McEwen Funeral Home of Monroe

204 South Main Street, Monroe, NC


Thomas Blue McCaskill

August 21, 1938November 1, 2019
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Thomas B. McCaskill, 81, of Unionville passed away at 1:10 p.m. on Friday, November 1, 2019 at Atrium Health Union in Monroe, NC. Tom was born on August 21, 1938 in Lee County, NC, the second child of Clinton and Audrey McKenzie McCaskill. He graduated from Carthage High School in 1956 and received an Associate of Arts degree from Wingate Junior College (now Wingate University) in 1958 and a Bachelor of Science in Engineering Mathematics (honors) from NC State University in 1960. Tom’s professional life included 42 years (1960-2002) as a mathematician and research physicist for the Space Applications Branch of the U.S. Naval Research Laboratory (NRL) in Washington DC. In 1964 he was selected to participate in the NRL Edison Memorial Training Program and completed all required courses for a Ph.D. in Mathematics at the University of Maryland. In 1977 he was reclassified as a Research Physicist. As an NRL scientist, he made key contributions to the design of GPS (Global Positioning System), including the first solution of the instantaneous positioning problem, determination of the optimal inclination for the GPS constellation, and verification of the effects of relativity on an orbiting cesium atomic clock. Tom received five NRL Research Publication Awards, one Patent Award and retired from NRL in 2002 after 42 years of service. Tom was a Senior Member of the Institute of Electrical and Electronic Engineers (IEEE) and member of the Institute of Navigation (ION). In 2003, he was selected by the Institute of Navigation to serve as a Congressional Fellow and in 2005, he became a candidate for U.S. Senator in the Maryland primary election with the Campaign Motto: “GPS Saves Lives.” Tom is survived by his wife of 58 years, Helen Jane Latham of Unionville. From this union there were four children Scot Alexander McCaskill of Unionville, Helen Elizabeth McCaskill (died in infancy), Latham Glenn McCaskill and his wife, Felicia Kantis of St. Louis, MO, David Thomas McCaskill and his wife Lisa Sypula of Alexandria, VA; two grandchildren,Carver Kade McCaskill of Effingham, IL and Matthew Thomas MCCaskill of Alexandria, VA. He is also survived by his five siblings, Robert Hugh McCaskill of Columbia, MD, Frances Elizabeth McCaskill Ward of Edenton, NC, Lydia Alice McCaskill Parker of Little River, SC, James Clinton McCaskill of Pinehurst, NC and John Worthy McCaskill of Greenville, SC. Tom will be remembered by his personal and professional friends from Washington DC and his dear family and friends in NC and surrounding states. The family will receive friends from 4:00 pm to 7:00 pm on Friday, November 8, 2019 at McEwen Funeral Home, 204 S. Main Street, Monroe, NC 28112. A Service of Remembrance will be held at 2:00 pm on Saturday, November 9, 2019 at Union Presbyterian Church, 2000 Union Church Road, Cameron, NC 28326 with The Reverend Dr. R. Shane Owens officiating followed by Interment in the church cemetery. The family will receive friends in the church fellowship hall after the interment. Memorials may be made to Union Presbyterian Church, P.O. Box 898, Carthage, NC 28327.


  • Visitation Friday, November 8, 2019
  • Funeral Service Saturday, November 9, 2019
  • Committal Service Saturday, November 9, 2019


Thomas Blue McCaskill

have a memory or condolence to add?

John Miller

November 13, 2019

My sister (Marie Largay, now deceased) worked for the Space Applications Branch (her whole career) – she spoke about Roger Easton and Tom McCaskill a lot. She worked on data reduction for GPS projects. Her boss in later years (Jay Oaks) gave her a cesium atomic clock (or whatever the land-based receiving unit is called) and it is hanging in the living room of her house at Lake Caroline (now owned by her two daughters). Jay Oaks actually bought his house at Lake Caroline several years before my sister and husband found out about the lake and built their house two doors down from the Oaks.

My sister also worked closely with Jim Buisson. You will see both Oaks and Buisson listed as authors on some of the later entries in the Timeline References. and my sister is listed (M. M. Largay) as a co-author on some of the publications in the Bibliography.

