RN-7 : Data collection and transmission system

Abstract

The report reviews the various systems of data collection and transmission in hydrology and hydrometeorology. Data on precipitation, evaporation temperature, humidity, wind velocity, sunshine hours, water level, discharge measurement, soil moisture etc. is required for use in weather and flood forecasting and efficient water management. Significant technological developments in the fields of telecommunication, computers and satellites are responsible for the automation of hydro meteorological observation techniques.

Various systems for collection of hydrometeorlogical data can be classified into three basic groups i.e. manual, semi-automatic (Man/machine mix) and automatic(computer controlled) observing station. In modern technology, point-to-point wireless communication ,manually operated systems are being replaced by modern systems like telemetry through VHF/UHF/micro-wave or satellite.

During recent years, the need for data has extended to inaccessible areas where up to now no information has been available. Insistence on high quality information as well as rapid receipt of data (for real-time analysis) has resulted in drastic changes both in the methods of collection as well as transmission of data. Data collection systems are of basically two types analog system and digital system. Analog systems encompass a wide hand-width of signal but have lower accuracy. Whereas digital systems are more accurate and are especially useful for multichannel recording systems. A variety of preliminary signal processing can also be performed on digital systems as the data is available in computer-compatible form. Some of the more commonly used hydrometeorological data transmitting systems are direct wire, telephone line, line-of-sight radio telemetry, radio relay, meteor-burst and satellite based system. The type of data transmission link to be used depends on the distances involved between measuring statibns and the receiving centre, and on the nature of the terrain. Depending upon the above requirements, various systems of data transmission have been recommended and their relative merits are outlined.

With the advent of microprocessors and micro-computers, data collection and transmission systems have undergone a remarkable improvement in terms of versatility and flexibility. Microprocessor-based systems are especially suitable for remote-field application which requires low-power, compact and flexible instrumentation. Flexibility is achieved by controlling the operations of the system through software.