These terms have appeared in recent exchanges. Keeping the distinction clear is one of my continuing quests. Perhaps I have it wrong, too. I am sure that someone will let me know.
Accuracy is how well a measurement compares to a standard. If my one meter measuring stick is not one meter long, every measurement I make with it will be inaccurate. Precision is the variation among measurements. Even if the measuring stick is absolutely one meter long, every time I make a measurement, I may misplace it a bit. Each realization of the same measurement will be different. In most cases, it is better to be imprecise but accurate than inaccurate but precise. In the former you can be reasonably sure that the "correct" result is in there somewhere. In the latter you can be absolutely sure that your measurement is wrong. A great simplification, but it works with the layman. Now I will take the leap of applying this to time. (Pun intended.) UTC provides precise time intervals for most practical purposes. However, it is inaccurate as the difference between UTC and time scales based on Earth rotation grows. I know precisely at the end of 86,400 SI seconds, that my perception of where I am in space is wrong. This is why we are members of the Precise Time and Time Interval community -- not the Accurate Time and Time Interval Community, I think. Dave Finkleman Senior Scientist Center for Space Standards and Innovation Analytical Graphics, Inc. 7150 Campus Drive Colorado Springs, CO 80920 Phone: 719-510-8282 or 719-321-4780 Fax: 719-573-9079 Discover CSSI data downloads, technical webinars, publications, and outreach events at www.CenterForSpace.com. ************************ _______________________________________________ LEAPSECS mailing list [email protected] http://six.pairlist.net/mailman/listinfo/leapsecs