Claudia Youngs

November 9, 2019

I will miss Tom ever present smile, and his kindness. I am honored to have been his neighbor for many years and to have met his wonderful family.
I will miss you Tom, rest in God's grace.
Claudia Youngs

Parker Pappas

November 6, 2019

When I was about six or seven years old, I meet a young boy wondering around the forest as I was. We didn't know each other and wasn't sure about what to do. We decided to become best friends. I was introduced to dad and momma McCaskill and the brothers. For the next many years we spent a lot of time together. Going to church on Sundays, sleep overs and road trips. Dad was a big part of my life and for this I am and always will be thankful to have shared my younger years with my FAMILY. My heart goes out to Helen (Momma), Scot, Lathem and David. I love all of you and I am here for all of you. God Bless y'all,



Thomas B. McCaskill
30 April 2004
Southminster Presbyterian Church, 6-9 May

Spirtual Autobiography

Christian: Presbyterian, confession of faith at age 13. Transferred membership to Southminster Presbyterian Churdi in 1968.
Man: Age 65, 6'2", Caucasian ·
Husband: Married to Helen Jane Latham on 29 July 1961 (42+ years).
Father: Three sons-Scot (38), Latham (34), David (32); daughter­-Helen Elizabeth (June 1968 - 13 August 1968, 54 days - deceased).
Scientist: Research Physicist, U.S. Naval Research Laboratory (1960-2002).
Hobbies: Classical Guitar, Clipping news items of interest (2003 - current)
Most recent book: What Think Ye of Christ? By Judge Felix E. Alley, published 1946
Church activities: Deacon (1970s), Church usher (25 years), Witness Committee (6 years), Prevention of Domestic Violence (1994 - current).

Born in the year of our Lord 193 8 as the second son of Clinton arid Audrey McCaskill on 21 August in Carthage, NC. Six children (Hugh, Thomas, Frances, Lydia, James, John), all currently living. I"1y father ( deceased 1966) was a barber by trade and farmed to supplement income. My mother was the spiritual leader of our family; a housewife until she began working in the Register of Deeds office to supplement family income to help her children attend college, later elected Register of Deeds. Our first son Scot was born on 2 December 1966, and my father died eight days later. My father requested that "Sunrise Tomorrow" be played at his funeral. My mother died in 1971 of breast cancer at age 54.

During my childhood years, our fiunily would attend the Carthage Presbyterian Church. I recall the friendly atmosphere of our church and enjoyed such activities as Bible school. I made my profession of faith and joined the church at age 13.

My introduction into the real world happened on the first day that I went to school. On the first day, many of my classmates cried. During the first recess, Miss Janie McLeod said, "Tommie, you're not crying, why don't you go out to the playground". I did. After I turned the corner at the rear exit to the school a fourth grader attacked me, hit me in the face and bloodied my nose. I went inside, crying. The real difference between the other kids who were crying and me is that I had a bloody nose.

The Carthage Elementary School (through grade eight in those days) was built with a large "U" shape structure, with the open part facing the road. At recess, the boys were restricted to play on the South side and the girls on the North side. Corpora! punishment ( also known as 'The Board of Correction") was used as the penalty for crossing on the girl's side. Fistfights were the order of the day at recess and were not attended or stopped by the teachers. I tried to avoid them but was not always successful. I will never forget my last fight at age 14. The word on the playground was that Billy Brown was "out to fight me". Why, I don't know, but that didn't make any difference. I delayed leaving the school for ½ hour, then left. He was still waiting for me and there were about a dozen spectators. He started the fight; I tried to defend myself but could not. Soon, he had knocked me near unconscious; I was lying on the ground, unable to defend myself He picked up a Coke bottle, broke the top off (it was made of glass), and approached for the kill. One of my classmates, a little 95 pound female named Mary Watson spoke up and said "Billy don't do it". Immediately after that, my sister Frances spoke up. Billy Brown didn't cut or kill me. I am thankful that these young women spoke up to save me; they could not have stopped the fight, but had the courage to speak up for an end to the violence.

In the fall of 1956, I entered Wingate Junior College and enrolled in a pre­engineering curriculum. During my second year at Wingate, I met Helen Jane Latham, who I later married. In the fall of 1958, I entered North Carolina State University as a transfer student and graduated in 1960, with honors, with a degree in Engineering Mathematics. On 6 September 1960, I began working for the U.S. Naval Research Laboratory in Washington, DC. My first project was related to the Navy Space Surveillance System, which is a satellite detection and tracking system. Because of the importance of this project to the Cold War effort, I received a defense deferment.

