what does 0 mean in terms of elevation?

Answer 1

In terms of elevation, "0" typically refers to sea level. Sea level is considered the baseline for measuring elevation or altitude. Elevations above sea level are indicated with positive numbers, while elevations below sea level (such as in bodies of water, some valleys, or depressions) are indicated with negative numbers. For example, an elevation of +100 meters means the point is 100 meters above sea level, while an elevation of -50 meters means it is 50 meters below sea level.