What is Sounding in Hydrographic Surveying?
Sounding is an essential part of hydrographic surveying, which is the process of measuring the depth of a water body below the surface. This data is critical for making waterways navigable, as well as for understanding silting and scouring.
What is Hydrographic Surveying?
Hydrographic surveying is the science of measuring water bodies. It is used to accurately map out the depths and contours of rivers, lakes, and other aquatic environments. This data is then used to make waterways safer and easier to navigate, as well as to monitor water quality and to assess the impact of human activity on the environment.
Methods of Locating Soundings in Hydrographic Surveying
Methods of Locating Soundings
Conning the Survey Vessel:
Conning the survey vessel is one of the methods for locating soundings. This involves using visual observations from the boat to identify the depth of the water and any other features of the area being surveyed. The navigator must have a good understanding of the environment and be familiar with the navigational aids available in order to accurately locate soundings.
Observations with Theodolite or Sextant:
Observations with theodolite or sextant is another method for locating soundings. This involves using a theodolite or sextant to measure angles and distances from shore points to the survey vessel. These angles and distances are then used to calculate the position of the soundings. This method is often used in coastal areas where shore points are visible and accessible.
Theodolite Angles and EDM Distances from the Shore:
Theodolite angles and EDM distances from the shore is a third method for locating soundings. This involves using a theodolite to measure angles and EDM (electronic distance measurement) to measure the distance from shore points to the survey vessel. These angles and distances are then used to calculate the position of the soundings. This method is often used in areas where shore points are visible but not accessible.
Microwave Systems:
The fourth method for locating soundings is the use of microwave systems. This involves using radar or other microwave systems to measure the distance from the survey vessel to the soundings. The microwave systems can also be used to measure the angle of the soundings relative to the survey vessel. This method is often used in remote and inaccessible areas.
Sounding by Conning the Survey Vessel
Navigation Technique: Conning
Conning is a navigation technique used to keep a vessel or boat on a known course. This method is suitable for rivers, open sea up to 5 km off shore, and is divided into two sub-methods: Location by Cross Rope and Location by Range and Time Interval.
Location by Cross Rope
Location by Cross Rope is a navigation technique used to keep a vessel or boat on a known course. The technique involves using markers, known as ranges, which are fixed on the shore. The vessel or boat is navigated between the ranges.
Location by Range and Time Interval
Location by Range and Time Interval is another navigation technique used to keep a vessel or boat on a known course. This technique involves using markers, known as ranges, which are fixed on the shore. The vessel or boat is navigated between the ranges, and the time interval between each range is measured. This method is used to ensure the vessel or boat stays on its intended course.
Location by Cross Rope
What is Range-Ranging Method?
Range-ranging is a method used to measure the distance of a point from the shore. It is usually used in narrow channels or rivers and involves positioning a boat in range with two signals provided on the shore.
How Does Range-Ranging Method Work?
The boat is rowed at a constant speed and the time taken to reach the point of sounding is then measured. This allows the total distance of the point along the range to be determined.
Advantages and Disadvantages
The range-ranging method is more suitable for narrower channels and rivers. However, it is not as accurate as other methods.
Location by Range and Time Interval
METHOD OF RANGING
Ranging is a method of determining the distance of a boat from two signals, provided on the shore. This method is mostly used for channels or rivers with a smaller width and is not very accurate.
HOW TO PERFORM RANGING
To perform ranging, the boat is placed in a range between two signals on the shore. Then, the boat is rowed at a constant speed and the time taken for it to reach the sounding point is measured. This time measurement is used to calculate the total distance of the point along the range.
Sounding by Observations with Theodolite or Sextant
Measuring Angles in Surveying: Theodolite and Sextant
Theodolite and sextant are both instruments used to measure angles in surveying. There are several methods of locating soundings using these instruments, including:
Range and One Angle from the Shore:
This method involves using the range and one angle from the shore to locate the sounding. The range is the distance between the shore and the sounding and the angle is typically taken from the shore.
Range and One Angle from the Boat:
This method involves using the range and one angle from the boat to locate the sounding. The range is the distance between the boat and the sounding and the angle is typically taken from the boat.
Two Angles from Shore:
This method involves using two angles from the shore to locate the sounding. The angles are typically taken from the shore.
Two Angles from Boat:
This method involves using two angles from the boat to locate the sounding. The angles are typically taken from the boat.
One Angle from Shore and One Angle from Boat:
This method involves using one angle from the shore and one angle from the boat to locate the sounding. The angles are typically taken from both the shore and the boat.
Intersecting Angles:
This method involves intersecting two angles to locate the sounding. The angles are typically taken from both the shore and the boat.
Tachometric:
This method involves using a tachometric instrument to locate the sounding. The tachometric instrument measures the angle between two points, which can then be used to locate the sounding.
