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How Accurate is Accurate Enough?
04-11-2021, 02:47 PM (This post was last modified: 04-11-2021 04:03 PM by Dave Shaffer.)
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RE: How Accurate is Accurate Enough?
(04-11-2021 01:15 PM)Chumango Wrote:  Are there real-life calculations where 10, 12, 14 digits are actually required? Or is it a matter of getting more digits and accuracy because we can? Just curious.


I used to support a NASA geodesy program. That program is now measuring relative locations all over the earth to a millimeter or so ( In round numbers, the earth is about 12,740 km in diameter - 10^7 meters. So, 1 mm precision requires parts in 10^11 calculations. All our analysis programs used quadruple precision calculations.

These (NASA and other) systems use hydrogen maser time standards - we worry about stability here at parts in 10^15 - 10^16 (and can measure at that level!). And, current precision in atomic time keeping laboratory standards approaches parts in 10^18!! With such clocks, you can measure the effects of gravity on a clock by comparing clock rates at the bottom and top of tall buildings.
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RE: How Accurate is Accurate Enough? - Dave Shaffer - 04-11-2021 02:47 PM
RE: How Accurate is Accurate Enough? - ttw - 04-11-2021, 03:12 PM

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