On 29 July 1961, I married Helen Jane Latham in a religious ceremony held at a Methodist Church in Unionville, NC. In the Washington, DC area, we attended several churches but did not transfer our membership until 1968, after we had moved from an apartment to our home in Fort Washington, MD. We have been actively involved with the Southminster Presbyterian Church for more than 36 years. I was ordained Deacon in the early 1970s, seived on various committees, and later served as usher for more than 25 years. Following a total hip replacement surgery in 1996 and five subsequent joint surgeries, my mobility has been restricted. I currently serve on the Witness Committee and am actively involved in the Prevention of Domestic Violence.

My awareness of domestic violence as a major problem happened in 1994, after I was asked to represent our church at a Presbyterian Peace Making Conference. It took me six years to convince our church to host a "Domestic Violence Seminar" in 2000; in 2001 our church attempted to get domestic violence counseling once per week in Southern Prince Georges County. Although this effort was approved and a memorandum of understanding was signed, we were dropped after a change in administration at the Prince Georges County Family Crisis Center. My work is still focused on the Prevention of Domestic Violence. The next effort will be to (again) invite about 50 churches to take joint action to prevent domestic violence by this fall.

At age 65, I realize that I am near three score and ten years and am doing things like finding a place to be buried and estate planning. Hopefully, this retreat will bring fruit that my wife and I will remember the rest of our lives.

Thomas Blue McCaskill

PART 2-----------------------------------


Thomas McCaskill was born near Carthage, North Carolina in 1938. He grad­uated from Wingate College with an A.A. degree in pre-engineering and from North Carolina State University with a B.S. degree in engineering mathematics, with hon­ors. He is a research physicist who has worked continuously for the Naval Research Laboratory (NRL) since 1960. At NRL he was selected to participate in the Edi­son Memorial Graduate Training program. His graduate work includes studies in mathematics, physics, statistics, optimal estimation, and orbital mechanics.

His first project at NRL was to optically calibrate the U.S. Na val Space Surveil­lance System (NAVSPASUR) satellite detection and tracking system using angular positions that were determined by photographing the Echo satellites against the star background. He later discovered and analyzed an effect on the interferometric mea­surements that led to a patent for a method to determine both angle and altitude from a single tracking station.

In 1964 he began evaluating frequency standards for use in the NRL TIMATION program. In 1966 he began satellite navigation work by graphically determining po­sition fixes and user clock offset using passive range measurements that were plotted on a intercept chart similar to that used in celestial navigation. He then analytically solved the problem of determining a navigator's position using passive range mea­surements and simultaneously synchronizing the navigator's clock with the satellite clock. He received a NRL research publication award in 1971 for his original work on the principles and techniques of satellite navigation. His navigation algorithms and software modules were used in a study made by NRL to select candidate con­stellations for the NRL-proposed design of the Global Positioning System (GPS). He initiated the analysis to optimally determine the constellation inclination that pro­duced the best world-wide PDOP coverage that was later adopted for the operational GPS constellation.

After GPS was declared a system in 1973, two NRL satellites, designated as Nav­igation Technology Satellites (NTS), were orbited to demonstrate key GPS concepts. He helped verify key GPS features such as the worldwide transfer of time via satellite and the experimental verification of the relativistic clock effect on the NTS-2 cesium clock. In 1974 he developed a technique for measuring the frequency stability of an orbiting spacecraft clock and later determined that the NTS-2 cesium clock met the GPS frequency stability specification of 2 x 10 to negative 13. Currently his work involves the on-orbit frequency stability analysis of all GPS Navstar and monitor station clocks.

His publications include 20 NRL reports, of which five have received NRL research publication awards, and 23 published papers. He has made significant contributions to two operational Department of Defense systems: NAVSPASUR and GPS. He is a member of the IEEE and the Institute of Navigation.

Part 3--------------------------------------------

Moore county, N.C. Native Is Leader In Satellites
by Claudia Madeley

Moore County, N.C. Native
Is Leader In Satellites
Claudia Madeley

A Moore County native Is a pioneering scientist of a satellite-based system which can pinpoint locations within 15 yards anywhere on earth an won accolades during Desert Storm.

The Global Positioning System (GPS) may be coming to your "smart" car to get you where you're going In the future. That scientist ls Thomas B. "Tom" McCaskill, the son of the late Moore County Register of Deeds Audrey McCaskill and Clinton McCaskill. He Is a research physlcls1 at the U.S. Naval Research Laboratory Naval Center for Space Technology, Space Applications Branch In Washington, D.C. His specialty Is precise time, frequency, and navigation.
McCaskill, 54, graduated from Carthage High School, obtained a pre-engineering degree from Wingate College and graduated from N.C. State University with honors In engineering mathematics. "My work Is very Satisfying," he said recently. "It turns out GPS - while developed as a military system - is having an enormous Impact on the civilian community."

