Remote Sensing: towards the civil domain (1968 – 1970)

Remote Sensing towards the civil domain (1968 – 1970)

New insights

In the late 1960s, we began to realise that the problem of interpreting and using Remote Sensing images is deeper than just looking at pictures. Images are essentially the end results of an entire production chain. Understanding that chain allows one to optimise one’s system for specific tasks. Bandwidth was still a big problem at the time and digital techniques were not yet available. So one had to deal with your data stream economically. So the insight grew that we had to look at the beginning: the input, the recording itself. We started to develop so-called object-sensor studies. Equipment for this approach had now become available, such as measurement radars. in 1969 and 1970, we went up the TV towers again. This time to measure the radar reflectivity of crops [4]. This is where our collaboration with the CABO in Wageningen started, which would form the basis for the later Radar Research on VEgetation team (ROVE) team.

Q-band SLAR image of Zeeland; North and South Beveland at 500 ft (July 1964)
Q-band SLAR image of Zeeland; North and South Beveland at 500 ft (July 1964)
Wieringermeerpolder (juli 1964)
Wieringermeerpolder (juli 1964)
The IJssel east of Arnhem. River crossing of the A12 towards Germany. Traffic on the A12 is visible on the lower Moving Target Indicator (MTI) image (July 1964)
The IJssel east of Arnhem. River crossing of the A12 towards Germany. Traffic on the A12 is visible on the lower Moving Target Indicator (MTI) image (July 1964)

All this work led to all involved researchers, including both ANP project leaders, starting to wonder whether this new equipment could not also be made suitable for civil applications. At the beginning of 1968, this insight led to the declassification of a large part of their radar and infrared images recorded over the Netherlands by the English Defence. The RRE hoped that declassification (like TNO) could cultivate a wider interest in Remote Sensing. This change also made it possible to establish contacts with all kinds of official bodies. Therefore, the ITC could conduct a number of interviews with some of their official contacts in America at the Agricultural Research Service, NASA, Geological Survey, and the Department of the Interior. Those organisations were impressed by what had already been achieved in the Netherlands and in particular by the background research. In the US, there was well-developed Remote Sensing technology available but hardly any Remote Sensing physics. According to them, we were the only ones in Europe to work on these aspects. They also pointed to the commercial opportunities [5].

What do you do with such suggestions? It was decided to arouse interest among a wider circle of potential interested parties in the Netherlands.

Two X-band SLAR images of the Flevopolders from a great height (27,000 ft)  (June 13, 1968). The top image shows the SLAR looking to the south; on the bottom image the SLAR looks to the north. The strong north wind pushes long-spined crop towards the radar in the lower image causing more or less absorption of the radar waves. The top image shown how, flown to the north, the radar looks with the wind and thus more or less perpendicular to the stems, which produces a high echo.
Two X-band SLAR images of the Flevo polders from a great height (27,000 ft)  (June 13, 1968). The top image shows the SLAR looking to the south; on the bottom image the SLAR looks to the north. The strong north wind pushes long-spined crop towards the radar in the lower image causing more or less absorption of the radar waves. The top image shown how, flown to the north, the radar looks with the wind and thus more or less perpendicular to the stems, which produces a high echo.

From military to civilian applications

On June 25, 1968, a meeting was organised at the ITC to introduce the possibilities of the new sensors to the Dutch community or those potentially interested in aerial reconnaissance. Although some of the participants had heard of the new technology from literature, this presented information was completely new to most participants.

On September 4, 1968, a first meeting was held with representatives of Rijkswaterstaat. This resulted in agreements for SLAR flights in 1969. One of these flights, the observation of shipping on the North Sea in bad weather and poor visibility, was carried out in 1969 by Bomber Command (after direct contact was established between Rijkswaterstaat and the UK Ministry of Defence by the British ANP project leader). British ANP project leader later also made it possible for the Netherlands to borrow a prototype of the X-band SLAR for NIWARS (Dutch Interdepartmental Working Community for Application Research of Remote Sensing Techniques).

