[time-nuts] Position accuracy and Thunderbolt performance
Mark Sims
holrum at hotmail.com
Sun Jul 26 17:45:40 UTC 2009
Ahhh, that's the 64 nanosecond question. I did a lot of self surveys with a geodetic grade antenna over a spot known to within less than a millimeter. Most results were with 6 feet lat/lon 6 meters altitude (hey, can I get a job at JPL landing spacecraft? I can mix english and metric in the same measurement).
But, the key word is most. Some were off over 50 feet lat/lon and 100 meters altitude. Unless you have a known position to compare against you may never know for sure. And, if you have a precisely known location, you can't enter it into the Tbolt with sufficient accuracy since that message uses single precision numbers.
I am doing a couple more tests with a 50 foot error and another with all the error in the altitude (those first two graphs were with lat and lon offset by around 141.4 feet and the altitude exact)
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Or. to put it another way, what could we reasonably expect to see as a position error if the T'bolt is allowed to self survey?
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