Loading the lesson
Loading the lesson
Search AllRounder.ai
Search the courses, subjects, tracks, games and features, or jump straight to a page.
Search the courses, subjects, tracks, games and features, or jump straight to a page.
Learn it your way
A short class with Sarah and her students. The other ways are under More.
Sign up free to listen. Transcripts are free to read.
Today, we are diving into the concept of bearings in surveying. Who can tell me what a bearing is?
Isn't it just the direction of one point to another?
Exactly! Bearings indicate the direction of a survey line with respect to a reference meridian. Now, can anyone tell me the types of meridians we use?
There are true meridian and magnetic meridian, right?
That's correct! The true meridian is established through astronomical observations while the magnetic meridian relates to where a magnetic needle points. This is key in obtaining accurate measurements. We can use a mnemonic like 'T for True, M for Magnetic' to remember these.
That's helpful! So, how do we actually measure these bearings?
Great question! Bearings can be measured either as Whole Circle Bearings or Reduced Bearings. Let's focus on Whole Circle Bearings first.
Whole Circle Bearings (WCB) are measured clockwise from north. Can someone tell me its range?
0 to 360 degrees!
That's right! Now, about Reduced Bearings. Does anyone know how they are measured?
They are measured from the north or south towards the east or west, and can never exceed 90 degrees.
Exactly! We use letters N and S for north and south, and E and W for east and west. For instance, we might write a bearing as N30°15'E. Can we think of an acronym to help us remember how to notate Reduced Bearings?
How about 'NSEW' for North, South, East, West?
Perfect! It’s essential to understand these classifications in order to accurately communicate directions during surveys.
Moving on to measurement tools, what kind of compasses are used in surveying?
I believe there are prismatic compasses and surveyor’s compasses?
Correct! The prismatic compass is popular for portability and ease. Can anyone tell me how its design helps in measuring bearings?
It has a prism that allows you to see the reading on the graduated ring while sighting a target.
Exactly! This design minimizes parallax errors. Remember, good technique is vital for accurate measurements. Can anyone provide a memory aid for using a compass?
How about 'Level, Align, Read' as a step reminder?
Great mnemonic! Keep practicing that, as precise usage will improve your surveying skills!
Last but not least, what are some factors that can affect our bearing measurements?
Local attraction can interfere with compass readings, right?
Exactly! Local attraction can cause errors due to nearby magnetic materials or objects. It’s crucial to check the difference between your fore bearing and back bearing to detect any issues.
What’s the significance of magnetic declination then?
Magnetic declination is the angle difference between true north and magnetic north. Remember to adjust for it as it varies by location and time. A quick way to recall it would be: 'Declination Direction Depends on Location.'
I see how understanding these factors is vital for accurate surveying!
Absolutely! Always stay aware of these influencing elements to ensure accuracy in your work.
Directions measured relative to meridians in surveying.
The north-south direction obtained through astronomical observations.
Direction indicated by a magnetic needle.
A complete circle of measurement from 0° to 360°.
A measurement not exceeding 90° related to north or south.
The angle between magnetic and true north.
Magnetic interference that can affect accuracy.
Bearings are neat, in a circle we show, North to South, and East to West flow.
Imagine a traveler who always consults their compass, turning first to the true north, then adjusting for the magnetic pull they feel from the compass needle. This story illustrates how bearings guide them safely as they navigate.
To remember the types of bearings: 'W for Whole, R for Reduced.'
Use 'TAKE NOTE' to recall: True and Magnetic, Adjust for Declination, Keep an Eye on Local Attraction!
Term
What is a True Meridian?
Click to flip
Term
What is Magnetic Declination?
Click to flip
Term
What is a Whole Circle Bearing?
Click to flip
Term
What is a Reduced Bearing?
Click to flip
The direction or angle of a survey line with respect to a reference meridian.
The direction established by the geographic north and south poles, based on astronomical observations.
The direction indicated by a freely suspended magnetic needle at a specific location.
An angle measured clockwise from the magnetic north, ranging from 0° to 360°.
The angle between a survey line and the north or south direction, always less than 90°.
Instruments used to determine magnetic bearings, including different types like prismatic and surveyor's compass.
The angle difference between the magnetic north and the true north.
Errors in compass readings caused by nearby magnetic materials or objects.
This section covers the concept of bearings in surveying, including types of meridians and how bearings are measured.
This section explains bearings as the directions of survey lines concerning meridians. It introduces the true and magnetic meridians, types of bearings, magnetic compasses for measurements, and considerations like magnetic declination and local attraction that affect the accuracy of bearings.
In surveying, bearings refer to the direction of survey lines concerning a reference meridian. There are two main types of meridians: true meridian, based on astronomical observations, and magnetic meridian, derived from a freely suspended magnetic needle. Bearings can be classified into two types: Whole Circle Bearing (WCB), which is measured in a clockwise direction from north, and Reduced Bearing (RB), which measures angles from the north or south towards the east or west. This section also highlights different magnetic compasses used in surveying, discusses associated factors like magnetic declination and local attraction, and emphasizes their impact on measurement accuracy. Understanding bearings is crucial for accurate surveying, especially during traverses.