1. The problem states that the elevation of BM1 is 0. 2. Elevation in surveying or mapping refers to the height of a point relative to a reference level, often sea level. 3. Since the elevation of BM1 is given as 0, it means BM1 is at the reference level. 4. No further calculations are needed unless additional data or points are provided. 5. This serves as a baseline or benchmark for measuring elevations of other points.