Accuracy affected by clouds

Based on what I have learned your problem is the standard receiver built into the eTrex models. I am sure it is a price point issue for Garmin. If you moved up to the 60Cx that unit uses the SiRF High Sensitivity receiver and clouds are a non issue. My c530 has the SiRF receiver and I can pull a signal inside buildings.

My understanding is that, in general clouds shouldn't cause much trouble. What does cause a problem is moisture. Yes, I know clouds are water vapor, but only heavy cloud cover bringing rain should cause a problem. Also water on the ground can cause some issues too. It can cause signal reflection that affects reception.

This is from info I learned from other sites. Seems to me that being on a lake would cause big problems, but there are a lot of marine units out there.

Basically anything that can cause the signal to disperse is a problem. Thick clouds and vegetation both will affect the GPS signal. Newer systems work better, as mentioned. I have both a Zumo and an old eTrex Vista and there is a big difference in speed of signal acquisition and how well they keep signal in bad conditions.

I am brand new to using a GPS. I have the etrex legend. I found cloud cover to also be a problem. I am considering upgrading the unit. Any suggestions would be helpful

The frequency of the signals sent from the GPS satellites was chosen so that they wouldn't be affected by cloud cover and rain.

I've used my iQue 3600 (which doesn't have the new sirf chipset) in torrential downpours while driving on an interstate and didn't notice any difference in accuracy. However, hiking through the woods after a good rain can be a problem since wet leaves can block the signal.

Buy any unit with the SiRF High Sensitivity receiver and your problem is solved.

Take a look at this.

http://gpstracklog.typepad.com/gps_tracklog/2005/09/does_clo...

"The GPS signals will not be affected by clouds, rain, fog, snow, etc., because of the combination of their passing through water vapour, and the signal wavelength meaning they "pass through" rain etc.

On the other hand, water will block/attenuate GPS signals. For example, you can't receive GPS signals underwater, although having a GPS receiver antenna very close to the water surface may allow some reception.

Cloth that covers a GPS receiver's antenna and gets wet (e.g. from rain) can also block/attenuate the GPS signals. In fact, you don't even need the cloth - water on the case that covers the GPS receiver antenna can block/attenuate the GPS signals. That water could be drops, and/or a film of water. I've seen that happen myself, when using my etrex Venture in the rain - the signals were weak/blocked, but a quick drying-off of the GPS case over the antenna brought the reception back, which then degraded again as water accumulated on the case. Similarly, GPS signal reception is degraded in wet forest canopy conditions compared to when the forest canopy is dry."

The consensus seems to be that clouds do not affect sensitivity but that is not the case in my experience. The unit was not wet nor was there any rain or overhead wet leaves. My nuvi 350 with SiRF seems to work well in the rain but I have not had occasion to compare different cloud conditions at the same time and place. If clouds do not affect sensitivity then units with SiRF should not work any better in clouds and units without SiRF should not see a difference in clouds vs no clouds if that is the only difference. I am wondering if it may be that the WAAS is more affected by clouds and that is what causes the accuracy to degrade.

This is copied from http://gpsinformation.net/gpsclouds.htm

Cloud, Rain, Snow, weather in general does NOT attenuate the GPS signals enough to effect accuracy. As can be seen below, the total atmospheric loss (from all causes including rain, clouds, snow, fog, etc.) is but 2db. This is small compared with other variables.

It cites a sorce for info as: http://www.navcen.uscg.gov/pubs/gps/sigspec/default.htm
which would appear to be a long, technical document if you have time to wade through it.

I'm on my third generation GPS, hike extensively with them and driven extensively with them. Sometimes in rainy rain, snow, etc.

If I can get a signal, I'm set - no issues with clouds. Sometimes in heavy forest (but not always) and sometimes in a dense large city next to tall building, I would have a temporary signal problem - but that is about it.