TIDAL OBSERVATION METHODS
Faisal Widodo Bancin
Faculty of Earth Sciences and Technology, Institute of Technology, Bandung, Indonesia [email protected]
Tide is measured manually using tide pole or automatically using tide gauge (floating, acoustic and pressure), radar type, GPS Buoy, or altimetry satellite. The readings of tide pole might not as accurate as the reading of the automatic ones, thus what we record is a set of what we see. It might be subjects to observer’s capability to observe for a prolonged length of observation. The tide numbering might not be as précised as the automatic ones, so even if we points out the numbers correctly, the readings might still be wrong.
Floating type tide gauge compromise these conditions : both floater and weighter should be covered with a pipe, the pipe must be closed underneath to avoid strong waves and ripples, installed on a flat and stabile place and should be
protected from rains, winds, storm and waters. Since it depends on the floater to measure, any sudden significant mass bodies added to water nearby will create blob in water surface, thus resulting in error recording. Pressure type tide gauge system is based on the measurement of variability of mixed pressure measured of water and air. At times, for it also depends on angular force resulted from the weighter’s, the friction and energy loss or converted into friction are resulting to incorrect data recording. Any acoustic type is able to measure high frequency waves. It has 2 measurement methods, upper water and under water. Upper water type works by sensing the water surface without touching it. It is powered by solar panels. Data are transmitted to the control stations, and designed for permanent and long term water level measurements. The measurements are subjects to sun, therefore, whenever the light is out (the sun is blocked somehow), there can be no reading achieved. It is nearly useless in constantly clouded area. Under water type works by measuring the distance to water surface using SONAR principle. It is powered by dry cell batteries, thus no power and data cables needed. It is based on self-contained measurement and data logging.