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Geology
Identify five types of equipment used to determine tidal measurements.
A tide staff refers to a tide gauge that constitutes of a vertical staff from which a geologist can directly read the height of a tide. There are two types of tide staffs, a fixed staff and a portable staff. A fixed staff is one that cannot be easily removed and hence it is secured on one place. On the other hand, a portable staff can be removed from water when not in use.
Self recording tide gauges refers to an instrument that measures changes in sea level in relation to a datum. There are different types of tide gauges, such as: Kelvin type gauge, Fuess type gauge, Geographical Satellite Information (GSI) type gauge, High Accuracy Automatic Tide Gauge and High Resolution Automatic Tide Gauge.
RBRs loggers measure tides and waves. They measure the tide pressure. RBRs are accessible in various configurations such as: the RBR Virtuoso and the RBR Duo.
Radar Tide Gauge Recorder is an instrument that has the capacity to register an array of environmental factors of wind (direction and speed), space, temperature as well as humidity. The device can either be installed permanently for port businesses or can serve the function of a portable device.
A stilling well and float is a device designed in a manner that when hit by water waves, it stills the waters and only lets the energy possessed by the water waves to pass through it, thanks to its mechanical design. The filtered waves are then measured to determine scalar and vector quantities of the wave.
What are the features of potential sources of errors for the equipment?
The tide staff system cannot be transported from one place to another safely and without any trouble. It is therefore not suitable for making short-term tide measurements from one place to another. Besides, the tide staff system requires that a structure for erection of a tide-well and related components be constructed, prior to its installation. Furthermore, the tide staff system requires a long tube to guide the tide staff which is impossible in areas where the wind force keeps increasing.
Tide gauges face a number of difficulties in monitoring long term sea levels. Due to its features of internal memory, having a sensor, and dependence on power, it may experience technical problems. Some of these challenges include: tide gauge errors, datum errors, analysis errors as well as geophysical effects. Tide gauge errors include: technical issues like gauge setting and clock errors as well as accumulation of sediments in the stilling well. Datum errors may also arise as a result of anthropological related factors. If these errors are not corrected, they can completely invalidate the log of sea levels. Geophysical factors such as isostatic adjustments and tectonic movements affect the viability of results of the tidal gauges.
The utility of the RBR systems such as the surface recorder, the sea bed recorder and software are prone to failure. The failure of RBR software for instance, may lead to the storage as well as the transmission of inaccurate data to the geologists. Therefore it is advisable that this equipment be kept under constant maintenance to achieve the desired results. The RBR Virtuoso mainly runs on computerized systems which require electricity to run. In case of a power shortage, the RBR cannot register any tidal measurement necessitating the need for power backup.
The stilling well has a cylinder shaped cage installed within a tank to protect level instrumentation, like the displacer from fluid agitation which would lead to measurement error. It should be perorated so as to ensure the level of the stilling well is always uniform. There should be an adequate gap between the well and the displacer to avoid the liquid being clogged in between. The utility of Stilling well however does not guarantee 100% accuracy at all times. Failure of the mechanical system of the well may adversely affect the anticipated results. Conventionally, just like any other mechanical equipment, it is associated with mechanical breakdowns. The radar tide gauge recorder also experiences a similar problem. Besides, its utility may also be reduced if water clogs between the displacer and the stilling well. A good stilling well should therefore have a large aperture between the stilling well and the displacer.
What is the procedure to incorporate that information into the reductions of soundings, including connection to sounding datum?
Sounding datum refers to the depths recorded on nautical charts from selected sea and water levels. Generally, the reduction of sounding depends on the surface elevations as recorded in the gauge. It is quite a similar principle of determining a sounding datum. In this case however, transfer of water is dependent on a single reading at the ending of the line. It also does not benefit from the average of the previous readings. It is for this reason that in order to obtain accurate sounding reductions, the sounding region should be close to the control gauge. Determining the distance from the gauge beyond which this sounding should not be performed is difficult as the decision must consider factors of the needed survey accuracy, the slopes of the local surface which are affected by wind, river discharge and seiche among others. Sounding data is important on offshore gauging, non tidal waters as well as cotidal charts.
However, when the sounding datum cannot be obtained from the already existing bench marks (BMs), it may as well be determined by transfer of water from a location close to the gauge operation. The accuracy of this method depends on a set of heights which are obtained when the tide range is high. The gauge should be examined daily as this will be to ensure that no installations have been tampered with by the tides. For instance the gauge shelter, the staff gauge, the pressure sensor should all be inspected. The data is recorded in the comparison forms, leveling sheets as well as the gauge data forms for interpretation.
Works Cited
Hannah, John. An Updated Analysis of Long Term Sea Level Change in New Zealand. Geophys. Res. Letters. 2004.
Pugh, Danny. Changing Sea Levels, Effects of tide, Weather and Climate. Cambridge University Press. 2004.
