Télémesure hydrologique par réseau téléphonique commuté

Hydrological telemeasurement using a public telephone system

¹ Professeur au Département de Génie Rural de l'Université Catholique de Louvain, Belgique
² Ingénieur Principal des Ponts et Chaussées, Chef de Service au Service d'Etudes Hydrologiques du Ministère des Travaux Publics, Belgique

Abstract

In Belgium, the public telephone system is used for transmission of analogical facts. This telemeasurement system, developped by the Agricultural Engineering Department of the Catholic University of Louvain, is presently operational in four administrations, among which the hydrological Study Service of the Ministry of Public Works. The system is composed of automatic receiving machines which, on receipt of a call, transmit on the telephone line analogical information (pure frequencies of 600-800 Hz) corresponding either to measurements at the time of the call or to measurements reflecting the history of a phenomenon (last 10 timed values). These receivers require no local power. At the call centre, a central set, managed by a microprocessor, enables calls to be sent out (automatically or manually); can receive and measure the analogical data received from the automatic receivers ; and process this data in order to transform it into directly useable values and transfer it all to a mass memory. The receivers are compatible with ail analogical or digital receivers. The information is returned to a precision of around 0.1 %. To date, 8 microprocessor calling sets and more than 200 field sets are in use on a permanent basis in Belgium. More specifically, the Hydrological Study Service has equipped its measurement network with 65 telelimnimetres and 15 pluviographs. Thanks to this network, the HSS was able to follow, in actual time, the exceptional increase in the level of the waters of the Meuse on 20th and 21st July 1980. The availability in real time of the level and rainfall measurements enabled the duty officer to foresee the evolution of the rising level and to take the necessary precautions. During this difficult and critical time, the percentage of accurate data received by the HSS was 92 % and this in spite of the fact that this was in the face of disaster.