Name: survey meridians for direction control
Uploaded: 2025-03-26T15:20:09.000Z
Duration: 1 min 28 s
Channel: JoVE

K12 Standards

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

9-12

Physical Geology

igneous-metamorphic-and-sedimentary-rocks

Igneous, Metamorphic And Sedimentary Rocks

Sedimentary

Meridians

In surveying, meridians serve as reference lines for measuring directions.&nbsp;A meridian is a fixed line running from the north to the south poles, and the four meridian types used in surveying are astronomic, magnetic, assumed, and grid.&nbsp;An astronomic meridian is aligned with the astronomic north, determined by the Earth's axis and gravitational forces.&nbsp;Observations of stars, like Polaris, help in its alignment. It is particularly useful for extensive land surveys, as its direction remains constant, enabling reestablishment in later years.On the other hand, the magnetic meridian is defined by a compass needle's orientation, affected by Earth's magnetic field. However, this meridian varies with location and time, reducing long-term accuracy.For smaller surveys, an assumed meridian is employed. This approach involves selecting an arbitrary direction, typically approximating astronomic north. While using an assumed meridian can simplify survey tasks, it has limitations. Specifically, if survey markers are lost, reestablishing the assumed meridian's direction becomes challenging.&nbsp;Additionally, a grid meridian, comprising a series of parallel meridians based on a central reference line, may sometimes be used to reduce complexity in local surveys.

meridians

In surveying, meridians are vital reference lines to measure directions and establish accurate land orientations. Meridians run from the north to the south poles, providing a stable framework for angular measurements and mapping. Meridians are fundamental in survey design, with the primary types being astronomic, magnetic, and assumed meridians. Each type offers distinct benefits and limitations, selected based on the project's scale and precision needs.The astronomic meridian is aligned with the astronomic north, defined by Earth's axis and gravitational forces. It is determined through celestial observations, often using Polaris, a fixed star near the north celestial pole. This meridian's reliance on a stable celestial reference allows it to maintain consistent orientation over long periods, making it particularly suitable for extensive surveys where long-term reestablishment of direction is necessary.&nbsp;In contrast, the magnetic meridian is established using a compass needle's alignment with Earth's magnetic field. The magnetic meridian's ease of use makes it easier to establish than the astronomic meridian. However, the magnitude and direction of Earth’s magnetic field depends where the measurement is taken, and also changes over time. As a result, it is not suitable for large or permanent surveys, as shifts in the magnetic field can affect the accuracy of measurements when referenced later.For smaller-scale projects, surveyors sometimes employ an assumed meridian, an arbitrary reference direction often approximating astronomic north. This approach simplifies surveys where high precision is less critical. However, if survey markers are lost, reestablishing an assumed meridian's direction can be challenging, as it needs an objective natural basis for realignment.Grid meridians may be used in certain cases, especially in rectangular coordinate grid surveying systems. A grid meridian consists of a set of parallel meridians based on a central reference line, reducing calculation complexity over smaller survey areas.

In surveying, meridians are vital reference lines to measure directions and establish accurate land orientations. Meridians run from the north to the ...

Education

JoVE Core

Civil Engineering

Unit 1

Angles and Directions

KEY TERMS AND CONCEPTS

survey meridians for direction control

Survey meridians are reference lines that help surveyors measure direction and set land orientation. They run from the north pole to the south pole and give surveys a stable frame for angular measurements and mapping. In survey design, meridians are chosen based on the size of the project and the level of precision needed.

An astronomic meridian is tied to astronomic north, which is based on Earth’s axis and gravity. Surveyors determine it through celestial observations, often by using Polaris, the fixed star near the north celestial pole. Because it relies on a steady sky reference, this meridian can keep its orientation for long periods and works well for large surveys that may need direction to be checked again later.

A magnetic meridian is set by a compass needle lining up with Earth’s magnetic field. It is easier to establish than an astronomic meridian, so it is useful when speed matters. However, Earth’s magnetic field changes by location and shifts over time, so magnetic meridians are not a good choice for large or permanent surveys.

For smaller projects, surveyors may use an assumed meridian. This is an arbitrary reference direction that often comes close to astronomic north. It can make surveying simpler when high precision is less important, but it can be hard to set again if markers are lost because it does not have a natural basis for realignment.

