Time-of-day satellite reception changes in the house

The constellation of satellites is constantly on the move and your house will have a different amount of satellites overhead throughout the day and night, in your car you have depending on terrain a wider view of the horizon and that will account for the higher accuracy.

Gee, a variation on the order of tens of meters sounds pretty good, considering the GPS birds are orbiting at about 20km!

On a more serious note, a large source of error is still due to distortions of the GPS signal as it passes through the atmosphere (particularly the ionosphere) -- on the order of plus or minus 5 meters. Depending on time of day, your GPS receiver is going to be listening to signals coming through vastly different parts of the atmosphere, for example, some still in sunlight, some in darkness, different humidity levels, all introducing variation.

Military GPS boxes, and very expensive civilian boxes (such as those used in surveying) use multiple GPS frequencies to estimate and correct for these disturbances. Newer GPS birds add a second civilian frequency, so over time, this will be possible for normal people as well, most likely taking things to a meter or so accuracy easily.

I thank you and Flaco for taking the time to respond. How does the WAAS-enabling come about? Is it in every new GPS these days? Would my 880 have that feature builtin?

Once again, Wikipedia is your friend -- they have very good introductory articles on GPS, and on WAAS. (Don't let the math scare you!)

A lot of the Nuvis have WAAS capability, including your 880 (and my 660), but you have to enable it, at least on the 660. Once enabled, look at your satellite status page, and if you see a bird with a number > 31, that's a WAAS signal.

babago, as k6rtm says Wikipedia is your friend indeed. Also you can check out this thread for more WAAS and satellite screen minutiae:
http://www.poi-factory.com/node/13345
...it also contains a link to a web page that has a real-time screen that is every bit as interesting as the Windows defrag screen (which I used to watch, too)

Thanks for that information. So since I have #32 flying my friendly skies, the WAAS must be enabled with no help from me. Thank HEAVEN.....

However, I have no apparent reception but #32 is listed as one of my satellites. What is that little round red object, smaller than the numbered satellites, which goes around the outer perimeter really fast? This little guy doesn't have a number.
I swear he just changed from counter-clock to clockwise rotation!!! Yes, he did change directions.

Honest, I haven't had a THING to drink.

Stand still. That is the last direction of your movement that was detected.

I thought the sats were geostationary, just like the communication sats like DirectTV, etc.

http://en.wikipedia.org/wiki/Wikipedia:Featured_picture_cand... show an animation of the GPS orbits.

The WAAS birds are but not the rest

Look in the sat page of your unit and you will see that over time the same birds are not overhead or if your unit doesn't have a satellite page check out this page and watch it for a period of time and you will see as they move (very boring like watching grass grow) http://www.nstb.tc.faa.gov/RT_WaasSatelliteStatus.htm

Accuracy depends a lot on the geometry of the satellites you're receiving. Best accuracy is when you have satellites clsoer to the horizon on all sides. In the house, most of your satellites being received are probably in the direction of the window limiting the number received and with poor geometry.

I have a lovely night image on my screen now. Sat #32 is coming in fine. NO numbers >32 at all have ever appeared though.

From what I understand, the WAAS-enabled sats have #s >32.

I will take my unit to the other end of the house and set it up in the sunporch there. I want to move my computer out there anyway. And then see if having it in the SOUTHERN exposure makes a difference. We're on the SW side of a hilly area here in NE MASS.

And I don't understand all that I know.
Have a good night, I'm shutting down.