The term bathymetric is derived from two Greek words (bathus) which means deep and (metron) meaning measure. Therefore, bathymetric Lidar is studying the underwater depth of large water masses such as the floors of oceans and lakes. Before the invention of the new technology of studying large water masses’ floors, this practice was done through other measures. Such measures involved; use of a pre-measured heavy rope or any other material similar to a rope. The material used could be lowered from the side of the ship; however, due to this method’s inefficiency and inaccuracy, there was a need to devise alternative means.
How is Bathymetric Lidar Done Today?
Today the data relied on making bathymetric maps is obtained from sonar which is fixed beneath or even over the side of a water vessel such as a boat. The information about the depth of the sea, ocean, or even the lake is determined by the time taken by the beam of sound to travel downward to the floor of the sea or from the Ladar systems. The time taken by the light or sound for that matter to move through the water, bounce off the seafloor as well as get back to the sounder determines the distance to the floor of the sea, ocean, or any other big water mass.
A peek at bathymetric history
By the 1930s, bathymetric maps were made by single beam sounders. Today’s tech has led to much advancement in this field, and the experts use multi-beam echo sounders. This technology uses multiple narrow adjacent beams which are arranged in a structure that resembles a fan swath. These beams are packed tightly in an array of narrow individual beams to provide a great angular resolution as well as accuracy. It is evident that a depth-dependent wide swath allows a boat to map many seafloors within a short period compared to a single beam echosounder by making fewer passes.
The beams can update multiple times within a second; it is estimated that they can do 0.1 to 50 Hz within one second depending on the depth of the water body being worked on. This is in respect to boat speed while is a hundred percent coverage of the seafloor.
Altitude sensors
There are altitude sensors that provide correction for the vessel’s roll and pitch on the surface of the water body. A gyrocompass is essential in this field as it gives accurate heading data to correct for boat yaw. Many modern multibeam echo sounders systems are provided with an integrated motion-sensor and position system for checking yaw and any other dynamics or position to keep the safe vessel while on large water masses.
For instance, a boat fixed with GPS (Global Positioning System) or GNSS (Global Navigation Satellite System) will position the soundings according to the earth’s surface. The speed of sound profiles the sound speed in water as a function of the deepness of the water column precise for ray bending of the waves of sound which owes to the non-uniform water column features such as pressure, temperature as well as conductivity.
The system of the computer will process all the data while at the same time making all the necessary corrections for factors such as temperature, conductivity, and pressure. The results obtained from the measurements of the sound are processed. The processing can be done automatically, semi-automatically, or even manually to map the required region.
The Uses of Bathymetric Lidar.
Bathymetric Lidar has various uses, here are a number of them:
It is used for archaeological research as well as historical landscapes study.
This involves the use of remote sensing tech. The use of Bathymetric Lidar in these fields has led to revolutionizing of archaeology. Light detection and ranging (LiDAR), a remote sensing technology, involves the use of lasers as topographic scanners capable of penetrating foliage has attracted researchers in landscape archaeology commonly known as the field of settlement. This technology gives detailed data on the landscape for vast spatial areas while at the same time permitting visualization of the same landscapes in ways that have been impractical there before. Both the visualizations and the data have been used to understand better historical landscapes and how they were used in the past by older people.
Bathymetric Lidar is used for remote sensing of coastlines:
Monitoring, detection, and detection. This practice applies to the United States of America system, although it can be practiced similarly in all other parts of the world. For instance, visual interpretation of airborne remote sensing data is famous and widely practiced for coastal demarcation. There are various techniques and remote sensing data available for monitoring, extracting, and detecting coastal lines.
Bathymetric Lidar is used in Exploration of Spatiotemporal Trends in Commercial Fishing.
Fishing is a food generating activity and a key source of income among diverse world populace, therefore making it essential to maintain it since it is a scarce resource. Bathymetrical Lidar is applied in giving information about the spatial as well as the temporal footprint of fisheries. In a wide range of fishing activities, this technique is used in the monitoring of fishing vessels. This is important in assessing fishing activity to provide information to the marine spatial for proper planning.
- Breaking wave measurement.
This is another field in which bathymetrical Lidar is applied. Activities such as beach erosion as well as bedform are believed to occur as a result of the energetic breaking of waves. It can also be caused by other physical forces such as currents, tides, winds, river runoffs, among others. The profile shape formation in the beaches develops while responding to breaking waves. The monitoring of the beach is done by the use of LIDAR (3-D laser scanners). The Terrestrial LIDAR is also capable of detecting the beam signals reflected by the broken and the breaking waves within the shore.
Bathymetrical LIDAR is used in watershed width function estimation.
The hydrologic response of watersheds influences channel network and terrain changeability. This response is represented by the width function according to idealized flow settings of constant rate and lack of losses. The use of landscape data can project this situation. This study addresses these matters in this way:
- Illustrate the utility of useful statistical approximation of geomorphic tasks and metrics. This provides data decrease, and it can be projected to significant landscape datasets.
- Grow a framework for the approximation of breadth purposes. This is attained by using a mixture of truncated skew-usual distributions that take a wide variety of distribution forms.
- Demonstrate a functional approximation approach’s function by categorizing hydrologically similar watersheds founded on deviation measures applied to the breadth function estimations.
- Offers a basis for typical selection founded on the Bayesian Information Criterion.
- This technology is used in mapping the depth of water bodies. To achieve this, the green light sensor is used. The green light sensor can penetrate the surface of the waters to get to the exciting water regions. The challenging bit of this tech is that the water conditions interfere with the penetration of green laser. Some of the factors that limit the ability of green laser penetration include; water waves commonly known as turbidity, the vegetation found in water, the clarity of the water, among other factors. These factors are commonly experienced in shallow inland waters.
- This technology has made monitoring water depths easy and effective. It is also a cost-effective method compared to manual GPS measurements.
- Bathymetric Lidar is used in monitoring the level of water in turbid reservoirs. Monitoring the water level in reservoirs characterized by slopping banks in water bodies such as earth –dam and lakes has been challenging, mostly when done using airborne or terrestrial techniques.
- However, this undertaking has been made easy by using Bathymetric LiDAR tech, which employs the use of terrestrial near-infrared Lidar fixed with a large incidence angle. The required angle should at least range between forty and seventy degrees. The experts who employ this technology assume that Lidar can detect the subsurface and the surface of the water body so long as it has enough suspended particles.
- The suspended particles aids in backscattering the light which is emitted by the instrument to its detector. The tests conducted using commercial Lidar have proved that this technology can be applied to estimate the water level in reservoirs with a moderate accuracy of positive or negative 0.05, which is equivalent to (p=0.95). This applies to conditions where water turbid. The experts in this field have suggested the possibility of an enormous improvement of the versatility as well as the accuracy of this tech.
- This technique is also used in the monitoring and mapping of landslides. The main models of Lidar applied in mapping as well as monitoring of landslides are mobile and static devices. The mobile device used in this field is categorized according to the platform configuration. The static ones are commonly named ground-based LIDAR or terrestrial laser scanners.
Conclusion.
Bathymetric Lidar has proved to be of great importance in studying the floors of large water masses as well as conducting other adventures. This technology has helped man to perform great studies on areas where no one would have imagined whether their study can be attained.
