Describe the significance of an 'as-built' survey in tower management and its use in future modifications.

An 'as-built' survey holds significant importance in tower management as it provides a precise record of the tower's actual constructed dimensions, locations, and configurations, which may differ from the original design plans. This survey is conducted after the tower has been built or modified, and it documents the exact positions of all tower components, antennas, and other equipment. The as-built survey is crucial for future modifications because it provides the most accurate baseline data for structural analysis. When planning to add new antennas or make other changes to the tower, engineers rely on the as-built survey to create a realistic model of the tower and assess the impact of the proposed modifications. Using the as-built data ensures that the structural analysis is based on the actual tower configuration, rather than potentially inaccurate design plans, leading to more reliable results and safer modifications. It also helps in identifying any discrepancies between the design and the actual construction, which can be critical for ensuring the tower's structural integrity.