Prof. dr. C.J.F. Böttcher, the chairman of the Dutch Advisory Council for Government Policy said that the Council had just decided to set up an interdepartmental fund for joint research. He thought that an interdepartmental study into Remote Sensing could fit in well and suggested that the ITC (which came under Education and Science) and possibly Defence and Rijkswaterstaat be interested in this. This gave rise to the writing of two reports: one to the Director-General of Rijkswaterstaat [6] in which it was proposed to carry out further tests and one to the Minister of Education with a proposal for application research of modern aerial recording techniques [7].
In March 1969, the interdepartmental preparatory committee NIWARS was set up with the task of formulating a further proposal stating size required, costs, and duration. For example, NIWARS would become the first project to be financed from this policy area, in addition to a PTT project. As chairman, Prof. Eckhart managed to get the committee to finish its report fairly quickly: at the end of 1969 [8].
For the workers in the field, of course, everything went much too slowly. Fortunately, the work itself did not stand still. Also that year a scientific symposium was held, called “Aerial Observation with non-conventional systems” [9], organised by the Royal Institute of Engineers (KIVI) together with a number of more discipline-oriented sister associations. Here was reported on the experiments carried out in previous years, making them public. The symposium served its purpose by raising awareness of the possibilities of Remote Sensing. It provided background to the NIWARS Preparatory Committee.

That year, Rijkswaterstaat conducted a number of exploratory Remote Sensing experiments in the North Sea with the SLAR equipment from RRE and the infrared equipment from the TNO Physics Laboratory. This was the first time that the then still military and classified Remote Sensing equipment officially could be used for civil purposes in Europe.

These experiments included:

  1. Research into ship movements at sea, especially in bad weather and poor visibility,
  2. Capturing waves and swells, and locating oil spills.

 

X-band SLAR iamges of shipping on the Northe Sea (22 August 1969)
X-band SLAR iamges of shipping on the Northe Sea (22 August 1969)
Oil spill detection at sea with the TNO TIR scanner (1 July 1969)
Oil spill detection at sea with the TNO TIR scanner (1 July 1969)

One result of the experimental flights is worth mentioning separately. During a flight for Hoek van Holland, as the aircraft approached low tide, the bottom of the sea slowly appeared in the SLAR image. A completely unexpected and initially misunderstood effect: after all, radar cannot look into the water. Nevertheless, in collaboration with Rijkswaterstaat we soon succeeded in finding an explanation for the image. It was only when this phenomenon also appeared on radar images recorded by the SEASAT-satellite  in 1978 that this phenomenon became more popular and our explanation found confirmation and theoretical foundation [10]. In 1970 the report on these experiments was published for Rijkswaterstaat [11].

Q-band radar image of the sea bottom  topography near Rotterdam Europort, (19 Sept. 1969)
Q-band radar image of the sea bottom  topography near Rotterdam Europoort, (19 Sept. 1969)

In 1970, all these experiments led to the Director-General of the Directorate-General for Public Works and Water Management to order the manager of the Port Entrance Department to operationalise Remote Sensing techniques. The implementation was immediately taken in hand. Contracts were awarded to the TNO Physics Laboratory and the Dutch National Aerospace Laboratory. At first it was examined how the available observation equipment could be made flying. After all, the British (RRE) had made an X-band EMI SLAR available and the Royal Netherlands Air Force provided a thermal imaging scanner (made by Reconofax). After a thorough study and after it had become apparent that a separate aircraft for Remote Sensing was not feasible, the Remote Sensing equipment was built into the NLR’s laboratory aircraft. These actions made two observation systems available for conducting experiments for the applied research and for verifying the basic research.

Rijkswaterstaat continued to keep all work at sea in its own hands, even during the NIWARS period. This approach was initially viewed with dismay by some. In retrospect it turned out to be a blessing, because after the dissolution of NIWARS, Rijkswaterstaat guaranteed continuity in Remote Sensing projects through the Remote Sensing Guidance Committee until the arrival of the Remote Sensing Policy Committee (BCRS). The background investigation could also be continued.

