Yo Tom! On Wed, 8 Jun 2016 19:26:21 -0700 "Tom Van Baak" <[email protected]> wrote:
> From one NW GPS farm to another... I'm willing to help you debug > yours. Nothing to debug. I know if I move the antenna I can do better, but it does what I need, and it is near the server that needs it. ntpd caculates precision -22 and the jitter is usually less than 0.5 uSec. More than good enough for my purposes. It makes a dandy Stratum 1 chimer. And 16 meters is not good at all. That is 52 feet! Over just two hours. I bet that gets 2x or more worse over 24 hours. If I cared about location accuracy I would throw away that GPS. Any modern GPS should do way better than that. > > A Garmin 18x reports: > > Altitude Err: +/- 264 ft > > Something is terribly wrong with your setup. The Garmin 18x is much, > much better than this. I know because the 18x was one of the GPS > receivers I brought along on a recent mobile clock experiment. Yes, with good antenna placement it can be better, but the 18x also degrades much quicker than newer GPS when the antenna placement is places badly. > in Tucson: http://leapsecond.com/great2016a/2016a-garmin-18x-2.gif what year is yours? Looking at mine, I see it is actually an 18, not an 18x, so a 12 year old design . Worse than the 18x. > With clear sky view, the peak to peak is under +/- 8 m, and the > (1-sigma) standard deviation is 3 m. Even at the hotel lobby, with > obstructed sky view, the (1-sigma) standard deviation stayed under 7 > m. Your 18x number, +/- 264ft (+/- 80 m), is 10x to 25x worse than > this. It doesn't feel right. My antenna is between two 2 story houses at ground level against a tall hill. It is lucky to get much of a signal at all. I know it would work better in aother location, but it needs to be there next to my main servers. > Off-list, can you send me a day of NMEA from your 18x? Not gpsd > output; but the raw serial ascii data from the receiver. I'd like to > get to the bottom of this. We'll all learn something. I can get you pseudo NMEA, the Garmins work much better in binary mode. When they work in binary mode. :-) I'll start to grab that now. I'll have a 12 hour scatter plot in the morning. While you are waiting check out the attached scatter plot. Now THAT is a good $25 GPS! Beats the heck outta any Garmin. CEP(95) of 1.5 meters over 1,000 seconds. RGDS GARY --------------------------------------------------------------------------- Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703 [email protected] Tel:+1 541 382 8588
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