HOMS COMPONENT

TELEMETRY SYSTEM FOR DATA ACQUISITION AND FLOOD FORECASTING

1.   Purpose and objectives

     An automated water level and rainfall data collection system which can operate over existing VHF voice communication circuits, telephone or cell phone circuits and is a low cost alternative to satellite or dedicated radio network systems. Although the system provides essential data for 
flood forecasting, the primary purpose is to enable more efficient scheduling of hydrological field work.

2.   Description

     Currently the system works with three data logger types, Campbell, Unidata and Aquitel. It can accommodate other data logger types on request.

     The Aquitel system comprises five basic units:

     (a) A remote unit, installed at each field recorder, can accept signals 
         from two channels, typically a water level recorder (digital float
         type or pressure transducer), and a tipping bucket raingauge. The
         remote unit uses solid state memory to store up to approximately
         800 readings per channel (8 days at 15 minute intervals). The
         memory is maintained by an internal battery backup which preserves
         the data even if the main power supply (a lead acid battery
         recharged by a solar panel) fails.

     (b) A microbase unit, installed at each field centre, communicates by
         VHF radio with nominated remote units to extract stored data. It
         receives alarms from remote units and routes them to specified
         locations and equipment, carries out all telemetry housekeeping
         functions such as handling radio transmission protocols, battery
         voltage checking in remote units, error checking and correction,
         and communicates with the support unit. The microbase unit
         interfaces with a datalogger that holds the archive.

     (c) The support unit is easily carried by one man to remote units. It
         can be plugged directly into the remote unit to extract all the
         stored data should the radio circuit fail. These data are
         transferred when the support unit is plugged into the microbase.

     (d) The mobile unit is a portable unit operable from a vehicle or a
         home. It interrogates either the microbase or remote stations, to
         retrieve recent values. It also receives and issues alarms when
         the microbase is unattended.

     (e) Software resident in an accompanying microcomputer coupled to the
         microbase. This software, called FLOSYS, initialises the microbase
         and programs it to retrieve the specified data from remote units
         at predetermined times, or on demand.  The data are archived for
         further use and display using Tideda (Component G06.2.01).

3.   Input

     Signals on one or two channels at each remote unit from a water level recorder and/or a tipping bucket raingauge.

4.   Output

     Output includes records from remote stations for an office archive, and alarms if preset limits are exceeded.

5.   Operational requirements and restrictions

     (a) Each remote requires the erection of a pole for a radio aerial and
         a solar panel. Radio technicians are needed to check VHF radio
         transmission, and electronics staff to instal the telemetry unit.

     (b) Two weeks of training by a skilled professional is necessary
         before experienced field staff can operate this equipment.

     (c) Each water level recorder requires a remote unit, and a field party 
         operating several recorders requires a microbase unit at their
         office, a support unit, and (optionally) mobile units.

     (d) An existing VHF voice network can be used for radio transmission.

6.   Form of presentation

     Units with accompanying software and manuals (in English) for field and office installation.

7.   Operational experience

     The system has been operating throughout New Zealand since 1985, with 20 microbases and 200 Aquitel remotes in use in July 1999. Several hundred Campbell and Unidata logger sites are also operating. It has also been purchased for use for flood warning in Fiji.

8.   Originator and technical support

     National Institute of Water and Atmospheric Research Ltd, P.O. Box 8602, Christchurch, New Zealand

9.   Availability

     From the HOMS National Reference Centre for New Zealand.

10.  Conditions on use

     Available as a commercial package.

Last updated: 16 JULY 99)
 top