Professional Courses
Industry-relevant training in Business, Technology, and Design to help professionals and graduates upskill for real-world careers.
Categories
Interactive Games
Fun, engaging games to boost memory, math fluency, typing speed, and English skills—perfect for learners of all ages.
Typing
Memory
Math
English Adventures
Knowledge
Enroll to start learning
You’ve not yet enrolled in this course. Please enroll for free to listen to audio lessons, classroom podcasts and take practice test.
Interactive Audio Lesson
Listen to a student-teacher conversation explaining the topic in a relatable way.
Introduction to Magnetic Compasses
Unlock Audio Lesson
Today, we'll discuss magnetic compasses, a crucial tool in surveying. Can anyone tell me what a compass does?
A compass shows direction, right?
Exactly! It indicates the magnetic north. Now, can you think of why it's important in surveying?
It helps in measuring bearings to determine land boundaries.
Great point! We use compasses to measure angles and set up accurate survey lines. Let's dive into the types of compasses: prismatic compass, surveyor's compass, trough compass, and tubular compass.
Types of Magnetic Compasses
Unlock Audio Lesson
Let's explore the types of magnetic compasses. Who can describe the prismatic compass?
Isn't it the one with the sighting prism for better visibility?
That's correct! It provides a clear view of the graduated circle thanks to a prism. Can anyone explain the use of the surveyor's compass?
I think it has quadrantal graduations and doesn’t have a prism.
Exactly! It's simpler but less commonly used. Now, how about the trough and tubular compasses? What’s their function?
They’re used with other instruments, like theodolites, to help indicate the magnetic meridian?
Correct! They support the main instruments rather than being standalone.
Operational Principles of Magnetic Compasses
Unlock Audio Lesson
Let’s discuss how compasses work. Why does a magnetic needle point north?
Because of Earth's magnetic field!
Exactly! The needle aligns with the magnetic lines of force. How do we ensure accuracy in measurements?
By making sure the compass is level and correctly calibrated.
Right! And placing it on a stable base is key to avoiding errors in readings.
Does the compass ever get affected by nearby objects?
Yes! We must watch out for local attraction that may distort the readings.
Magnetic Bearings and Their Importance
Unlock Audio Lesson
Why do we care so much about magnetic bearings in surveying?
They help us understand the direction of survey lines!
Absolutely! Bearings allow us to determine the layout of land features accurately. Can anyone tell me what a fore bearing is?
It’s the bearing measured from the starting point to the destination.
Yes! And the back bearing is taken in the reverse direction. Why do we use both?
To check for consistency and accuracy?
Exactly! Comparing them helps to catch errors.
Introduction & Overview
Read a summary of the section's main ideas. Choose from Basic, Medium, or Detailed.
Quick Overview
Standard
The section introduces four main types of magnetic compasses employed in surveying: prismatic, surveyor's, trough, and tubular compasses. It elaborates on how these instruments work based on the concept of a freely suspended magnetic needle and the principles of magnetic bearings.
Detailed
Magnetic Compasses
In surveying, magnetic compasses are essential tools classified into four primary types: Prismatic Compass, Surveyor's Compass, Trough Compass, and Tubular Compass. These compasses rely on the principle that a magnetic needle, when freely suspended, aligns itself with the Earth’s magnetic field, providing a reference direction for surveying tasks. The prismatic compass is particularly popular due to its design that combines sighting and ease of reading, while the surveyor's compass is less common and features quadrantal graduations. The trough and tubular compasses are supportive instruments, used in conjunction with other surveying tools like theodolites, to ensure accurate alignment with the magnetic meridian. This section not only outlines the types of compasses but also emphasizes their operational principles and practical applications in obtaining magnetic bearings.
Audio Book
Dive deep into the subject with an immersive audiobook experience.
Types of Magnetic Compasses
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
The magnetic compasses used in surveying may be classified as:
1. Prismatic Compass
2. Surveyor's Compass
3. Trough Compass
4. Tubular Compass
Detailed Explanation
In surveying, there are several types of magnetic compasses that are commonly used. Each type serves specific purposes and has unique features. The main types include the Prismatic Compass, which is popular for various survey work, the Surveyor's Compass, which is less commonly used, and the Trough and Tubular Compasses, which are typically used as accessories with other surveying tools.
