Plane-table (plan table) surveying: Identify the method of surveying in which field observations and map plotting proceed simultaneously in the field, so that the plan is drawn directly while sights are taken.

Introduction / Context:

Surveying methods differ in how data are observed and how the final plan is produced. Some methods require returning to the office for plotting from field notes, whereas others allow plotting on the spot. Recognizing which technique combines observation and plotting in real time is fundamental in engineering surveying and site planning.

Given Data / Assumptions:

• The question seeks the surveying method where observation and plotting are done together in the field.
• Standard equipment terms are used: plane table, alidade, trough compass, plumbing fork.
• No special geodetic corrections are implied; this is ordinary topographical/cadastral work.

Concept / Approach:

Plane-table (plan-table) surveying mounts a drawing board on a tripod, fixes a sheet to scale, and uses an alidade for sighting. Points are sighted and directly plotted by rays and distances (or by intersection/traversing), so the map grows as observations proceed, enabling instant checks and rapid small-scale mapping.

Step-by-Step Solution:

Verification / Alternative check:

Textbook procedures—radiation, intersection, traversing, and resection—are all executed directly on the board, confirming real-time plotting capability.

Why Other Options Are Wrong:

• Chain/compass: observations are recorded in field books; plotting is done later in the office.
• Tacheometry: uses theodolite/stadia; again plotted later unless combined with a plane table.
• Plane alidade triangulation only: not a standard stand-alone method name.

Common Pitfalls:

• Confusing tacheometric measurement with plane-table plotting; they can be combined, but the defining feature of simultaneous plotting belongs to the plane table.

Final Answer:

plan table surveying