Name: compass bearings and magnetic north
Uploaded: 2025-03-26T15:20:13.000Z
Duration: 1 min 23 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

Compass

The compass, a vital direction-finding instrument, relies on Earth's magnetic field for its operation. Its needle aligns with magnetic north but deviates slightly from astronomic north, with the deviation varying by location.This deviation is called magnetic declination, influenced by Earth's magnetic field, which originates from currents in its liquid outer core. Declination changes over time and with location, necessitating adjustments for accurate readings.Historically, the compass was essential for navigation and surveying before advanced instruments like sextants and transits emerged.&nbsp;A surveyor's compass was commonly used to determine bearings by aligning its needle with magnetic north. Bearings were then read on a circular scale.The needle's sensitivity is critical, and it is ensured by minimizing wear on its pivot and counterbalancing its ends to prevent downward dips.&nbsp;Magnetic interference from nearby metal objects can distort readings, a challenge addressed by measuring bearings from multiple points.Though largely replaced by modern instruments, the compass remains a cornerstone in surveying history, illustrating the enduring significance of Earth's magnetic field.

compass

The compass is a fundamental instrument that operates by aligning its magnetic needle with Earth's magnetic field. This alignment facilitates navigation and orientation, offering a means to determine direction relative to magnetic north. However, the magnetic needle points to magnetic north, which differs slightly from true geographic north due to magnetic declination, which is the angular deviation between these two points. Declination varies based on geographic location and shifts over time due to the dynamic nature of Earth's magnetic field, which arises from convection currents in the liquid outer core.The compass was indispensable for navigation and surveying before advanced instruments such as sextants and transits were invented. Surveyors often relied on a specialized compass, the surveyor's compass, to measure bearings. This device operated by aligning the magnetic needle with the magnetic north, after which the bearing could be read on a graduated circular scale. Bearings obtained in this manner provided critical data for mapping and land division.The magnetic needle's sensitivity is essential for precise readings. To achieve this, the needle's pivot is carefully designed to minimize wear, while its ends are counterbalanced to prevent dipping due to Earth's magnetic inclination. Accurate readings also depend on avoiding interference from nearby metal objects, which can distort the magnetic field. Surveyors addressed this issue by measuring bearings from multiple points and averaging the results to account for anomalies.Although largely supplanted by modern electronic tools such as GPS and theodolites, the compass retains historical significance. Its reliance on Earth's magnetic field highlights the intricate relationship between natural geophysical phenomena and technological innovation.

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

Education

JoVE Core

Civil Engineering

Unit 1

Angles and Directions

KEY TERMS AND CONCEPTS

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 field is not fixed. The field comes from convection currents in the liquid outer core.

Before modern tools such as sextants and transits, the compass was essential for navigation and surveying. Surveyors often used a surveyor's compass to measure bearings. A bearing is a direction read from a graduated circular scale after the needle aligns with magnetic north. These measurements were important for mapping and dividing land.

Good compass readings depend on a sensitive magnetic needle. The needle's pivot is designed to reduce wear, and its ends are counterbalanced so the needle does not dip because of Earth's magnetic inclination. Nearby metal objects can disturb the magnetic field, so surveyors had to avoid interference. They also measured from multiple points and averaged the results to reduce errors from anomalies. Even though GPS and theodolites now do much of this work, the compass still shows how Earth's magnetic field supports practical technology.

Compass Bearings and Magnetic North

meridians

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...

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 a compass aligns with Earth's magnetic field, how declination affects north, and how surveyors used bearings for mapping and land division.

Compass Bearings and Magnetic North | 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 ...

Meridians

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

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.

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Compass Bearings and Magnetic North

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