The end of 2007 saw the deaths of two individuals who were intimately involved in the development of the Tellurometer.
When Trevor Wadley was working on the Tellurometer at the Telecommunications Research Laboratory (TRL) in the mid 1950s, he was under the guidance of Frank Hewitt who was the director of that laboratory within the CSIR in Johannesburg. Hence there was close cooperation between the two of them at all stages of the development and testing of this revolutionary instrument. Hewitt was also closely involved in another of Wadley's inventions, the Wadley loop radio receiver RA17 and in particular in the arrangements with RACAL to develop and market this very successful unit.
Dick Hölscher, also at TRL, was to come to notice particularly in the mid 1960s when Tellurometer developed an infrared instrument especially for use in measuring short distances for survey purposes. This was at just about the time that Wadley was to retire from the TRL and join the Board of RACAL. In 1967 and 1970 Hölscher was to write two important papers on the use of GaAs light emitting diodes in EDM equipment. [1,2]
Dr. Francis John Hewitt
Dr. Francis John Hewitt passed away on 22 December 2007 in Canada. Born in Grahamstown, on 24 November 1919, he matriculated at St Andrews College and at age 19 graduated from Rhodes University. On obtaining both a BSc and MSc in the same year he was awarded a scholarship to Cambridge University. However, with the beginning of hostilities, instead of going there he joined the SA Air Force and was assigned to the Special Signals Services (SSS), a small, secretive unit, headed by Dr. Basil Schonland and charged with developing radar.
The unit served in Kenya, Sinai, West Africa and along the coast of South Africa. Towards the end of the war he was appointed as South African Liaison Officer in England.
At the end of hostilities Dr. Schonland founded the South African Council for Scientific and Industrial Research (CSIR) and appointed Hewitt as principal research officer for the Telecommunications Research Laboratory (TRL) based at the University of the Witwatersrand. This laboratory was staffed inter alia by nine former members of the SSS. Hewitt's initial remit was to use radar to study interstroke processes in lightning, for which he was awarded a PhD.
Among his staff was Trevor Wadley who developed a new ionosphere sounder, studied radio propagation through rocks and developed a revolutionary new radio receiver capable of the accurate determination of radio frequencies. As the Racal RA 17 it became standard use with the British military forces. In particular Wadley, under Hewitt's direction, developed the Tellurometer for measuring distances of 60 or more kilometres to accuracies of a few centimetres - an instrument that is still in wide use today. Hewitt also played a noticeable role in promoting the instrument and arranging for its manufacture and patent rights.
When, in 1960, the TRL was upgraded to a National Institute of Telecommunications Research, Hewitt was appointed its director. It was here that Hölscher, under Hewitt's guidance, developed the MA 100, an infra-red version of the Tellurometer, which gained widespread use for accurate distance measurement over shorter (2 to 3 km) distances. Hewitt also oversaw a revolutionary radio system to obtain time-resolved, 3D images of lightning flashes otherwise hidden by cloud and rain. This allowed lightning and thunderstorms to be studied in detail.
In 1964 Hewitt was appointed a vice president of the CSIR and deputy president in 1969. It was then that he negotiated with the SRC in the UK to form a joint venture that established the South African Astronomical Observatory (SAAO) near Sutherland in Cape Province. He was also responsible for all South African aspects of two major deep space tracking stations operated near Johannesburg (Hartebeeshoek) for NASA between 1964 and the mid 1970s. When these facilities were abandoned in 1973 Hewitt arranged for the abandoned hardware to be converted to a South African Radio Astronomy Observatory, and for another abandoned site to be converted to a South African Centre for Remote Sensing.
Frank Hewitt was a true internationalist in the field of science. His position as South African Radar Liaison Officer at the end of World War II brought him into contact with many of the future leaders in the growing field of radio science. He represented South Africa at general assemblies of the International Scientific Radio Union (URSI) and the Committee on Space Research (COSPAR). He established a national committee for the International Astronomical Union (IAU) to bring astronomers together at a critical time when various foreign-funded observatories in South Africa were closing their facilities, prior to the establishment of the SAAO. He constantly strived to promote South African interests in international scientific activities and was well respected among his international peers.
