Tag Archives: Allan Variance

GPS Accurate to a Centimeter

How to find peace, love, and joy in the midst of the storms ahead in all that we do:

I have chosen to include God in all that I do, and that has made all the difference in my life.  I have learned that as we ask, seek, and knock (Matt. 7:7), God will put thoughts into our minds and inspire our doings.  I believe my master’s thesis, which gave birth to the Allan variance (AVAR), was inspired by God: Allan Variance – Spirit of Revelation | It’s About Time (itsabouttimebook.com).  Similar experiences have occurred over my professional career, and I give God the glory.  As an example, before I retired from the lab in Boulder, I was pondering on the problem of the inaccuracies in determining the positions of the GPS satellites; the vertical error component is the largest.  And the idea came into my mind that Kepler’s Third Law could solve this problem.  I asked my good friend, Professor Neil Ashby, to help me do the simulations.  We got some impressive results and presented a paper in the UK and later at an Institute of Navigation GPS conference in 2001 in Salt Lake City, UT: A New Paradigm for High Accuracy Orbit Determination at the Centimeter Level (allanstime.com).
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What Time Is It?

How many times have you asked, “What time is it?”

Einstein is reported as saying, “If you ask me what time it is, I will tell you, but if you ask me what is time, I cannot!”  If he didn’t say it, he should have!

Time, as we think of it flowing throughout the universe is a metaphysical concept – abstract – an idea in our minds.

Some Fun With Time and Some Mind Benders

  1. Doc says, “Joe, I got some bad news for you. You’ve got six months to live.” Joe says, “Six months? Doc, I can’t pay your bill in six months, I can’t do it!” Doc says, “OK, I give you a year…”
  2. Chinese kid was born before the due date. Parents named him Sudden Lee.
    Did you hear about that guy who fell into the infinity pool? Yeah… it took him forever to get out.
  3. The future, the present and the past were arrested and sentenced, and things got tense.
  4. Moses had the first tablet that could connect to the cloud.
  5. Why do the French eat snails? They don’t like fast food.
  6. Here is one for you; a twelve hour stopped clock is perfect twice a day!  And if you could make it go backwards infinitely fast, it would always read the correct time!
  7. True story: I noticed by smart phone was receiving responses to my text messages 4 minutes before I sent them out.  Being a time guy, I asked, “How could this be?”  My wife and I got a good laugh about why this might be: “mind readers!”  I discovered my phone was in manual mode and had gained 4 minutes since I bought it over a year ago.  I fixed it!  Cell towers are synchronized to GPS, so now I am with you; not a head of you!
  8. Another true story: My wife and I celebrated our 22nd wedding anniversary in Guam on the 20th of February, 1981.  I had been invited to give a talk in New Delhi about precise time and frequency distribution systems; the UN had paid for my ticket, and I obtained a $50 coupon to buy a second ticket for Edna.  So we arranged that after the conference, we would travel on to Guam to celebrate the 20th; we had a great time in Guam.  We got on the plane that evening and arrived in Hawaii the next morning, and it was the 20th of February all over again.  Two anniversaries in a row; can’t beat that.  Who but a time-nut would have planned that so?  A little time warp due to our spinning earth and our mixed up timing system.  I have a solution for that in my book: It’s About Time.

What is TIME?

Man’s time is not time; it is time-interval – the accumulation of time-intervals, like a second, a minute, an hour, a season, a calendar, a span from some origin or point in time (like the birth of Christ). We measure time in our minds.  A lot of people think time seems to be going faster.

For example, time can feel slow or “stand still” when you are waiting for a loved one to come out of surgery or when you are waiting for a response after a job interview.  Days can seem long when you are lonely or sad.

On the other hand, we seem to lose track of time when we are busy. “Time flies” when you are having fun, actively engaged in an event or circumstance that is fulfilling or when you are happy.  Vacations seem all too short.

Time seems to collapse (time warp) when you meet an old friend that you have not seen in 25 years. You may feel like it was just yesterday that you were together.

Nothing demonstrates the flawed notion of time better than aging. A young person may think that 30 is over the hill. A 50 year old may feel am 80 year old is ready to die.  And a 70 year old looks in the mirror and can’t believe what they see because inside they feel like a 20 year old.  I am 82 years young, and feel a lot of life is ahead of me — its exciting!

Making some sense of “Time” on this planet

One of the best definition of time that I know of is from my good friend, Prof. Chauncey Riddle, “Time seems to be the possibility of change.”

The Allan variance is the optimum estimator of change in the rate of an ideal atomic clock. http://itsabouttimebook.com/allan-variance-in-laymans-terms/  We cannot measure time, since it is metaphysical, but we can measure time interval more precisely than anything else.

The four dimensions of Einstein’s theory (space and time) are mortal constraints.  Einstein includes man’s time in his relativity equations, and his theory makes GPS work as well as it does.  We contracted with Professor Neil Ashby to develop the relativity equations for GPS.

We also have done a Unified Field Theory experiment showing evidence of a fifth dimension, which we call the eternity domain.  Man’s time is not a constraint in this domain, and this is where God and His angels do their work, and it is where we couple when we pray. The infinite atonement of our Lord and Savior is operative from this eternity domain and covers us in our mortal journey.

God’s Time is Eternal

Remember, God is without constraint. God’s time is eternal. It has no beginning and no end.  God’s TIME has its full purpose in bringing “to pass the immortality and eternal life of man.”  (Moses 1:39)  Christ overcame death and hell – providing resurrection for all and eternal life – life with God and life like God – for all who will believe in Him and accept of His glorious gospel message.  How blessed we are to have the fullness thereof.  Let us live it and share it making the best use of time that we may enjoy eternity.

David W. Allan



























David W Allan – The Allan Variance

The Allan Variance is perhaps the most famous of David W. Allan’s achievements, with its derivative for telecom:  TDEV, the Time Deviation.

In 1965, Mr. Allan’s Master’s thesis gave birth to what the world knows as the Allan variance, the efficient technique for characterizing the performance of clocks and for knowing how to optimally use them in time keeping, and for which he is best known.   Because the Allan variance is used in characterizing the performance of atomic clocks, it was used extensively to sort out the performance of atomic clocks used for GPS to meet the stringent specifications for that navigation and timing system.

World Recognition

David Allan is as well recognized in the field of time and frequency technology as any other figure in the world. He helped to develop our nation’s official time and frequency standards based on atomic clocks and wrote the algorithm for keeping time for the United States.  He spent many man-years helping in the actual development of GPS. He also helped other nations with their official time standards, as well as helping with International Atomic Time and Universal Time Coordinated (UTC), which is official time for the world as kept at the BIPM (International Bureau of Weights and Measures) in Paris.
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Celebrating the 50th Anniversary of the Allan Variance

250px-David_W._Allan,_croppedI just received word of the publication of a “Special Issue on Celebrating the 50th Anniversary of the Allan Variance.”

On May 10th, I will be received the highest award IEEE gives at an an international meeting (International Frequency Control Symposium) in New Orleans, LA, on the 10th of May for my life-long contributions.  The citation reads, “For seminal work to the UFFC community regarding time determination, time prediction, time dissemination and timekeeping through contributions to atomic frequency standards, space-based navigation, time and frequency stability analysis, time-scale algorithms, and timekeeping devices.”
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