Acknowledgment

Dr.Ir.G.P.de Loor gave a lecture on 7 June 1988 on the occasion of the 10th anniversary of the Circle for Remote Sensing on 17 August 2009. He wrote down the basis for this text. His lecture also appeared in an interim version in the Remote Sensing Newsletter no.95 of December 2000 at the closing of the NRSP.
 

References
  1. J.Ph. Poley: “Note on the resolution of radar systems”; Tijdschrift Nederlands Radiogenootschap, vol.22, 1957, pp. 187 – 194. 
  2. H.M. Oudshoorn: “The use of radar in hydrodynamic surveying”; Procs Seventh Conference on Coastal Engineering, edited by J.W. Johnson (The Hague: Council on Wave Research, The Engineering Foundation), 1960, pp. 59 – 76.
  3. G.P. de Loor, A.A. Jurriëns, W.J.M. Levelt and J.P. van de Geer: “Line-scan imagery interpretation”; Photogrammetric Engineering, vol.34, 1968, pp. 502 – 510.
  4. G.P. de Loor, A.A. Jurriëns and H. Gravesteijn: “The radar backscatter from selected agricultural crops”; IEEE Trans. Geoscience Electronics, vol. GE-12, 1974, pp. 70 – 77.
  5. G.P. de Loor, “Possibilities and uses of radar and thermal infrared systems”, Photogrammetria, vol.24, 1969, 43 – 48.
  6. RWS werkgroep, nota: “Radar en infra-rood luchtopnamen”, door Afd. Havenmonden bij brief nr. 128 dd. 10 jan. 1969 aangeboden aan de HID RWS in de Directie Benedenrivieren.
  7. ITC rapport: “Voorstel tot applikatie onderzoek van moderne lucht-opname technieken”, aangeboden aan de Minister van O en W, 10 jan. 1969.
  8. Interdepartementale Werkgroep Applikatie Onderzoek Moderne Luchtopname Technieken: “Concrete voorstellen voor het applicatie onderzoek van moderne luchtopname technieken”; Nota op 5 dec. 1969 uitgebracht aan de Minister van O en W, mede ten behoeve van zijn ambtgenoten.
  9. Verslag van het Symposium “Luchtwaarneming met niet-conventionele systemen”; De Ingenieur, vol.33, 1970, Afd. TWO nr.6 pp. o71 – o100 (6 artikelen, verslagen van het werk verricht van 1962 tot 1969).
  10. W. Alpers and I. Hennings: “A theory of the imaging mechanism of underwater bottom topography by real and synthetic aperture radar”; J. Geophys. Res., vol.89, 1984, pp. 10529 – 10546.
  11. Maritiem Geodetisch Bureau C. Don: “Proefopnamen met side looking airborne radar”; rapport samengesteld in opdracht van RWS, Directie Benedenrivieren, Afd. Havenmonden, Sectie Noordzee, 1970. Een herdruk verscheen in de RS Nieuwsbrief nr. 89, dec. 1999.
  12. “Verslag van een oriëntatiereis door de USA door een W.A.C.-delegatie in de periode van mei-juni 1971 in opdracht van de Stuurgroep van NIWARS”; ingediend door de voorzitter van de Stuurgroep op 15 nov. 1971.
  13.  N.J.J. Bunnik: “The multispectral reflectance of shortwave radiation by agricultural crops in relation with their morphological and optical properties”; Thesis Wageningen, 18 Jan 1978, also in: Comm. Agricultural university Wageningen, 78-1 (1978).
  14. G.P. de Loor, P. Hoogeboom and E.P.W. Attema: “The Dutch ROVE Program”; Trans. IEEE Geosci. and RS, vol.GE-20, 1982, pp. 3 – 11.
  15. Eindrapport NIWARS, rapport uitgebracht door de Stuurgroep van het beleidsruimte project NIWARS, 1 juni 1977.
  16. R.H.J. Morra: “Het begin van de remote sensing in Nederland”, 1958 – 1986”; publicatie van de Kring voor RS, maart 1990.
  17. L. Krul en G.P. de Loor: “Experiments with microwaves”; Int. J. Remote Sensing, 1992, vol. 13, nos. 6 and 7, 1201-1216.