Surveying Bearings: A Compass to Your Land's True North

Surveying bearings are the means by which we establish and measure angles on the surface of the Earth. They are a fundamental skill for any surveyor or engineer, and they are used in a wide variety of applications, from property boundary surveys to large-scale construction projects.

What is a Bearing?

A bearing is an angle measured clockwise from a reference direction. In surveying, we typically use true north as our reference direction, but other reference directions can be used, such as magnetic north or grid north.

Bearings are expressed in degrees, minutes, and seconds (DMS) or in decimal degrees (DD). DMS bearings are written in the following format:

DD° MM' SS"

where DD is the degrees, MM is the minutes, and SS is the seconds. Decimal degrees are written in the following format:

DD.dddd°

Types of Bearings

There are four main types of bearings:

• True Bearing: The angle measured clockwise from true north.
• Magnetic Bearing: The angle measured clockwise from magnetic north.
• Grid Bearing: The angle measured clockwise from grid north.
• Reduced Bearing: The angle measured clockwise from the nearest cardinal point (north, east, south, or west).

Measuring Bearings

Bearings can be measured using a variety of instruments, including compasses, theodolites, and total stations.

Compasses are the most basic tool for measuring bearings. They are simple and easy to use, but they are not as accurate as other instruments.

Theodolites are more accurate than compasses, and they can also be used to measure vertical angles.

Total stations are the most accurate and versatile instruments for measuring bearings. They can also be used to measure distances, elevation, and other data.

Applications of Surveying Bearings

Surveying bearings are used in a wide variety of applications, including:

• Property boundary surveys
• Construction projects
• Road and highway design
• Mining and drilling
• Environmental surveys

Tips and Tricks for Surveying Bearings

Here are a few tips and tricks for surveying bearings:

• Use a consistent reference direction. Always use true north as your reference direction, unless otherwise specified.
• Be aware of magnetic declination. Magnetic declination is the difference between true north and magnetic north. It is important to know the magnetic declination in your area before taking any measurements.
• Use the correct instrument for the job. Compasses are suitable for small-scale projects, while theodolites and total stations are better suited for larger-scale projects.
• Take multiple measurements. Always take multiple measurements to ensure accuracy.

Pros and Cons of Surveying Bearings

Pros:

• Accurate and reliable
• Easy to use
• Versatile

Cons:

• Can be time-consuming to take measurements
• Requires specialized equipment
• Magnetic declination can affect accuracy

Stories

Story 1:

A surveyor was hired to survey a large property. He used a compass to measure the bearings of the property boundaries. However, he did not account for magnetic declination, and his measurements were off by several degrees. This resulted in a boundary dispute between the property owner and his neighbor.

Lesson learned: Always account for magnetic declination when taking bearing measurements.

Story 2:

A construction crew was building a new road. They used a theodolite to measure the bearings of the road alignment. However, one of the construction workers bumped the theodolite, and the bearings were thrown off by a few minutes. This resulted in the road being built in the wrong direction.

Lesson learned: Be careful when handling surveying equipment. A small mistake can have big consequences.

Story 3:

A mining company was drilling for oil. They used a total station to measure the bearings of the drill rig. However, they did not take into account the elevation of the drill rig, and their measurements were off by several feet. This resulted in the drill rig being placed in the wrong location.

Lesson learned: Always consider the elevation of the surveying instrument when taking bearing measurements.

FAQs

1. What is the difference between a bearing and an angle?

A bearing is an angle measured clockwise from a reference direction, typically true north. An angle is simply a measurement of the amount of rotation between two lines.

2. What is magnetic declination?

Magnetic declination is the difference between true north and magnetic north. It is caused by the Earth's magnetic field, which is not aligned with the Earth's geographic axis.

3. How do I account for magnetic declination when taking bearing measurements?

You can account for magnetic declination by using a compass that has a declination adjustment. You can also use a declination calculator to find the magnetic declination for your area.

4. What is the best instrument for measuring bearings?

The best instrument for measuring bearings depends on the accuracy and precision required. Compasses are suitable for small-scale projects, while theodolites and total stations are better suited for larger-scale projects.

5. How do I take a bearing measurement?

To take a bearing measurement, you need to use a compass, theodolite, or total station. Point the instrument at the target, and read the angle displayed on the instrument.

6. What are the applications of surveying bearings?

Surveying bearings are used in a wide variety of applications, including property boundary surveys, construction projects, road and highway design, mining and drilling, and environmental surveys.

Conclusion

Surveying bearings are a fundamental tool for any surveyor or engineer. They are used to