The question asks to identify the equipment that is not typically used in plane table surveying.

Understanding Plane Table Surveying

Plane table surveying is a graphical method where field observations and plotting occur simultaneously. It uses a plane table, a drawing board mounted on a tripod, along with accessories to measure and record details directly onto a map sheet.

Analysis of Equipment

• Alidade: This is a core component used for sighting objects and drawing lines of sight on the plane table sheet. It is essential for plane table surveying.
• Trough compass: Used with the plane table to orient the map with respect to the magnetic north. It is a necessary accessory.
• U-frame: This typically refers to the stand or tripod that holds and supports the plane table, allowing it to be leveled and rotated. It is fundamental for setting up the instrument.
• Vernier Arm: A Vernier arm is a precision measuring device often found on instruments like theodolites or vernier callipers for measuring fractional parts of a scale division. It is not a standard part of the basic plane table surveying setup.

Conclusion

Based on the functions of the listed items, the Vernier Arm is the only component not typically associated with plane table surveying. The Alidade, Trough compass, and U-frame (or tripod) are standard equipment.