GPS is composed of n net of 21 solar-powered satellites orbiting around the earth carrying atomic clocks. With a GPS receiver, you are able to fix locations within 15 yards anywhere, Including the ocean, the featureless desert and Jungles without landmarks. GPS sends signals with the speed of light. Adverse weather conditions and night time have no effect on the precision location-finders. They do their magic through sophisticated triangulation which permits three- dimensional position, velocity and time determination in a single piece of equipment. Furthermore, with start and end points available to the user, navigation can be accomplished without the need for charts or observation of any object or reference point other than the display on the receiver which fits in the palm of the hand.

“GPS Is revolutionary. I'm still excited about It even though I've been working toward It for a quarter of a century", McCaskill said. He is one of about 35 people who started developing the concept for the Navy which orbited four technology satellites to prove key navigation and precise time concepts. Later, the best features or the Navy plan were blended with studies by the U.S. Air Force to create GPS. McCaskill estimates now at least several thousand people are working on GPS as well as 50 commercial manufacturers of the GPS receivers. Only three makers now produce government-endorsed anti-spoofing security modules. GPS won commendations as a key war-fighting technology In Desert Storm. Remember the video tapes of allied bombs dropping into the smoke stacks of targets? That was GPS at work. Military authorities say It has changed the face of modem war- are. Ground troops In Desert Storm have said that without GPS they would have been lost most of the time In the featureless Iraqi desert. GPS-aided operations ranged from delivering meals and medicines to guiding unmanned war-heads to their targets.

McCaskill's role In GPS has been to analyze the performance of some 40 of the NAVSTAR space clocks and 10 ground-based clocks located at five GPS monitor stations. He doesn't do It with a screwdriver, however. Instead, he uses a computer to tune the precision Instruments which are "100 million times better than the Bulova Accutron." The clocks are based on an atomic resonance which is supposed to stay fixed, similar to a tuning fork and serves as n reference to a frequency, he explained. "Clocks have a finite life, like people." he commented. One clock lasted 13 yean, while another only 12 days. Each GPS satellite carries four atomic clocks. with one active NAVSTAR clock and three backups. Each NAVSTAR clock In the GPS constellation ls periodically adjusted by commands from the GPS Master Control Station (MCS). The Naval Research Laboratory routinely analyzes the performance of all NAVSTAR clocks for the GPS Joint Program office, and makes special analyses for the MCS whenever a NAVSTAR dock misbehaves.

The GPS receivers used ln Desert Storm cost $4000 each but market demand is expected to lower It to the $500- $600 range for devices that may weigh only two to three pounds, batteries included. Now delivery companies. surveyors, tax assessors and the offshore oil Industry use GPS commercial receivers. For example, a delivery companies would locate an address on a map, convert It to latitude and longitude and use GPS to navigate to that destination. There is still e use for a compass, however, because a GPS receiver can be blocked from getting a satellite signal If it Is taken between two very tall buildings, he added, and the compass would guide until the signal Is resumed

Although pilots don't want to do it because they like to use multiple systems, It would be possible to land a plane In the dark with no runway lights using GPS, McCaskill said. "Smart" cars designed by General Motors with a GPS receiver built In can steer drivers away from clogged roads and do other nifty tricks. A prolonged road test of the "smart" cars Involving multiple vehicles will get underway In Orlando, Florida shortly. In a smart Car, the driver punches in a street address of a local destination. The computer then displays the best route on a six-Inch video screen using GPS, electronic road sensors and video cameras along a highway. If traffic jams or a road blockage appears, the computer will map a new route. Throughout the trip, the computer's synthesized voice gently reminds the driver where the car Is and ought to be. It Is expected that It will be six to eight years before the smart cars will be In widespread use.

McCaskill's first project for the Navy was to optically calibrate Interferometric measurements from the U.S. Naval Space Surveillance System satellite tracking system using the Echo satellite. His first work towards GPS started In 1966 when he determined navigation fixes by plotting ranging measurements taken from the TIMATION J spacecraft on a maneuvering board, similar to that used In celestial navigation. On 17 April 1973 the Naval Research Laboratory's efforts were merged with those of the Air Force to form the Global Positioning System. Two additional spacecraft. called Navigation Technology Satellites (NTS) were orbited to prove key GPS features. On the NTS program for GPS his work included the worldwide transfer of time via satellite and the experimental verification of the relativistic clock effect on the NTS-2 cesium clock. He developed mathematical algorithms that were used for satellite navigation and the determination of the GPS constallatlon parameters. Currently his work involves the on-orbit frequency-stnbillty analysis of GPS NAVST AR clocks.