Grid meridians are another option in some survey systems, especially rectangular coordinate grid surveys. A grid meridian uses a set of parallel meridians based on a central reference line. This approach can reduce calculation complexity over smaller survey areas.

Survey Meridians for Direction Control

Survey meridians are reference lines that help surveyors measure direction and set land orientation. They run from the north pole to the south pole and give surveys a stable frame for angular measurements and mapping. In survey design, meridians are chosen based on the size of the project and the level of precision needed. An astronomic meridian is tied to astronomic north, which is based on Earth’s axis and gravity. Surveyors determine it through celestial observations, often by using...

azimuths and bearings

Survey Direction with Azimuths and Bearings

Azimuths and bearings are key ways to describe direction in surveying. They show the position of a line relative to a meridian, which is a reference north-south line. Surveyors use these measurements to communicate direction clearly and consistently. An azimuth is the clockwise angle measured from the north end of the reference meridian to the line being studied. It ranges from 0 to 360 degrees, so it gives a full-circle direction. This makes azimuth useful in navigation, cartography, and...

compass

Compass Bearings and Magnetic North

The compass is a navigation tool that uses Earth's magnetic field. Its magnetic needle lines up with magnetic north, which helps people find direction and stay oriented. Because magnetic north is not exactly the same as true north, a compass shows a slightly different direction than geographic north. That difference is called magnetic declination. Declination is the angle between magnetic north and true north, and it changes with location. It can also change over time because Earth's magnetic...

magnetic declination

Compass Error and Magnetic Declination

Magnetic declination is the angle between true north and magnetic north. True north points along Earth’s rotational axis. Magnetic north follows Earth’s magnetic field. Because the magnetic poles do not match the geographic poles, a compass does not point exactly toward true north. The size of magnetic declination depends on where an observer is located on Earth. It also changes over time because Earth’s magnetic field is dynamic. Declination is called eastern when magnetic north lies east of...

local attraction

Compass Errors from Nearby Magnetic Objects

Local attraction is a compass error caused by nearby magnetic influences. Metal fences, buried pipes, vehicles, buildings, power lines, and natural iron ore deposits can all disturb the compass. Small items such as wristwatches, steel tools, and belt buckles may also create local magnetic fields that bend the Earth's magnetic field and affect the reading. These disturbances make compass readings inaccurate. That can create problems in navigation and land surveying. Surveyors look for local...

design example: traverse angle computations

design-example-traverse-angle-computations

Closed Traverse Angle Checks

Closed traverse angle checks are used in surveying to calculate the internal angles inside a closed loop. A traverse is a set of connected lines that return to the starting point. Surveyors use it for land boundary mapping and other layout work. The process starts with known azimuths and bearings for the traverse sides. An azimuth is a direction measured from north, and a bearing shows the direction of a line in simple survey terms. Internal angles at each vertex are then found with basic...

key terms and concepts

Learn how astronomic, magnetic, assumed, and grid meridians help surveyors measure direction, set orientation, and choose the right reference line.

Survey Meridians for Direction Control | JoVE K12

JoVE Core Civil Engineering offers a foundational exploration of essential construction materials such as bricks, stones, steel, wood, and concrete, along with fluid mechanics topics like flow over immersed bodies, open channel flow, and dimensional modeling. It also covers key surveying concepts, including leveling, traverse adjustments, curve design, topographic mapping, and geospatial technologies (GPS & GIS). Science-in-action videos showcase laboratory research on materials, fluids, and surveying practices in real-world engineering systems.

civil engineering

Igneous Intrusive Rock

Source: Laboratory of Alan Lester - University of Colorado Boulder
Igneous rocks are products of the cooling and crystallization of high temperature ...

Igneous Volcanic Rock

Source: Laboratory of Alan Lester - University of Colorado Boulder
Igneous rocks are the products of cooling and crystallization of magma. Volcanic rocks ...

determining-spatial-orientation-rock-layers-with-brunton

Determining Spatial Orientation of Rock Layers with the Brunton Compass

Source: Laboratory of Alan Lester - University of Colorado Boulder
Most rock units exhibit some form of planar surfaces or linear features. Examples ...

using-topographic-maps-to-generate-topographic-profiles

Using Topographic Maps to Generate Topographic Profiles

Source: Laboratory of Alan Lester - University of Colorado Boulder
Topographic maps are &#34;plan-view&#34; representations of Earth&#39;s ...

