GPS errors due to weather ?

rooster · Posted: Fri Sep 10, 2004 5:51 pm Post subject: GPS errors due to weather ?

Been driving around town today, with "GEONICHE" (v1.2) and the speed, altitude were very hit and miss - at one point we were 300 feet BELOW sea level !!!! Embarassed

Weather is very overcast and rainey - does this effect things ? Last time I used the software it was sunny, and readings were rock solid.

Thanks

Hunnymonster · Posted: Fri Sep 10, 2004 10:12 pm Post subject:

In the last 6 or 7 years of using GPS, I've only ever had a weather-related problem with extremely heavy rain (and I mean extremely heavy - it's only happened to me once or twice in the last two or three years)

Altitude is always the least accurate measure on a GPS, and one reason for that is constant - the GPS system represents the globe as a mathematical model and that model does very from the actual shape of the planet, which doesn't conform exactly to the model created.

Far more likely that your erroneous readings are due to not having a lock on at least 4 satellites (it needs 4 to perfectly solve the 3D position and the time) because with 3, either your position will be miscalculated or your altitude.... the speed reading is usually locally derived based on previous position and current and working out how far apart they are and how long it took to get that far.

delboy0754 · Posted: Sat Sep 11, 2004 5:32 am Post subject: Re: GPS errors due to weather ?

rooster · Posted: Sat Sep 11, 2004 2:37 pm Post subject:

Not using it for nav ! I like the speedo, and height functions...

Dave · Posted: Sat Sep 11, 2004 2:57 pm Post subject:

Speedo should be fairly accurate providing you have a 3D fix (4+ sats), but altitude like others have stated won't be accurate. Not only that but some GPS's don't compensate correctly and also some software don't read altitude correctly.

If you really want an altimeter then you need to use a barometric altimeter like that you will find in some of the more advanced and expensive handheld GPS Receivers based on pressure.

rooster · Posted: Wed Sep 15, 2004 1:05 am Post subject:

That answers it then !!! I must have been so "wowed" with the new toy that I didnt notice the fluctuations ! Embarassed

Speed is very stable - at 5 MPH less than the car speedo, but theres another thead discussing this.

Height is very unstable when stationary... a little more constant when moving, which is odd !! why provide it if its not accurate Evil or Very Mad

Love the new toy - will try geocaching next...

One more question.... my mouse was sold as "duel mode" and "auto switching" what does this mean ? and can I exploit this, or is it at the mouse' decision ?

Thanks for all the help guys.

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