McCaskill was a recipient ol the Alan Berman Annual Publication Award for 1991 by the Naval Research Lab. He Is the nephew of Myrtle McCaskill Caldwell of Carthage and the late Bessie Pearl McCaskill, the first woman elected In Moore County and register of deeds from 1936- 1952. His father was a well known barber who also raised tobacco, and grew 11 large garden to help feed his family. McCaskill fondly remembers his old scout master In Carthage, Frank Boing, who introduced him to model airplanes and merit badges. The physicist often v1sfts Carthage. Because of the friendly people he Is considering returning to live there after he retires. He said It was "an outsmndlng mathematics teacher at Wingate college" who was pivotal In his career choice.

McCaskill ls married to the former Helen Jane Latham of Union County, N.C.; they are the parents of three sons, Scot, Latham and David. All three sons have attended or are currently attending Western Carolina University. Scot recently graduated with a degree In business communications.

Mrs. McCaskill Is the daughter of a well known agricul¬tural teacher, E.G. Lathan, who graduated from N.C. State University in 1931 and worked contlnuously for 41 years in the same farming community in Union County, N.C. Mrs.McCasklll's degrees are from Wingate College, Appalachian State University, and holds a Masters degree In Counseling Psychology from Bowie State University. She has worked In the fields of education and counseling. Her parents are Mr.
and Mrs. E.G. Latham of Unionville, N.C

This foregoing news story was published In the 28 December 1922 edition of The Pilot.

Part 4----------------------------------
McCaskill design SERVICES


Thomas McCaskill (8/21/1938} is a Research Physicist. He is a native of North Carolina and graduated from Carthage High School in 1956. In 1958 he received an Associate of Arts Degree in pre-engineering from Wingate Junior College (now Wingate University} in Wingate, NC. In 1960, he received a Bachelor of Science in Engineering Mathematics (honors} from North Carolina State University in Raleigh, NC.

Thomas McCaskill served as a scientist for 42 years at the U.S. Naval Research Laboratory (NRL} that is located in Washington, DC. He worked continuously with the Space Applications Branch of NRL from 1960 until his retirement in 2002. His first work was as a Mathematician. After the Global Positioning System (GPS} was established as a Department of Defense space-based navigation and timing system in 1973 he was re-classified as a Research Physicist.

Thomas McCaskill's first work at NRL in 1960 was on a project to optically calibrate the U.S. Navy Space Surveillance System (NSSS} using data collected from the Echo I satellite. On 13 February 1964 he discovered and analyzed an effect using data collected from the Echo I and Echo II satellites that resulted in a co-patent, U.S. Patent 3406397 "Satellite Angle and Altitude Measurement System", with the NSSS system inventor, Mr. Roger L. Easton. Later in 1964 he was selected to participate in the NRL Edison Memorial Graduate Training Program. As a part-time graduate student, he completed all required courses in Mathematics for a PhD at the University of Maryland (College Park, Maryland}, with additional graduate level work in physics, optimal estimation, statistics, and orbital mechanics.

In the fall of 1964 Thomas McCaskill began collateral assignments related to the NRL TIMATION (Time Navigation} program. His first work was to estimate the accuracy of setting the remote station clocks and begin analysis of candidate quartz oscillators that were to be used in the TIMATION-1 satellite that was launched on 31 May 1967. Subsequently he made key contributions to the TIMA­TION program, including the first solution to the instantaneous positioning problem that used a clock in the satellite and a clock in the navigator's receiver. Furthermore, he derived all of the Dilution of Precision (OOP) mathematics that was used to evaluate the performance of candidate constellations for GPS. He deter­mined the optimal inclination for the constellation of satellites that was later adopted for the GPS constellation.

