[Loadstone] Interesting observation on altitude.

[Farfar Carlson]

Can be. Depends on your receiver. Also note that in the triangulation method used by satellites to find position, the most accurate, due to the angle of elevation, is the ex-y coordinates on the surface (lon and lat). 

The least accurate, again due to the elevation angle of the satellite constellation will be altitude (the z-axis). It's very hard to get a good altitude measurement  when you're looking down at a point on the ground. All the factors of delay in signal propagation will stack up to reduce precision.

Based on trigonometry the most accurate measurement of altitude would be a constellation of satellites sitting on the earth's surface, and looking "up" at the GPS receiver. That's not the way orbiting satellites work, I'm afraid.

Dave
Created in the Audio Recording and Mixing Studios, San Jose, California


  ----- Original Message ----- 
  From: Dale Leavens 
  To: loadstone at loadstone-gps.com 
  Sent: Saturday, August 21, 2010 06:37
  Subject: [Loadstone] Interesting observation on altitude.


  Yesterday I was sitting here at my dining room table charging my M1000. I brought up Loadstone on the phone. Although standing still it was interesting to notice that altitude started at a little better than 97 meters and over the course of half an hour descended to about 76 meters. Accuracy was reported at between 7 and 9 meters depending when I looked.

  Pressing #3 announced 3 dimensional fix. I don't know what that actually means but I assume the third dimension to be vertical.

  Is this much drift usual?

  Thanks.

  Dale Leavens.


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