Traversing Surveying Fundamentals

Traversing is a fundamental surveying technique used to establish the relative positions of points by measuring the lengths and directions of a series of connected lines. These lines form a traverse, which can be open or closed. The direction of each line is crucial for accurately mapping the area.

Magnetic Meridian in Surveying

The magnetic meridian at any given point on the Earth's surface refers to the direction indicated by a freely suspended magnetic needle when it comes to rest, aligning itself with the local direction of the Earth's magnetic field. It serves as a primary reference direction for determining the bearings or directions of survey lines in compass surveying.

Loose Needle Method Explained

The question describes a specific method of traversing where:

• The direction of the magnetic meridian is precisely established at each traverse station.
• The direction of the survey line (or its bearing) is subsequently determined by taking a reading with reference to this newly established magnetic meridian at that particular station.

This precise procedure is the defining characteristic of the Loose Needle Method of traversing. In this method, for every setup at each new traverse station:

• The compass instrument is carefully set up over the station point and leveled accurately.
• The magnetic needle within the compass is then allowed to swing freely and settle naturally. When it comes to rest, it indicates the local magnetic meridian.
• The bearing of the traverse line is then read directly by sighting along the line while ensuring the compass's zero mark aligns with the magnetic north indicated by the loose needle.

This approach allows for continuous checking and adjustment for local magnetic attractions at each traverse station, as the magnetic meridian is re-established independently at every point.

Comparison with Other Traversing Methods

To clarify why the Loose Needle Method is the correct answer, let's briefly consider the other options in the context of traversing:

• Fast Needle Method: Unlike the Loose Needle Method, in the Fast Needle Method, the magnetic needle is often clamped or fixed in a specific orientation relative to the instrument. Instead of re-establishing the magnetic meridian at each traverse station, angles are typically measured directly between successive lines, or bearings are carried forward from a single initial bearing established at the first station. The needle is 'fast' because it might be arrested, and readings are taken relative to a fixed zero, not a free-swinging needle at every point.
• Bearing Method: This is a general term. Both the Loose Needle Method and the Fast Needle Method use bearings to define line directions. However, 'Bearing method' alone does not specify the unique technique of establishing the magnetic meridian at each individual traverse station as described in the question.
• Fixed Needle Method: This term is generally interchangeable with the Fast Needle Method. It implies that the magnetic needle is not allowed to freely align with the magnetic meridian at every setup. It contradicts the specific condition mentioned in the question, which is central to the Loose Needle Method.

Conclusion on Traversing Methods

Given the detailed description in the question, where the magnetic meridian is established at each traverse station and used as a reference to determine the direction of the line, the method of traversing being described is unequivocally the Loose Needle Method.