lähtötasot
Lähtötasot are reference elevations used in surveying, construction, and cartography as the starting point for vertical measurements. They form a local or project-specific vertical datum, providing a common baseline from which heights, depths, and terrain elevations are calculated. By defining a stable set of starting levels, different datasets and drawings can be aligned and compared consistently.
Establishing lähtötasot typically involves a leveling survey to create a network of benchmarks with known elevations
In daily practice, elevations in plans and digital models are expressed as values above the chosen lähtötaso.
In Finland and other countries with established surveying traditions, vertical reference systems are maintained by national