On 2 March 1971 the NRL TIMATION DEVELOPMENT PLAN was published, more than two years before GPS was established as a DOD system on 17 April 1973. The NRL TIMATION DEVELOPMENT PLAN was adopted for the initial architecture for GPS after the Labor Day weekend of 1973 meeting between Mr. Roger L. Easton (Head of the NRL Space Applications Branch) and the first GPS Program Director Colonel Bradford Parkinson (USAF). The TIMATION DEVELOPMENT PLAN included results using a mathematical model that Thomas McCaskill derived and programmed which accounted for the statistical uncertainty of the predicted satellite clock offset as determined by the location of the tracking stations. His contributions are further documented in formal NRL reports, published papers, internal Space Applications Branch Technical Memorandum, and his NRL laboratory note­books. He derived all of the mathematics and wrote the computer program that was used for the transfer of time, via the TIMATION-II satellite, from the U.S. Naval Observatory to the Royal Greenwich Observatory, located in England.

In 1974 Thomas McCaskill was first to derive and program a tech­nique for measuring the frequency stability of the orbiting Navigation Technology Satellite-I (NTS-1} spacecraft clock.

In 1977, following the launch of the Navigation Technology Satellite-II, Thomas McCaskill calculated the observed frequency offset of the NTS-2 cesium atomic clock that was used co experi­mentally verify and correct for the effects of relativity on an atomic clock orbiting at the OPS altitude. Currently, every satellite in the GPS constellation uses a constant relativity-offset frequency correction with the result that the rate of GPS time is the same as UTC (Universal Time Coordinated). NTS-2 was the first opera­tional NAVSTAR GPS satellite.

In 1978 Thomas McCaskill began frequency stability analysis of all GPS Monitor Station and Navstar spacecraft clocks, which were included as part of the reports made to the GPS Master Control Station and GPS Joint Program Office. Subsequently Thomas McCaskill analyzed the performance of more than 100 Navstar atomic clocks that were documented in internal reports and presentations that were made to the GPS ]PO and Master Control Station.

Thomas McCaskill is a Senior member of the IEEE and member of the Institute of Navigation (ION}. He was selected by the ION as a Congressional Fellow in 2003.

In 2005-2006 Thomas McCaskill was a candidate in the Maryland Democratic primary for the office of U.S. Senator.

On 2 March 2007 Thomas McCaskill presented a talk titled "The Global Positioning System" to the Philosophical Society of Washington. The Abstract, Biography, and Minutes of his talk are available on the PSW website archives.

On 3 June 2009 the Naval Research Laboratory published a document co-authored by Thomas McCaskill titled ''NRL GPS Bibliography: An Annotated Bibliography of the Origin and Development of the Global Positioning System at the Naval Research Laboratory". This Bibliography is currently available on the official NRL website as a Special Interest Publication.

part 5----------------------------------

The Global Positioning System
Thomas McCaskill, U.S. Naval Research Laboratory (Retired)
Presented to the Philosophical Society of Washington
2218th Meeting Friday, 2 March 2007 at 8:15pm

The Global Positioning System is a U.S. Department of Defense space-based system consisting of a constellation of Earth-orbiting "Navstar" satellites that provides worldwide navigation and timing information to U.S. and NATO military users, and to millions of civilian users, including the 911 emergency services used to locate cell phones. A GPS user can determine the position and time of a receiver instantaneously, and also its velocity, nearly-instantaneously. Instantaneous positioning with GPS is accomplished by making four, or more, simultaneous passive ranging measurements, using the received signals broadcast by atomic clocks that are synchronized, and syntonized, to a common GPS time, and is functionally related to a four-dimensional space-time defined by three position coordinates and one time coordinate.

Each Navstar satellite continuously broadcasts precise timing signals and a navigation message that is used to calculate the position and clock offset for each satellite tracked by a user's GPS receiver. The orbital elements and the clock offset of each satellite are determined by the GPS Master Control Station using tracking data collected by a network of five tracking stations. The satellites are located in nominally circular orbits of 12-hour period with an inclination of 55 degrees. The principal effects of special and general relativity on the orbiting atomic clocks are constant with a circular orbit and the signals broadcast by each Navstar satellite incorporates a constant frequency offset so that the rate of GPS time is the same as that of Universal Time Coordinated.

