the Garmin 530 and 430. Daveinwv as a C130 guy may know more about this.

My old mind flashed back to this last deer season. I was out in the woods in my wool getting rained and snowed on. I had my gps in tracking mode all day. Visibility was limited, and at times I was in tall timber. When I printed my track map there had been no loss of signal. I believe a bigger impact is satellite coverage for an area at a given time. While the DOD will no longer degrade the signal it can still move satelittes around to provide better coverage in areas that DOD needs it. As I have posted before license surveyors now print out satellite coverage for an area the are working. They take advantage of this data to time their work in the field.

The ultimate test would be a sandstorm in Iraq, or lacking that a afternoon sandstorm at Canyon Lands airport in Utah.

Siskiyou · « **Reply #4 on:** January 28, 2006, 04:08:55 PM »

100% cloud cover today with a good rain this afternoon and evening. I was out with my Garmin 76C today. No problem with satellites. At my best location with the amplified antenna off I was recieving seven satellites inside the cab of my pickup. When I plugged in the amplifed antenna I recieved eleven satellites. This with the antenna attached to a side window of the extended cab. Not an ideal location. I would not be surprised to have received a 12th satellite if the antenna was located outside on the center of the roof. Taking advantage of no obstruction and a good ground plane.

I have also been using the eTrex Legend on a window seal during cloudy, and rainy weather. Reception seems to be normal.

victorcharlie · « **Reply #5 on:** January 28, 2006, 06:30:41 PM »

Drove 3 hours to Middle Tennessee to rabbit hunt today......and had the GPS on all day.......almost every time I took it out of my vest pocket it said unable to locate need clear view of the sky. If I hold it in my hand this never happens........I wouldn't think the medium weight fabric in an orange shell and game vest would defeat more RF than say a metal truck cab.......These are real world conditions, where I'm moving in and out of very thick briar brambles, as well as into and out of very narrow valleys between steep, almost straight up hills.....under these conditions, when I download the track log to map source, I will have some gaps where I just don't get a signal.......Again, if I hold the GPS out in the open in my hand then it works great. It's difficult to hold the unit while carrying a shotgun and pushing through the brambles behind the dogs......This is tough hunting and it takes all I can do to just fight through the brambles..........

We did kill a few rabbits though! My poor dogs are sure out of shape......they were ready to get back in the truck after about 4 hours of this......but, so was I......

Siskiyou · « **Reply #6 on:** January 29, 2006, 06:11:36 AM »

victorcharlie: Sounds like you were on a tough piece of dirt. The topographic conditions you discribe have caused me some problems at times with the gps. When I am down in a canyon, I lose the horizon which limits the number of satellites the gps can see. If you add some canopy to that it gets tougher.

I am a fan of the History Channel. When they are out mapping Civil War battle fields they use a large external antenna attached to their gps unit. This is not very practical for the hunter. It would be interesting to attach the gps to one of your dog collars. That way you could find out how many miles you are getting per pound of dog food. :wink:

I carry my Legend in a small Lowepro camera case. It is normally zipped-up. When I pull it out the gps is normally locked on some satellites. The case hangs from a strap slung over my head. This has not created any problems in the field. One thing that I do is take a look at the satellite page before I take off. I then carry the gps on the side of my body which has the largest number of satellites. I realize that at times this is not practice. But if you are going North and the majority of the satellites are to the South it is not to difficult to move the case to the 180(6 o'clock) position. I just looked at my satellite page and I have two directly overhead. Three to the East-South East, and one to the West.