Benchmark

A benchmark is a permanently established point with precisely determined elevation above sea level. Benchmarks serve as reference points for all types of height measurements in surveying and construction.

Types of benchmarks:

• State benchmarks - leveling network points (maintained by LGIA)
• Local benchmarks - created for construction site or project
• Wall benchmarks - embedded in building foundations or walls
• Ground benchmarks - concreted in ground

Benchmark construction:

• Metal pins - most commonly used, corrosion resistant
• Cast iron benchmarks - classical wall solution
• Concrete posts - with metal marker
• Bedrock cuts - very stable

Benchmark installation:

1. Selection of stable location (outside construction zone)
2. Benchmark securing (concreting, embedding)
3. Height transfer from state network
4. Documentation (coordinates, description, photo)

Benchmark usage:

• Construction - height control, floor elevations
• Topography - height connection
• Deformation measurements - stable reference
• Utilities - pipeline gradient control

Benchmark stability:

Benchmark stability is critical - they must be:

• Below frost depth (deeper than 1.5 m)
• On stable foundation (not on fill)
• Protected from mechanical damage
• Accessible for measurements

Height transfer:

Height is transferred from benchmark by leveling:

1. Level setup between benchmark and measured point
2. Reading on benchmark
3. Reading on new point
4. Height calculation

Latvian leveling network:

Latvia has more than 6,000 state leveling benchmarks forming the height reference system LAS-2000.5. Benchmark data is available in the LGIA database.