Optical Square Offsets: Correct Handling

When taking offsets using an optical square on the right hand side of the chain line, proper handling is crucial for accuracy.

Instrument Position for Right-Side Offsets

The optical square is used to establish perpendicular lines (90 degrees) relative to a primary line, like the chain line.

• To establish an offset to the right of the chain line, the surveyor stands directly on the chain line.
• The optical square is held in the left hand.
• The instrument must be held in an upright position.
• The surveyor sights back along the chain line through the instrument.
• Rotation occurs until the direct view of the chain line aligns with its reflection in the instrument's mirrors.
• This alignment establishes the line of sight perpendicular to the right, enabling sighting of the offset point.

Holding the instrument with the left hand and maintaining an upright orientation allows for correct viewing angles and mirror reflections needed to accurately site the offset point on the right side.

Final Answer Determination

Considering the required operation for measuring offsets to the right:

• Holding the instrument by the left hand is necessary for directing the sighting correctly.
• An upright position ensures the mirrors function as intended for establishing the 90-degree angle.

Therefore, the optical square is held by the left hand upright for taking offsets on the right hand side of the chain line.