Making a Geologic Cross Section

Source: Laboratory of Alan Lester - University of Colorado Boulder
Geologic maps were first made and utilized in Europe, in the mid-to-late 18th century. ...

Igneous
• Mafic and felsic rocks and minerals
• Intrusive (igneous structures: dikes, sills, batholiths, pegmatites)
• Earth's interior (inner core, outer core, lower mantle, upper mantle, Mohorovicic discontinuity, crust)
• Magnetic reversals and Earth's magnetic field
• Thermal energy within the Earth
• Extrusive (volcanic activity, volcanoes: cinder cones, composite, shield)
• Bowen's Reaction Series (continuous and discontinuous branches)

Content elaboration: This unit builds upon a variety of topics studied in middle school. In the Earth and Space Science strand, sedimentary, igneous and metamorphic rocks are introduced. Rocks and minerals are tested and classified. Plate tectonics, seismic waves and the structure of Earth are studied and the geologic record is introduced (including the evidence of climatic variances through Earth's history). In the Life Science strand, fossils and depositional environments are included as they relate to the documented history of life in the geologic record. In the Physical Science strand, waves, thermal energy, currents, pressure and gravity are presented. In this course, geologic, topographic, seismic and aerial maps are used to locate and recognize igneous, metamorphic and sedimentary structures and features. Technological advances permit the investigation of intrusive structures and the interior of Earth. Connections between the minerals present within each type of rock and the environment formed are important. The processes and environmental conditions that lead to fossil fuel formation (Note: this links to the energy resources section below) includes the fossil fuels found in Ohio, nationally and globally. Bowen's Reaction Series is used to develop an understanding of the relationship of cooling temperature, formation of specific igneous minerals and the resulting igneous environment. The focus is on knowing how to use Bowen's Reaction Series, not to memorize it. Virtual demonstrations and simulations of cooling magma and crystallization of the igneous minerals found on the series can be helpful in conceptualizing the chart. The magnetic properties of Earth are examined through the study of real data and evidence. The relationship of polar changes, magnetic striping, grid north, true north and the North Pole are included in the study of Earth's magnetic properties. Features found in the ocean include all types of environments (igneous, metamorphic or sedimentary). Using models (3-D or virtual) with real-time data to simulate waves, tides, currents, feature formation and changing sea levels to explore and investigate the ocean fully is recommended. Interpreting sections of the geologic record to determine sea level changes and depositional environments, including relative age, is also recommended. Technological advances can be used to observe and record the physical features of the Earth, including the ocean floor. Interpreting geologic history using maps of local cross-sections of bedrock can be related to the geologic history of Ohio, the United States and Earth.

Igneous

physical-properties-of-minerals-ii-polymineralic-analysis

Physical Properties Of Minerals II: Polymineralic Analysis

Source: Laboratory of Alan Lester - University of Colorado Boulder
The physical properties of minerals include various measurable and discernible ...

physical-properties-of-minerals-i-crystals-and-cleavage

Physical Properties Of Minerals I: Crystals and Cleavage

Source: Laboratory of Alan Lester - University of Colorado Boulder
The physical properties of minerals comprise various measurable and discernible ...

Metamorphic
• Pressure, stress, temperature and compressional forces
• Foliated (regional), non-foliated (contact)
• Parent rock and degrees of metamorphism
• Metamorphic zones (where metamorphic rocks are found)

