gps outage predictor

Eli · 03-09-2010, 8:39 PM

Hi,

I am working on a phone app which uses gps. I would like to understand better the fluctuations that I am seeing in the gps signal. I have found software which can predict gps coverage for a certain location. Is there such a thing as a web site where you can enter your location and it will tell you if there are any predicted outages in the coming day or week?

Thanks,

Eli

HumVee · 03-09-2010, 10:02 PM

Why would there be outages based on time? I was under the impression that the 24 GPS satellites orbiting the Earth had orbits that would pretty much guarantee that your GPS unit would see at least 4 birds at any given moment. Even when I'm in my house, my GPS has never reported less than 8 satellite locks, and outside I get 10 - 12.

What does impact GPS coordinate calculations and reporting for me is objects that block off significant parts of the sky - tall buildings, cliff walls, dense woods, etc. It's interesting to me that I have better reception in my house than I do in the woods...it must be that living trees are more effective at blocking satellite signals than drywall, plywood & roof shingles....

Eli · 03-10-2010, 6:19 AM

Thanks for the reply.

From what I have read the 24 satellites in orbit should be enough to provide roughly 8 visible satellites in view at all times. As shown in this animation.

File:ConstellationGPS.gif - Wikipedia, the free encyclopedia

My experience is that gps has good days and bad days. At first I thought that it was weather related. But, there have been plenty of blue sky days when my phone ( moto droid ) couldn't get a fix at all. And, conversely some cloudy days when I have had a perfect gps lock all day. Over time I have begun to notice that the periods of time when the gps signal is weak last for 24-48 hours. This lead me to wonder if the gps coverage from the satellites wasn't perfect and occasional dead zones would occur.

I found the following site which talks about gps outages. Apparently all flights check for outages along there flight plan?

GPS RAIM PREDICTION

GPS RAIM PREDICTION - Grid Display Tool

The above site and "grid tool" is cumbersome and geared towards aviation. This is why I am looking for a "pedestrian" version. Perhaps a web based gps predictor. If such a thing even exists.

There must be some explanation for these good days and bad days.

Thanks.

zee · 03-10-2010, 9:21 AM

If I do this right, a url should appear that will keep you busy for a spell. Check out several choices on the upper left. If I goof, I'll have to come back and hunt & peck in the url.
GPS Almanac Information - USCG Navigation Center

Eli · 03-10-2010, 9:29 AM

The Coast Guard!!!!! I should have thought of that!

Thanks.

03-09-2010, 8:39 PM	#1
Eli Join Date: Mar 09 2010 Location: Maine Posts: 4	gps outage predictor Hi, I am working on a phone app which uses gps. I would like to understand better the fluctuations that I am seeing in the gps signal. I have found software which can predict gps coverage for a certain location. Is there such a thing as a web site where you can enter your location and it will tell you if there are any predicted outages in the coming day or week? Thanks, Eli

03-09-2010, 10:02 PM	#2
HumVee Join Date: May 11 2009 Location: Portland, Oregon Posts: 1,254	Re: gps outage predictor Why would there be outages based on time? I was under the impression that the 24 GPS satellites orbiting the Earth had orbits that would pretty much guarantee that your GPS unit would see at least 4 birds at any given moment. Even when I'm in my house, my GPS has never reported less than 8 satellite locks, and outside I get 10 - 12. What does impact GPS coordinate calculations and reporting for me is objects that block off significant parts of the sky - tall buildings, cliff walls, dense woods, etc. It's interesting to me that I have better reception in my house than I do in the woods...it must be that living trees are more effective at blocking satellite signals than drywall, plywood & roof shingles....

03-10-2010, 6:19 AM	#3
Eli Join Date: Mar 09 2010 Location: Maine Posts: 4	Re: gps outage predictor Thanks for the reply. From what I have read the 24 satellites in orbit should be enough to provide roughly 8 visible satellites in view at all times. As shown in this animation. File:ConstellationGPS.gif - Wikipedia, the free encyclopedia My experience is that gps has good days and bad days. At first I thought that it was weather related. But, there have been plenty of blue sky days when my phone ( moto droid ) couldn't get a fix at all. And, conversely some cloudy days when I have had a perfect gps lock all day. Over time I have begun to notice that the periods of time when the gps signal is weak last for 24-48 hours. This lead me to wonder if the gps coverage from the satellites wasn't perfect and occasional dead zones would occur. I found the following site which talks about gps outages. Apparently all flights check for outages along there flight plan? GPS RAIM PREDICTION GPS RAIM PREDICTION - Grid Display Tool The above site and "grid tool" is cumbersome and geared towards aviation. This is why I am looking for a "pedestrian" version. Perhaps a web based gps predictor. If such a thing even exists. There must be some explanation for these good days and bad days. Thanks.

03-10-2010, 9:21 AM	#4
zee Join Date: Feb 10 2010 Location: USA Posts: 90	Re: gps outage predictor If I do this right, a url should appear that will keep you busy for a spell. Check out several choices on the upper left. If I goof, I'll have to come back and hunt & peck in the url. GPS Almanac Information - USCG Navigation Center

03-10-2010, 9:29 AM	#5
Eli Join Date: Mar 09 2010 Location: Maine Posts: 4	Re: gps outage predictor The Coast Guard!!!!! I should have thought of that! Thanks.

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