About the Author:
Thomas McCaskill received an Associate of Arts Degree from Wingate Junior College n 1958, a Bachelor of Science in Engineering Mathematics from NC State University (honors) in 1960, and then began work as a Mathematician with the Space Applications Branch of the U.S. Naval Research Laboratory. In 1964 he was selected to participate in the NRL Edison Memorial Training Program and completed all required courses for a Ph.D. in Mathematics at the University of Maryland. In 1977 he was reclassified as a Research Physicist. As an NRL scientist, he made key contributions to the design of GPS, including the first solution of the instantaneous positioning problem, determination of the optimal inclination for the GPS constellation, and verification of the effects of relativity on an orbiting cesium atomic clock. McCaskill received five NRL Research Publication Awards, one Patent Award and retired from NRL in 2002 after 42 years of service. He is a Senior Member of the Institute of Electrical and Electronic Engineers (IEEE) and member of the Institute of Navigation (ION). In 2003 he was selected by the Institute of Navigation to serve as a Congressional Fellow. In 2005 he became a candidate for U.S. Senator in the Maryland primary election with the Campaign Mono: GPS Saves LIves

President Ruth McDiarmid called the 2,218th meeting to order at 8: 17 pm March 2, 2007 in the Powell Auditorium of the Cosmos Club. The recording secretary read the minutes of the 2,217th meeting and they were approved.

Ms. McDiarmid made announcements about membership, volunteer help for the Society, and tax exemt contributions. She made the parking announcement.

Ms. McDiarmid then introduced the speaker of the evening, Mr. Thomas McCaskill, retired from the U.S. Naval Research Laboratory. Mr. McCaskill spoke on "The Global Positioning System."

Mr. McCaskill set out to tell us what the GPS is and how it works, about NRL's role in space, and about the revolutionary impact of GPS on our nation and the world. The system enables people to determine position instantaneously and speed nearly instantaneously. The system has, he said, millions of civilian users, including the 911 emergency location function for cell phones.

GPS is run by the Air Force for the Department of Defense. It was designed primarily as a military system but is now available for civilian use also.

He started with a slide showing four satellites, the names of which he knew by heart. These were the first four that, back in 1977, proved the concept would work.

Five clocks are needed to determine position and the clock offset of the OPS receiver. The four satellite clocks are free running, but their times are typically within several hundred microseconds of "GPS time." Data given in the navigation message for each satellite are used to correct for the offset of each satellite clock with respect to GPS time and to compute the position of the satellite, with a correction for the propagation time delay for each of the satellites. The measurements used by the receiver are the apparent time differences between the clock in the receiver and the clocks in the satellites. These differences result from the distance between each satellite and the receiver clock offset. The receiver clock is also free running. Until it takes the different measurements, its variation from GPS time is unknown. A constellation of 28 satellites circles the Earth in 12-hour orbits and provides enough satellites to accurately solve for the four unknowns at the location of any GPS receiver on Earth. The time-delay is about 65 milliseconds for a satellite straight overhead and about 85 milliseconds for one on the horizon.

Passive ranging is fundamental to the system. Passive ranging means that the distance from each satellite is determined without any transmission from the receiver. The synchronization of the satellite clock with the clock in the GPS receiver is what makes this possible. NRL scientist Roger Easton originated and patented this concept that is used by GPS.

There are different methods of getting the initial estimates of location of the receiver and time for the receiver's clock. One has the receiver operator choose the nearest city from a list of I 00 cities around the world. A method Mr. McCaskill developed averages the vectors to all the satellites detected by the receiver.

Two carrier frequencies are used to transmit from the satellites. The timing information is broadcast using pseudo-random noise codes. These codes, which are different for each satellite and orthogonal to each other, are used by the receiver to distinguish among the satellite signals. Mr. McCaskill demonstrated this using volunteers vocalizing from different parts of the room. We found we could distinguish among the voices, even when several were sounding at once.

Time prevents a detailed review of the mathematics of the determination of time and locations. However, it is a logically similar to one of those puzzles about the age of children. If Adam is two years older than Blake, Blake is twice as old as Carrie, and Carrie is 1/3 as old as Adam, how old is Carrie? If you have enough information about the differences, you can determine the ages of them all. In the GPS, location is related to time differences from the satellites, so location can also be determined.

Many people see GPS as a new and different thing. Mr. McCaskill sees it as a result of a long history of the Naval Research Laboratory and its role in work on navigation.

Navigation by time goes back a long time. He recalled the work of John Harrison. the British man who invented a clock that would keep time at sea accurately enough to use in determining longitude. That was in the mid l 700's. That type of device was used for 200 years until the development of electronic clocks and atomic clocks in the mid 1900's. NRL took delivery of the first commercially produced cesium atomic clock in 1955. In 1974 the first atomic clock orbited the Earth in a satellite built by NRL.

