Bathymetric Lidar: Everything You Should Know About This Unique Technology

 

Bathymetric or topobathymetric lidar is the science of simultaneously recording and measuring three different surfaces: submerged land, land, and water. All the measurements and recordings are conducted through laser-based and airborne sensors.

This technology shares similarities with the terrestrial landscape's classic airborne lidar mapping technology. But there are also some differences between them.

The topobathymetric lidar sensors utilize two laser sources to obtain all the raw data, which is required to map out the three surfaces correctly. An infrared laser is utilized to map the water surface and the land. This particular light is reflected and absorbed by the water.

Doing so offers a proper representation of the shape and location of the water surface effectively. There are many other things to learn about this technology. Let’s find out from this article.

The Components of Bathymetric Lidar

The bathymetric lidar uses an infrared wavelength of 532nm to pierce through the water column and measure the sea floor. Besides that, the technology comes with sensors that are simplified in the form of 4 main components, and they are:

·      The GPS receiver provides the aircraft with the proper position. Sensors that can read all the returning signals

·      The IMU or inertial measurement unit gives the yaw, roll, and pitch of the aircraft

·      Laser scanner that emits the signal within a specific pattern

Knowing the orientation and position of all these elements will allow the lidar system to record accurate measurements. Many of these sensors can also measure over 100,000 points every second, which results in surveys with highly accurate data.

A survey delivered for Samoa showed that more than 1.8 billion points were captured within 1100km. But the deepest of these measurements was able to gain a depth of more than 75m.

The Environmental Deliberations

Addition of water columns in the lidar surveys makes them much more vulnerable than their topography. This can hurt the environment. Moreover, these impacts will lead to a lessening of measurement quality, data gaps, and the reduction of data coverage.

So, the best way to lessen these impacts and obtain a proper bathymetric lidar survey is by considering several factors. These factors are:

·      Sea condition

·      Air traffic controls

·      Tides

·      Weather for flying

·      Ground control accessibility

·      Turbidity

·      Vegetative condition

The lack of water clarity is a massive hindrance to the shallow-water penetration from this technology’s sensors. Low-reflectance seafloors, high-level of turbidity, and sea grass increases pose a risk to the success of a particular survey. Managing and understanding all these conditions can provide a proper meaning to the difference between failure and success.

The Characteristics of the Bathymetric Lidar Sensors

The sensors of the bathymetric lidar have different characteristics when compared with the sensors of the topographic lidar. Besides that, all the modern bathymetric lidar sensors can also easily measure the topography.

The major division is between the deep-water systems [>10m] and the shallow-water systems [<10m]. Shallow water systems contain:

·      The low laser power per pulse

·      Measures water depths in the visible water column

·      It has a higher measurement frequency

·      Small receiver field of view

·      Small laser footprint diameter

The marine bathymetric lidar systems, on the other hand, utilize:

·      More power per pulse

·      Lesser measurement frequency

·      Receiver field of view

·      Larger laser footprint

These deep-water systems differ significantly in the depth-penetration capacity between 2.0 and 3.0 times the Secchi-depth measurement. To maximize the coverage and detail greatly, the bathymetry survey operators use deep and shallow water sensors simultaneously to twin the optical port survey aircraft.

What are the Applications of Bathymetric Lidar?

The bathymetric lidar carries many crucial applications, and some of these are:

·      Coastal zone management

·      Coastal and Shoreline intelligence

·      Floodplain modeling

·      Habitat restoration

·      Infrastructure engineering and planning

·      Volumetric analysis

As a survey operator, if you learn how to use these applications properly, it will increase your knowledge of the nearshore setting so that you can improve:

·      Nautical charting

·      Marine debris mapping

·      Shoreline delineation

·      Benthic habitat mapping

·      Marine resource mapping

What Can Bathymetric Lidar Do?

Bathymetric lidar can provide you the power to seamlessly map the:

·      Stream channel

·      Morphology

·      Habitat connectivity

·      Floodplain topography

·      Unprecedented detail

·      Riparian vegetation

This particular technology has advanced the ability to map dynamic floodplains comprehensively and guide inundation modeling and canal and dam infrastructure evaluations. It will also allow you to effectively guide the watershed and river restoration efforts. The mapping can provide you with crucial baseline information that will support the planning and engineering of the dam removal projects. The data will also help with the rail and road crossings and telecom and pipeline infrastructure.

Ending Note

When employing and opting for the bathymetric lidar sensors, you must consider the crucial environmental factors and the separate characteristics of the system. The success of the survey will be determined by the experience and knowledge of the operator. Companies such as the NV5 offer excellent service when it comes to bathymetric lidar surveys. You will get accurate data, and it’s guaranteed that the surveying will be done within a given timeframe.