ISO 12858-2:2020

Overview - ISO 12858-2:2020 (Tripods for geodetic instruments)

ISO 12858-2:2020 specifies essential requirements for telescopic tripods used with geodetic and surveying instruments. The standard ensures mechanical compatibility and reliable performance when joining instruments and tripods from different manufacturers. It applies to tripods for levels, theodolites, tacheometers, GPS equipment, EDM instruments and assemblies with targets, reflectors or antennae.

Key topics and technical requirements

• Tripod types and heads: Defines two main tripod categories - Type L (light-weight, flat head LF or spherical head LS) and Type H (heavy-weight).
• Mechanical dimensions: Minimum/maximum lengths, platform and rotating-piece diameters and clearances are specified to enable interchangeability (see standard for full dimension tables).
• Clamping screw and connection:
  • Thread: 5/8 in bolt thread on the clamping screw and matching nut on instrument base plate.
  • Hollow screw: internal bore ≥ 8 mm to allow optical centring devices.
  • Centring accuracy: plumb suspension arranged to secure 2 mm centring accuracy.
• Torsional rigidity: Tripods must withstand applied torsion without lasting deformation. Residual torsion limits after a standard test are 10″ (3 mgon) for Type L and 3″ (1 mgon) for Type H.
• Height stability under load: With double the maximum instrument mass applied, headplate sinking must not exceed 0.05 mm.
• Joints and friction: Leg joints must allow quick setup and have adjustable friction.
• Legs and shoes: Legs may be wood, metal or plastic (wood must be well-seasoned); shoes require a step and unhardened-steel tips.
• Materials & corrosion protection: Materials are at manufacturer discretion but all components must resist or be protected from corrosion; legs may be painted in warning colours.
• Tools and marking: Supply tools for hinge and leg-head adjustments; tripod must be marked with manufacturer name/trademark and may carry a formal designation.
• Normative refs: Uses ISO 9849 (vocabulary) and ISO 2768-1 (tolerances); Annex A covers Whitworth-form parallel screw threads.

Applications and who uses this standard

ISO 12858-2:2020 is essential for:

• Manufacturers of surveying tripods and geodetic instruments (ensuring interoperability and product specs).
• Product designers and engineers specifying mechanical interfaces (threads, bore sizes, head designs).
• Procurement and quality teams who require compliance criteria for purchasing and acceptance testing.
• Calibration labs and survey professionals who verify torsional rigidity, height stability and centring accuracy in field equipment.

Practical benefits

Following ISO 12858-2:2020 improves interoperability, safety and measurement reliability by standardizing tripod connection geometry, mechanical performance (torsion, load stability) and marking - making cross-brand use and field operations more efficient.