Transiting to GPS and beyond

September 23, 2020  - By
Headshot: Terry Moore

Terry Moore, professor emeritus, University of Nottingham

The end of July was quite a momentous occasion for me as I accepted the offer of voluntary redundancy from the University of Nottingham after almost 35 years of employment. If I then add the six years I spent at Nottingham as an undergraduate and then as a postgraduate student, that totals almost 41 years of my life spent at the university.

I guess it is not surprising that recently I have spent some time reflecting on those years and the changes that have occurred in positioning and navigation throughout that long period. My first degree was in civil engineering, although I did specialize in land surveying in the final year.

Professor Ashkenazi. My first contact with satellite navigation was early in 1981, when Professor Vidal Ashkenazi, later my mentor and good friend, brought a JMR-1 Transit Doppler NAVSAT receiver into our second-year surveying lectures. That gentle repetitive beep as the receiver tracked the Transit satellites had me hooked for life. I don’t think I realized then that navigation and positioning would be the focus of my working life, but I was fascinated by the technology and prospects, and it really was one of those life-changing moments.

1984: Texas Instruments TI-4100. (Photo: NOAA National Geodetic Survey)

1984: Texas Instruments TI-4100. (Photo: NOAA National Geodetic Survey)

My Ph.D. continued in surveying and geodesy, and the focus was on the precise orbit determination of the LAGEOS geodetic satellite using Satellite Laser Ranging measurements. The goal was to investigate the determination of Earth Rotation Parameters (the Polar Motion and diurnal spin of the Earth) as part of an international collaboration known as Project MERIT.

Using Transit. I remember taking a Magnavox MX 1502 Transit receiver down to a conference at Herstmonceux Castle, and over the weekend I set up the instrument in my parent’s back garden in Sheffield, much to their amazement.

2020: Garmin Fenix6 smartwatch. (Photo: Garmin)

2020: Garmin Fenix6 smartwatch. (Photo: Garmin)

I did not start working on GPS until 1985, through my post-doc research position, sponsored by British Petroleum. This was investigating the first uses of GPS within the oil-and-gas sector for precise offshore positioning on platforms and survey vessels. The early GPS receivers we used were the Texas Instruments TI-4100 receivers, of which we borrowed five for the first long survey campaign to measure precise heights down the East Coast of England and Scotland. What a “pleasure” they were to use. I remember manually typing in the elements of the almanac for the receiver to acquire one satellite at a time.

Soon after we bought our first two Wild-Magnavox WM-101 receivers, which looked to be masquerading as Samsonite luggage. And now here I sit typing this article with GNSS receivers in the Garmin watch on my wrist and the Samsung phone beside me on the desk.

Last weekend, I was walking in the Lake District of England with my wife and daughter, and I did a quick count of our GNSS receivers. We had eight GNSS receivers (in watches, phones and handheld receivers) between the three of us, and of course there were others in our cars and the cycling GNSS receivers all nearby. How things have changed and how could we have imagined such as staggering growth in the ubiquity of GPS, and now GNSS, over those past 35 years.