Content elaboration: This unit builds upon a variety of topics studied in middle school. In the Earth and Space Science strand, sedimentary, igneous and metamorphic rocks are introduced. Rocks and minerals are tested and classified. Plate tectonics, seismic waves and the structure of Earth are studied and the geologic record is introduced (including the evidence of climatic variances through Earth's history). In the Life Science strand, fossils and depositional environments are included as they relate to the documented history of life in the geologic record. In the Physical Science strand, waves, thermal energy, currents, pressure and gravity are presented. In this course, geologic, topographic, seismic and aerial maps are used to locate and recognize igneous, metamorphic and sedimentary structures and features. Technological advances permit the investigation of intrusive structures and the interior of Earth. Connections between the minerals present within each type of rock and the environment formed are important. The processes and environmental conditions that lead to fossil fuel formation (Note: this links to the energy resources section below) includes the fossil fuels found in Ohio, nationally and globally. Bowen's Reaction Series is used to develop an understanding of the relationship of cooling temperature, formation of specific igneous minerals and the resulting igneous environment. The focus is on knowing how to use Bowen's Reaction Series, not to memorize it. Virtual demonstrations and simulations of cooling magma and crystallization of the igneous minerals found on the series can be helpful in conceptualizing the chart. The magnetic properties of Earth are examined through the study of real data and evidence. The relationship of polar changes, magnetic striping, grid north, true north and the North Pole are included in the study of Earth's magnetic properties. Features found in the ocean include all types of environments (igneous, metamorphic or sedimentary). Using models (3-D or virtual) with real-time data to simulate waves, tides, currents, feature formation and changing sea levels to explore and investigate the ocean fully is recommended. Interpreting sections of the geologic record to determine sea level changes and depositional environments, including relative age, is also recommended. Technological advances can be used to observe and record the physical features of the Earth, including the ocean floor. Interpreting geologic history using maps of local cross-sections of bedrock can be related to the geologic history of Ohio, the United States and Earth.

Metamorphic

Magnetism

Magnets are commonly found in everyday objects, such as toys, hangers, elevators, doorbells, and computer devices. Experimentation on these magnets shows ...

Magnetic Field Lines

The representation of magnetic fields by magnetic field lines is very useful in visualizing the strength and direction of the magnetic field. Each of the ...

Compass

The compass is a fundamental instrument that operates by aligning its magnetic needle with Earth's magnetic field. This alignment facilitates navigation ...

Magnetic Fields

Source: Yong P. Chen, PhD, Department of Physics &#38; Astronomy, College of Science, Purdue University, West Lafayette, IN
Magnetic fields can be ...

Sedimentary
• Division of sedimentary rocks and minerals (chemical, clastic/physical, organic)
• Depositional environments

Content elaboration: This unit builds upon a variety of topics studied in middle school. In the Earth and Space Science strand, sedimentary, igneous and metamorphic rocks are introduced. Rocks and minerals are tested and classified. Plate tectonics, seismic waves and the structure of Earth are studied and the geologic record is introduced (including the evidence of climatic variances through Earth's history). In the Life Science strand, fossils and depositional environments are included as they relate to the documented history of life in the geologic record. In the Physical Science strand, waves, thermal energy, currents, pressure and gravity are presented. In this course, geologic, topographic, seismic and aerial maps are used to locate and recognize igneous, metamorphic and sedimentary structures and features. Technological advances permit the investigation of intrusive structures and the interior of Earth. Connections between the minerals present within each type of rock and the environment formed are important. The processes and environmental conditions that lead to fossil fuel formation (Note: this links to the energy resources section below) includes the fossil fuels found in Ohio, nationally and globally. Bowen's Reaction Series is used to develop an understanding of the relationship of cooling temperature, formation of specific igneous minerals and the resulting igneous environment. The focus is on knowing how to use Bowen's Reaction Series, not to memorize it. Virtual demonstrations and simulations of cooling magma and crystallization of the igneous minerals found on the series can be helpful in conceptualizing the chart. The magnetic properties of Earth are examined through the study of real data and evidence. The relationship of polar changes, magnetic striping, grid north, true north and the North Pole are included in the study of Earth's magnetic properties. Features found in the ocean include all types of environments (igneous, metamorphic or sedimentary). Using models (3-D or virtual) with real-time data to simulate waves, tides, currents, feature formation and changing sea levels to explore and investigate the ocean fully is recommended. Interpreting sections of the geologic record to determine sea level changes and depositional environments, including relative age, is also recommended. Technological advances can be used to observe and record the physical features of the Earth, including the ocean floor. Interpreting geologic history using maps of local cross-sections of bedrock can be related to the geologic history of Ohio, the United States and Earth.

measuring-structure-composition-change-underwater-environments-with

Measuring the Structure, Composition, and Change of Underwater Environments with Large-area Imaging

Digital imaging and processing technology have evolved to facilitate the expansion of large-area imaging surveys, which increase our capacity to study the ...

a-field-primer-for-monitoring-benthic-ecosystems-using-structure-from

A Field Primer for Monitoring Benthic Ecosystems Using Structure-From-Motion Photogrammetry

Structure-from-motion (SfM) photogrammetry is a technique used to generate three-dimensional (3D) reconstructions from a sequence of two-dimensional (2D) ...