By Range and One Angle from the Shore
Introduction
The Range Line Method is a survey technique used to accurately plot the soundings of a boat in the water. This method involves two signals on the shore and the use of a theodolite or sextant to measure the angle of the soundings. The data collected is then used to determine the location of the soundings.
How Does the Range Line Method Work?
The Range Line Method works by keeping the boat in a range line with the help of two signals on the shore. The boat is moved and the point where the sounding is measured is observed by the theodolite or sextant, and the angle is noted. Using this angle, the point in the range can be fixed. Similarly, all other soundings are observed from different stations. For accurate results, the angle should be more than 30 degrees; otherwise, the fix will be poor. If the angle is less than 30 degrees, a new instrument station is selected.
Conclusion
The Range Line Method is an accurate and easy way to plot the soundings of a boat. This method involves the use of two signals on the shore and a theodolite or sextant to measure the angle of the soundings.
By Range and One Angle from the Boat
Angle Measurement From Boat
The angle measurement from a boat is a method of surveying that is used to locate points on the shore. This technique is highly accurate and involves taking angular measurements from the boat to various points on the shore. This method is suitable for surveying shorelines, inland waterways, ports, and other areas where the water depth is not too deep.
Angle Measurement From Shore
Another method of surveying is angle measurement from the shore. This method involves taking angular measurements from different stations located on the shore. The accuracy of this technique is similar to that of the boat angle measurement method. However, it has several advantages, such as better control for the surveyor and the ability to check the accuracy of the measurements by measuring a second angle towards a signal on the shore.
By Two Angles form the Shore
The Two Point Method for Water Sounding
The two-point method for water sounding is an efficient way to measure the depth of water bodies, especially when there are strong water currents making boating difficult. This method requires two instrument stations and two instrument men, set up at a distance from each other.
Angular Observations and Point Determination
From the two instrument stations, angular observations are done to determine the point where sounding is to be taken. If the angle created by the instruments is less than 300, a new instrument station is selected. This method eliminates the need for primary setting out and erecting range signals.
By One Angle from the Shore and One Angle from Boat
METHOD 1: ANGLE AND SOUNDING
This method uses two instruments and two people to measure the depth of a body of water. The first instrument is placed on the shore and measures the angle between the shore and the boat. The second instrument is placed in the boat and measures the angle between the boat and the second point on the shore. By taking both angles and the sounding from the boat, the depth of the body of water can be determined.
METHOD 2: ANGLE ONLY
This method also requires two instruments and two men to operate. Here, two instrument points are located on the shore, with only one instrument being placed at one point. The other instrument is placed in the boat, and the first angle is measured from the first point on the shore to the boat. From the boat, the second angle is then measured from the boat to the second point. At that instant, the sounding is also taken.
By Intersecting Angles
METHOD OF PERIODIC SOUNDING
Periodic sounding is a method used to determine the amount of sedimentation or erosion that has occurred in a harbor, reservoir, or other body of water. In this method, soundings are taken at the same points at regular intervals. A boat is rowed across the body of water, perpendicular to the shore, and soundings are taken at the point where an inclined line of signal flags intersects the line of the next signal flag. Flag rods are placed at the sounding points to avoid confusion for the next round of measurements. This method helps to monitor changes in the depth of the body of water over time.
By Tachometry
Method of Tachometer Measuring Distance
The tachometer measuring distance method involves placing a tachometer on the shore and positioning a staff on a boat. The tachometer can detect the staff’s “s” intercept, which is used to determine the distance between the boat and the instrument. This method is suitable when the water is still and the sounding location is close to the shore.
Sounding by Theodolite Angles and EDM Distances from Shore
Modern Method to Determine the Position of Sounding Vessel:
Electronic Distance Measurement (EDM) and Theodolite
The use of Electronic Distance Measurement (EDM) and Theodolite is a modern method used to determine the position of a sounding vessel. In this method, an EDM and a theodolite are placed in fixed positions on the shore. From there, a reflector placed on the boat is targeted and the point of sounding is located. This method is most accurate when the water is still and is one of the most reliable ways to fix the position of a sounding vessel.
Sounding by Microwave Systems
What is Tellurometer?
Tellurometer is a device used to measure the distance between a boat and two shore stations. It consists of three components: a master unit, a remote unit, and a master antenna. The master unit is fixed to the boat while the other two units are located at the two shore stations. The device uses microwaves to measure the distance and can be used for distances up to 100km from the shore.
How Tellurometer Works?
Tellurometer uses microwaves to measure the distances from the boat to the shore stations. The master antenna then produces two sets of range information based on the distances. With these two sets of range information, it is possible to accurately measure the distance between the boat and the shore stations.
