How far should the wingtip be from an obstruction during taxiing to estimate 25 feet clearance?

When estimating the clearance needed during taxiing, it is important to consider the overall dimensions of the aircraft and the proximity to potential obstructions. To achieve a clearance of 25 feet, the safest practice is to measure from the base of the obstruction. This allows for a buffer zone that accounts for the distance from the wingtip to the ground and any potential deviations in height or placement of the obstruction.

Measuring from the base ensures that any part of the obstruction does not pose a risk to the wingtip during taxiing, particularly since aircraft can have variations in wing height and the likelihood of proximity to uneven terrain or items extending from the obstruction itself. By focusing on the base, pilots can ensure that they maintain appropriate distance and avoid potential accidents. This approach emphasizes the importance of visualizing the aircraft's clearance in relation to fixed structures, which is a crucial skill for safe ground maneuvering.