Understanding Leveling Terms for Surveying
Leveling is an essential surveying technique which is used to measure the elevation difference between two points. To find the elevation difference, the elevation of at least one point must be known. But what if the elevation of the points is unknown? Understanding the basic terms of leveling is the key to being able to survey with unknown elevation points.
Understanding the Basic Terminology of Leveling
Leveling is a surveying technique used to measure the elevation difference between two points. To calculate the elevation difference, the elevation of one or more points must be known. However, if the elevation of the points is not known, it can still be possible to conduct the survey with a basic understanding of the terminology used in leveling.
Terms Used in Leveling
Vertical Line
What is a Vertical Line in Leveling?
A vertical line in leveling is a line that runs perpendicular to the horizontal plane. It is used to measure elevations and differences in height between two points. It is also used to measure the slope of a hill or other topographical features.
Horizontal Line
What is a Horizontal Line in Leveling?
A horizontal line in leveling is a line that is parallel to the horizontal plane. It is used to measure the elevation of points on the ground, or the difference in elevation between two points. It is also used to measure the contours of a hill or other topographical features.
Level Surface
What is a Level Surface in Leveling?
A level surface in leveling is a surface that is flat and level. It is used to measure the elevation of points on the ground, or the difference in elevation between two points. It is also used to measure the slope of a hill or other topographical features.
Datum
What is a Datum in Leveling?
A datum in leveling is a reference point from which all other measurements are taken. It is used as a point of reference for measuring the elevation of points on the ground, or the difference in elevation between two points. It is also used to measure the contours of a hill or other topographical features.
Benchmark
What is a Benchmark in Leveling?
A benchmark in leveling is a marker or point that is used as a reference for measuring elevations or differences in elevation. It is used to measure the elevation of points on the ground, or the difference in elevation between two points. It is also used to measure the slope of a hill or other topographical features.
Mean Sea Level
What is Mean Sea Level in Leveling?
Mean sea level in leveling is a reference point from which all other measurements are taken. It is the average height of the oceans over a certain period of time and is used as a reference point for measuring the elevation of points on the ground, or the difference in elevation between two points.
Reduced Level
What is a Reduced Level in Leveling?
A reduced level in leveling is the elevation of a point on the ground in relation to the datum. It is the difference between the elevation of the point on the ground and the datum, and is used to measure the elevation of points on the ground, or the difference in elevation between two points.
Vertical Line
WHAT IS PLUMB LINE?
A plumb line is a line that is vertically aligned with the center of the earth. It is indicated by a plumb at the required station and is used to measure the verticality of a structure. The instrument is set up at the station with its center being the point where the plumb is released from the instrument height with the help of a thread.
HOW DOES A PLUMB LINE WORK?
A plumb line works by connecting the station point to the center of the earth. The instrument is set up at the station, and a plumb is released from the instrument’s height with the help of a thread. The vertical line from the station point to the center of the earth is the plumb line. This line is used to measure the verticality of a structure.
WHAT IS THE PURPOSE OF A PLUMB LINE?
The purpose of a plumb line is to measure the verticality of a structure. By connecting the station point to the center of the earth, the plumb line can be used to determine the verticality of a structure. This is important in order to ensure the structural integrity of any building or construction.
Horizontal Line
What is Horizontal Line?
A horizontal line is a line of sight of an instrument which is tangential to a level surface, and is perpendicular to the plumb line. In other words, it is a line which is aligned with the horizon.
Horizontal Surface
The surface along the horizontal line of sight is referred to as a horizontal surface. This surface is used to measure the elevation of a point with respect to the sea level. It is also used to measure the difference in elevation between two points.
Level Surface
What is Level Surface?
Level surface is a continuous surface which is parallel to the mean spheroid of the earth. A line representing the level surface is known as a level line which makes right angles to the vertical line or plumb line at any point. As it is a curved surface, it is considered as a plane surface for smaller area works.
Definition of Level Line
Level line is a line which is used to represent the level surface. It is a line that makes right angles to the vertical line or plumb line at any point which means that any point on the level line is equidistance from the center of the earth.
Datum
What is a Datum Line?
A datum line is a reference line used to establish the levels of other station points. It is an important element of surveying and is used to measure vertical distances, calculate elevations, and compare heights of various points. The datum line is typically established by an instrument such as a spirit level, which is set at a known elevation. All other station points are then measured with respect to this reference line.
Mean Sea Level
What is Mean Sea Level?
