Given the urgency of the task and the need to accurately identify and map stone walling while minimizing disturbance to archaeological sites, the best approach among the options provided is:
**2. Carry out an airborne LiDAR survey of the study area.**
Airborne LiDAR (Light Detection and Ranging) is a highly effective remote sensing technique that can penetrate vegetation canopies and produce detailed topographic maps, revealing features such as


