Bad GPS reception in very cloudy/stormy weather, truth or myth?

[+HaLiJuSaPa]

During Friday's sleet/snow storm here in the Northeast I took a 5 block walk from my condo to a convenience store to get a few things and took my GPS (Lowrance iFinder GO) along for curiousity. It had the worst "out in the open" performance I had ever seen. It took a good 10 minutes to get a fix and it tended to bounce my speed and position quite inaccurately (with EPE's in the high 3 and low 4 digits, like 1000 ft.) and kept showing my altitude as about 100 ft. below sea level (I know that altitude is not as accurate as speed and position on most GPSr's, but my neighborhood is about 150 ft. above sea level and it usually shows a reading between 100 and 200 there). There are not a lot of trees or tall buildings to bounce the signals so that was not a major factor.

 

I had just used it 3 days prior when it was sunny and 70 deg out with no problem, so I don't think almanac issues came into play. I also had Energizer Lithium AA's in it yesterday, so the 25-30 deg temps were probably not the problem either.

 

My best guess was the very thick cloud cover and weather. I have only seen this behavior before in extreme reception conditions (very tall buildings, very heavy tree cover). But I have read lots of articles that seem to suggest that clouds do not affect reception and that the idea of GPSr's not working well in very cloudy weather is a myth. Yet both of my brother-in-laws (who got me and their sister into geocaching) think that they DO affect reception, one of them went for a cache a few days prior in very cloudy/foggy weather and had "bounce" issues as well (with a Garmin Legend, non-Cx version).

 

What is the scoop here? Thanks for your help.

[Grasscatcher]

Go to Trimble site Trimble Planning and download that free software. With it, you can very likely answer your own question why you got bad reception at a certain time and at a certain location.

 

You can tell how many and which specific satellites your unit will be seeing at any given time and see that there are times that you should EXPECT to get lousy reception and therefore lousy accuracy. (Note: it's not cloudy weather)

 

That being said....When there is extremely heavy wet snow falling at the time, that can also affect reception due to multi-path error, which is the result of satellite signal reflection.

 

Also on the Trimble home site look for a reference to their GPS tutorial. VERY educational....

Edited March 18, 2007 by Grasscatcher

[+HaLiJuSaPa]

Go to Trimble site Trimble Planning and download that free software. With it, you can very likely answer your own question why you got bad reception at a certain time and at a certain location.

 

You can tell how many and which specific satellites your unit will be seeing at any given time and see that there are times that you should EXPECT to get lousy reception and therefore lousy accuracy. (Note: it's not cloudy weather)

 

That being said....When there is extremely heavy wet snow falling at the time, that can also affect reception due to multi-path error, which is the result of satellite signal reflection.

 

Also on the Trimble home site look for a reference to their GPS tutorial. VERY educational....

 

Thanks. The satellite geometry on my screen did look extremely odd that day, so I'm sure that helped too.

 

Just curious when you say "satellite signal reflect in extreme heavy wet snow", where would the signals bounce, off the falling snow and sleet?

 

I wonder if cold weather in and of itself helps to ruin reception (other than batteries)? I remember another cold day (but sunny) where I had problems outside, but inside my mom's house (where unlike where I live, which is the bottom floor of a 7-story building, I get perfect indoor" reception) just an hour or so later.

[+Prime Suspect]

Rain, sleet, snow will not affect reception to any degree that a person could notice.

The frequencies used by the GPS system were specifically chosen because they are not affected by rain, etc.

 

Read more here.

[+HaLiJuSaPa]

Rain, sleet, snow will not affect reception to any degree that a person could notice.

The frequencies used by the GPS system were specifically chosen because they are not affected by rain, etc.

 

Read more here.

 

HMM, maybe it was the water that got on the GPS from the sleet and all......

[+stache88]

I own a Garmin Legend (non CX) and I find it seems to work better in bad weather. It aquires more satellites and is more accurate. In fact I've had the best accuracy (8ft) in a downpour. I was out yesterday in a snow storm in the woods and was consistantly aquiring from 8 to 11 satellites. On a hot day in the summer in a wooded area my GPS was jumping all other the place. So from my experience, as odd as it seems , the worse the weather the better the GPS.

Edited March 18, 2007 by stache88

[+NightPilot]

Neither rain, nor sleet, nor snow, nor gloom of night will prevent the GPS from working. Water covering the antenna, however, will block the signals. As will the water in your hand or any other part of your body.

[+Renegade Knight]

I have been caching in the fog when the GPS would not settle down, would not get within 50' of the cache and generally just acted goofy.

 

Others have made and sold me on convincing arguments as to how a GPS works in all kinds of weather. However I still have a GPS that was just goofy. The extra water coating all the trees and the like is the only explanation that I could find. Rain doesn't stop a signal but water in a tree canopy or your own body will.