Examples & Analogies
Think of compasses as tools similar to different types of smartphones. Just as some phones are tailored for photography, while others are geared towards business productivity, each compass is designed for specific surveying tasks, whether it’s precise angle measurements or serving as an accessory to another instrument.
Working Principle of Magnetic Compasses
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
The compass works on the principle that a freely suspended magnetic needle takes the direction of the magnetic force at a place. It provides a reference direction with respect to which all angles can be measured.
Detailed Explanation
The fundamental principle behind a magnetic compass is based on magnetism. A magnetic needle, when suspended freely, will align itself with the Earth's magnetic field, pointing towards the magnetic north. This allows surveyors to establish a reference direction for measuring angles accurately. The north pole of the magnetic needle acts as the primary reference point in compass surveying.
Examples & Analogies
Imagine the magnetic needle of a compass is like a fish swimming in a river — it naturally aligns itself with the current (the Earth's magnetic field), which ensures that anytime you want to measure a direction (like taking a bearing), you can rely on that 'swim' direction of the needle.
Prismatic Compass Details
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
The Prismatic compass is very popular for survey work, and the Surveyor’s compass is rarely used. However, the principle of operation of both the compasses is the same, but they are made differently.
Detailed Explanation
The Prismatic compass is favored for its design and functionality in demonstrating the direction. It includes features like an eye vane for sighting, an object vane for aiming, and a graduated ring for taking precise readings. The Surveyor's compass, while less popular now, uses similar principles but differs in the absence of additional features like the prism that enhances visibility and precision of readings.
Examples & Analogies
Think of the Prismatic compass like a high-tech watch that not only tells time but also gives you health data and notifications. In contrast, the Surveyor's compass is like a classic watch that tells time but doesn’t have those extra smart features. Both tell time effectively, but one adds more convenience and accuracy.
Function of Trough and Tubular Compasses
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
Trough and tubular compasses are used as add-ons to other instruments. They are not complete surveying instruments by themselves but are used only to indicate magnetic meridian direction.
Detailed Explanation
Trough and tubular compasses serve as supplementary tools to other surveying instruments like theodolites or plane tables. Their role is to help indicate the magnetic meridian direction, allowing the primary instruments to be set accurately in the correct orientation. Thus, even though they are not standalone tools, they contribute significantly to the accuracy of measurements taken with larger devices.
Examples & Analogies
Consider a trough compass as a GPS app that you use alongside your paper map. The GPS helps you find the correct route (magnetic direction), but the paper map (main surveying instrument) provides the detailed layout of streets and landmarks. Both work together for effective navigation, just like the compasses assist other surveying tools in aligning the survey accurately.
Definitions & Key Concepts
Learn essential terms and foundational ideas that form the basis of the topic.
Key Concepts
-
Magnetic Compasses: Instruments that utilize a magnetic needle for finding directions.
-
Prismatic Compass: A popular surveying tool with a prism for ease of reading.
-
Local Attraction: Disturbance in reading caused by nearby magnetic materials.
Examples & Real-Life Applications
See how the concepts apply in real-world scenarios to understand their practical implications.
Examples
-
Using a prismatic compass to take bearings in a field survey.
-
Setting up a survey using a surveyor's compass for simpler measurements.
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
🎵 Rhymes Time
-
Compass, compass, point me right, guide my way both day and night.
📖 Fascinating Stories
-
A group of explorers ventures into the woods. They rely on their trusty prismatic compass, gleaming in the sunlight, helping them find their way home, illustrating how essential accurate bearings can be.
🧠 Other Memory Gems
-
Remember P for Prismatic, S for Surveyor, T for Trough, and T for Tubular for compass types.
🎯 Super Acronyms
PSTT - Prismatic, Surveyor, Trough, Tubular - types of magnetic compasses.
Flash Cards
Review key concepts with flashcards.
Glossary of Terms
Review the Definitions for terms.
-
Term: Magnetic Compass
Definition:
An instrument that shows direction relative to the Earth's magnetic field.
-
Term: Prismatic Compass
Definition:
A type of compass that uses a prism to view and read angles easily.
-
Term: Surveyor's Compass
Definition:
A simpler compass without a prism, often used for quadrantal measurement.
-
Term: Trough Compass
Definition:
An accessory compass used alongside other surveying instruments to indicate magnetic north.
-
Term: Tubular Compass
Definition:
A type of compass used with theodolites to assist in measuring angles.