Mean sea level (MSL) is the average height of the ocean’s surface, which is determined by taking the mean of all the high and low tides recorded over a 19-year period. It is used as a reference point in surveys and other observations in a particular region.
Why is Mean Sea Level Used?
Mean sea level is used as a datum level for surveys and other observations in a particular region. This serves as a reference point that allows for the accurate measurement of changes in the sea level over time. It also provides a consistent baseline for the comparison of sea levels in different regions.
Reduced Level
What is Reduced Level?
Reduced Level is the height difference between a given point and the datum line or the mean sea level. It is a measure of the height of the point above or below the datum line and is used in surveying applications. Reduced Level is also referred to as Reduced Level of a point or Reduced Level of a survey point.
Benchmark
What is a Benchmark?
A benchmark is a point in a survey with a known elevation that is either above or below the datum line. It is used as a reference point to check the elevation of other points in the survey.
Types of Benchmarks
There are several types of benchmarks used in surveying. These include:
Great Trigonometrical Survey Benchmarks:
Great Trigonometrical Survey (GTS) benchmarks are used in the GTS survey, which is a system of triangles that form a network of survey points across India and Burma. These benchmarks are used to measure the height of mountains and other landforms.
Permanent Benchmarks:
Permanent benchmarks are markers that are set in place and remain at a fixed elevation. These are used to measure elevation changes over time.
Temporary Benchmarks:
Temporary benchmarks are markers that are set for a specific period of time and then removed. These are often used for short-term surveys.
Arbitrary Benchmarks:
Arbitrary benchmarks are markers that are set at an arbitrary elevation. These are used when the exact elevation is unknown or when the elevation is not important.
Great Trigonometrical Survey Benchmarks
What is a Great Trigonometrical Bench Mark?
Great trigonometrical bench marks (GTS benchmarks) are very precise points of reference established by survey authorities of a given country. These points are determined by taking the mean sea level as the datum. GTS benchmarks are marked with a concrete pedestal, topped with a bronze plate with the benchmark’s value inscribed on it. This pedestal is usually protected by a masonry structure built around it.
Establishing GTS Benchmarks
GTS benchmarks are established by conducting high precision surveys. These surveys are conducted by the survey authorities of the respective countries. The bronze plate located on the concrete pedestal of the benchmark contains the information and the value of the benchmark.
GTS Benchmark Agencies
Various agencies are responsible for establishing GTS benchmarks in different countries. Some of the agencies include the United States Geological Survey, the United Kingdom Ordnance Survey, and the Australian Government Geoscience Australia.
| Country | Agency / Authority |
| India | Survey of India |
| United Kingdom | Ordnance survey |
| United states | The national Geodetic surveyThe United States Army Corps of EngineersThe United States Forest ServiceThe United States Geological Survey |
| Japan | Geographical Survey institute |
| Canada | Natural Resources Canada |
| New Zealand | Land Information New Zealand |
| Pakistan | Survey of Pakistan |
Permanent Benchmarks
What are Permanent Benchmarks?
Permanent benchmarks are markers set with reference to the Ground Truth Surveying (GTS) benchmarks. They are usually established by local state government agencies or railways, and can be found at railway stations, public buildings and bridges. These benchmarks are used for future reference and can provide useful information when surveying.
Where Can Permanent Benchmarks Be Found?
Permanent benchmarks are typically found in railway stations, public buildings and bridges, as they are set by government agencies or railways. They are also used to help surveying, as they can provide useful information when conducting surveys.
What is the Purpose of Permanent Benchmarks?
The purpose of permanent benchmarks is to provide a reference point for future surveying. They are established with reference to GTS benchmarks, meaning that they are reliable markers that can be used to provide accurate information when conducting surveys. They are also useful for future references, as they can provide a reliable point of reference for future surveying.
Temporary Benchmarks
What are Temporary Benchmarks?
Temporary benchmarks are points or objects used by surveyors in the field to mark the position up to which a survey is completed. These points are established to make it easy to resume the survey from the same point after a long gap or the next working day.
How are Temporary Benchmarks Established?
When establishing temporary benchmarks, it is important to ensure that the point or object is permanently fixed in that position. This ensures that the survey can be resumed from the exact same point in the future.
Arbitrary Benchmarks
Elevation Difference in Small Surveys
When conducting small-scale surveys or engineering projects, it is important to know the difference in elevation between two points. However, it is not possible to accurately determine the reduced level of a certain area with respect to mean sea level. As a result, some fixed points in that area are taken as bench marks and given arbitrary values, such as 50 m, 100 m, 200 m, etc.