Metode Pengamatan Pasut di (1)
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.
Water level observation uses local plane reference. Thus It makes any references acceptable. The simplest way possible
is by setting tide pole combined with automatic or manual data recorder since we can easily check the data by ourselves.
In coastal area, we need to determine whether the coastal area is homogenous or not. Therefore, it is important to locate
any nearby estuary. If there isn’t any, then it is validated to do measurement. In offshore areas where it is nearly
impossible to set tide pole, we use satellite buoy or LIDAR (satellite altimetry). In water level gauging system, the error
is considered to be mostly systematic. Therefore we need to make sure the gauge system is calibrated, so as to determine
systematic error within. From a set of data recorded, we need to manually compared them to the data resulted from
manual sounding (we can use either sounding pole or calibrated echo sounder).
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.
Water level observation uses local plane reference. Thus It makes any references acceptable. The simplest way possible
is by setting tide pole combined with automatic or manual data recorder since we can easily check the data by ourselves.
In coastal area, we need to determine whether the coastal area is homogenous or not. Therefore, it is important to locate
any nearby estuary. If there isn’t any, then it is validated to do measurement. In offshore areas where it is nearly
impossible to set tide pole, we use satellite buoy or LIDAR (satellite altimetry). In water level gauging system, the error
is considered to be mostly systematic. Therefore we need to make sure the gauge system is calibrated, so as to determine
systematic error within. From a set of data recorded, we need to manually compared them to the data resulted from
manual sounding (we can use either sounding pole or calibrated echo sounder).