Throughout his life Frank demonstrated amazing energy for all sorts of creative projects including boat building, home furniture, hobby farming and at one stage even a swimming pool. After retiring in 1980, he relished having more time for such projects, at the same time staying active in the scientific community. He was awarded two honorary science doctorates, one from his alma mater, Rhodes University, and the other from the University of the Witwatersrand. He also received numerous awards for his contributions to science, including the prestigious South Africa Medal from the South African Association for the Advancement of Science in 1987.
Dr. Dirk Hölscher
Dr. Hobbe Dirk Hölscher, well known as Dick Hölscher, the engineer who developed the infrared version of the Tellurometer, died in Pretoria, on 2 December 2007 aged 79 years.
Dr. Hölscher was born in Ziest, Holland in 1928, and immigrated to South Africa in 1929. He matriculated at Helpmekaar Hoërskool in Johannesburg in 1945, then enrolled at the University of the Witwatersrand where he graduated in electrical engineering in 1949. After a year with a private engineering firm he joined the Telecommunications Research Laboratory (TRL) of the CSIR. This laboratory was housed in the Electrical Engineering Block of the University of Witwatersrand.
In 1955 Hölscher was sent by CSIR to work on attachment for two years at the Telecommunications Research Establishment in Great Malvern, England with the specific object of becoming fully familiar with solid state technology. In late 1954 at TRL, Trevor Wadley developed the Tellurometer as a portable device for measuring long distances easily and accurately. This was to revolutionise surveying practice and also inaugurated a major manufacturing industry in South Africa.
In April 1957 Wadley demonstrated the use of the Tellurometer in England on the Ridgeway Base and its extension. This was followed the next month by similar measurements on the Caithness Base in Scotland. Hölscher assisted him in both of these exercises. After his return to South Africa, Hölscher continued to develop the Tellurometer using higher radio frequencies in order to reduce errors in measured distances caused by radio waves reflected by ground. He also contributed by designing a solid-state version in which thermionic valves were replaced by transistors.
In 1964 Hölscher began a programme to develop an infrared version of the Tellurometer that would be used on the shorter distances required for cadastral purposes. Whereas the radio Tellurometer employed two manned devices to measure distance, Hölscher’s infra-red version needed only one, the remote station being replaced by a reflector designed to return the infrared waves along a path identical to the path taken by the incident ray. At a conference in Oxford in 1965 he had demonstrated that a Gallium Arsenide diode was an infrared source suitable for use in this application.
Dick Hölscher achieved an optical system founded on the Mangin Mirror, which is a design based on two spherical surfaces with a back surface reflection layer. His prototype achieved accuracies of 2 mm over distances of 1,5 km. See [2] for details. In 1964 he and his colleague Paul Cabion also worked together to modify the Tellurometer so that it complied with new specifications dictated by NATO.
The production model of the infrared version was developed and manufactured by Tellurometer (Pty) Ltd in Cape Town and named MA 100. Another version was manufactured and sold by Hewlett Packard as their HP3800A. These devices were the forerunners of many similar devices.
The University of Pretoria awarded him the degree DSc (Eng) in 1979. In 1980 the Suid Afrikaanse Akademie vir Wetenskap en Kuns awarded him its Gold Medal for excellence in fields of natural science.
In 1979 when a special commemorative stamp for the Tellurometer was printed in South Africa the CSIR made a presentation to Hewitt of a collection of photographs relating to that instrument. In 1994 Hewitt re-presented it "to my friend and former colleague Dick Hölscher whose contribution to the development of the Tellurometer in its later stages cannot be overestimated."
He retired from the CSIR in 1988 and until 2005 worked for the Institute for Marine Technology in Simonstown during which time he worked inter alia on various applications of sonar.
He was a devout, kindly and softly-spoken gentleman, endowed with an iron will that never accepted defeat or shoddy workmanship. He was an expert maker of stylish furniture. Though quiet and retiring he will always be remembered with affection by colleagues in the electronic surveying instrument field.
Acknowledgement
This article was originally published in the Survey Review and has been republished with permission.
References
- HD Hölscher: “The application of GaAs light emitting diodes to EDM equipment”, Symposium on Electromagnetic distance measurement, Oxford 1965, Hilger & Watts, pp. 436-447, 1967.
- HD Hölscher: “An electro-optical distance measuring system of high accuracy for short ranges”, Survey Review, 157. pp. 309-322, and 158. pp. 346-354, 1970.
Contact Jim Smith, Survey Review, jim@smith1780.freeserve.co.uk