NRL was established in 1923 on the recommendation of Thomas Edison, whose statue stands at the entrance. It started with two divisions, radio and sound. In 1998 it celebrated its 75th anniversary. Among its contributions, it counted the Minitrack System (used to track Vanguard satellites), the Vanguard program, the Navy Space Surveillance System, the Timation Program, and the Global Positioning System.

After World War II, NRL participated in the V-2 , research program at the invitation of the U.S. Army. NRL designed 80 different scientific experiments, with instrumentation that was placed into the nose cone of the captured German rockets. These produced the first direct measurement of atmospheric pressure above 18 miles, the first photos of Earth from 40, 70, and IO I miles up, the first photos of the ultraviolet solar spectrum below 285 angstroms, the first detection of X rays from the Sun, and other notable milestones. Those V-2 launches were the birth of space-based astronomy and the Navy's space program. NRL proceeded to develop its own rockets, Mr. McCaskill said, " ... when it became evident that the supply of V-2 rockets would be exhausted."

He turned to "war stories" about GPS. In Desert Storm (the first "Gulf War") troops were found using their own Visa cards to buy receivers for about $3,500 because not enough military GPS receivers were available. In WWII, less than 5% of bombs hit their targets. Now ships, aircraft, tanks, and troops launch precision guided munitions and track their positions precisely. We now see a possibility of wars fought with robots rather than human beings.

In 2003, nine men were trapped in a mine in Pennsylvania for 77 hours. Rescue workers, using GPS, were able to drill a 6-inch air hole to their location to keep them alive until a larger, 22-inch, shaft could be drilled and a rescue capsule lowered.

There are many examples of GPS saving lives, not all of them recounted in General Motors Onstar ads. Mr. McCaskill hopes he will live long enough to ride in an automobile piloted by GPS.

He closed by saying that we have the most powerful nation on God's Earth. What the future will be depends on all of us working together.

In the question-and...answer session, he amplified that clock accuracy is a basic requirement so that we were able to use GPS for a 180-day war. So much military function depends on GPS to provide location ability without a tracking system.

He stated that we could build automatic cars now. Robotic autos, he "guaranteed," would do better than 99% of all the drunks on the highway.

Asked if a quantum positioning system could make GPS more accurate, he said he thought it would, but he wasn't sure it would be cost-effective. He did offer hope that it might help us determine what is happening at the nanometer level.

Should we expect any effects of daylight saving time? No, he said - GPS time does not use DST at all.

He was asked why, with such an ability to determine facts on the ground from space, we did not have a better assessment of the situation in Iraq before we invaded. Mr. McCaskill pointed out that the determination of facts and the assessment of the overall situation are different things. He said that while he was a government employee the Hatch Act covered him and he avoided partisan political statements.

He was asked about atmospheric effects on passive ranging. He said the measurements are corrected for ionospheric delay and atmospheric anomalies. Without those corrections, the system could only determine location to within 60 - 70 meters.

Ms. McDiarmid thanked our speaker. She presented a plaque commemorating the occasion and awarded him a year's membership in the Society. Finally, at 9:48 pm, she adjourned the 2,2 I 8th meeting to the Social Hour.

Attendance: 59
Weather: Very clear, beautiful, with a slight breeze that felt like it came from the Gulf
Temperature: 11c

Respectfully submitted,
Ronald 0. Hietala Recording secretary © March, 2007

The following was accompanied by formulas that will not print in this book:
Instantaneous Navigation Mathematics
NRL formulated and implemented a solution to the problem of instantaneous naviga­tion using artificial satellites by passive ranging.

The following, part of the above article, accompanied diagrams that will not print in this book:
Formulation of Dilution of Precision (DOP) measures
The fundamental equation for DOP studies at NRL were defined by Equation 50, NRL 7252, published in June, 1971. Different formula­tions ofDOP were used, depending on the solutions of interest: 4D instantaneous, 3D instantaneous with good clock, or 2D with altitude constraint.

DOP results for the navigation satellite constellation study were pre­sented in June, 1972 (NRL 7389) for the solutions listed above.

The Geometric Dilution of Precision (GDOP) represents the overall solution of uncertainty per unit of observation noise (McCaskill- 1976, p. 170.)

Additional DOP forumulations were defined and used to measure particular uncertainties, for example, PDOP (position), VDOP (verti­cal, altitude, or Z-component), HDOP (horizontal), and TDOP (time). (See NRL7581, for example, for formulae, and NRL7581 for plotted results for a constellation study.)

Evaluation of PDOD, showing clear advantage of 12-hour orbits for realizing the advantages of atomic clocks. (NRL 722 7.)