Thermal Expansion

The expansion of alcohol in a thermometer is one of many commonly encountered examples of thermal expansion, which is the change in size or volume of a ...

Density

Density is an important characteristic of substances, crucial in determining whether an object sinks or floats in a fluid. Its SI unit is kg/m3, and its ...

Tidal Forces

The origin of Earth&#39;s ocean tides has been a subject of continuous investigation for over 2000 years. However, the work of Newton is considered to be ...

The Water Cycle

The Earth&rsquo;s hydrosphere includes all of the areas where the storage and movement of water occurs. Since water is the basis of all living processes, ...

Climate Change

The certainty of climate change remains a public controversy despite the consensus among approximately 97% of active climate researchers, who not only ...

Gradually Varying Flow

Gradually varying flow (GVF) in open channels describes situations where water depth changes slowly along the channel due to factors like non-uniform bed ...

Streamlines, Streaklines, and Pathlines

Consider water flowing steadily through a curved pipe. The direction of flow inside the pipe can be visualized using streamlines.
A streamline represents ...

Hydraulic Jumps

Source: Alexander S Rattner and Mahdi Nabil; Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA
When ...

design-example-analyzing-capacity-contours-for-flood-risk-assessment

Design Example: Analyzing Capacity Contours for Flood Risk Assessment

Flood risk assessment involves careful planning and analysis to ensure the safety of communities near water retention structures. Capacity contours are a ...

Ocean
• Tides (daily, neap and spring)
• Currents (deep and shallow, rip and longshore)
• Thermal energy and water density
• Waves
• Ocean features (ridges, trenches, island systems, abyssal zone, shelves, slopes, reefs, island arcs)
• Passive and active continental margins
• Transgressing and regressing sea levels
• Streams (channels, streambeds, floodplains, cross-bedding, alluvial fans, deltas)

Content elaboration: This unit builds upon a variety of topics studied in middle school. In the Earth and Space Science strand, sedimentary, igneous and metamorphic rocks are introduced. Rocks and minerals are tested and classified. Plate tectonics, seismic waves and the structure of Earth are studied and the geologic record is introduced (including the evidence of climatic variances through Earth's history). In the Life Science strand, fossils and depositional environments are included as they relate to the documented history of life in the geologic record. In the Physical Science strand, waves, thermal energy, currents, pressure and gravity are presented. In this course, geologic, topographic, seismic and aerial maps are used to locate and recognize igneous, metamorphic and sedimentary structures and features. Technological advances permit the investigation of intrusive structures and the interior of Earth. Connections between the minerals present within each type of rock and the environment formed are important. The processes and environmental conditions that lead to fossil fuel formation (Note: this links to the energy resources section below) includes the fossil fuels found in Ohio, nationally and globally. Bowen's Reaction Series is used to develop an understanding of the relationship of cooling temperature, formation of specific igneous minerals and the resulting igneous environment. The focus is on knowing how to use Bowen's Reaction Series, not to memorize it. Virtual demonstrations and simulations of cooling magma and crystallization of the igneous minerals found on the series can be helpful in conceptualizing the chart. The magnetic properties of Earth are examined through the study of real data and evidence. The relationship of polar changes, magnetic striping, grid north, true north and the North Pole are included in the study of Earth's magnetic properties. Features found in the ocean include all types of environments (igneous, metamorphic or sedimentary). Using models (3-D or virtual) with real-time data to simulate waves, tides, currents, feature formation and changing sea levels to explore and investigate the ocean fully is recommended. Interpreting sections of the geologic record to determine sea level changes and depositional environments, including relative age, is also recommended. Technological advances can be used to observe and record the physical features of the Earth, including the ocean floor. Interpreting geologic history using maps of local cross-sections of bedrock can be related to the geologic history of Ohio, the United States and Earth.

Ocean

Survey Meridians for Direction Control

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