Overview
ISO 80000-3:2006 - "Quantities and units - Part 3: Space and time" specifies names, symbols and definitions for quantities and units used to describe space and time. It standardizes how lengths, angles, positions, time intervals and related units are named and represented, and provides conversion factors where appropriate. The part is one element of the ISO 80000 series (quantities and units) prepared in collaboration with IEC.
Key topics
- Core scope: definitions and recommended symbols for space- and time-related quantities (examples include length, breadth, height, thickness, radius, diameter, path length, distance, Cartesian coordinates, position vector, displacement, radius of curvature).
- Unit presentation and hierarchy: coherent SI units given first, followed by non‑SI units accepted for use with the SI; deprecated units and other non‑SI units are placed in informative annexes (CGS units; foot–pound–second based units; other units with conversion factors).
- Dimensionless quantities: guidance that the coherent unit for dimensionless quantities is the number one (symbol 1); treatment of plane and solid angle (radian and steradian are dimensionless derived units but may be used to clarify quantity type).
- Logarithmic quantities: conventions and units for levels and logarithmic measures (neper Np as coherent unit for natural logarithm definitions; bel B and decibel dB for base‑10 logarithms), including the conversion 1 B = (1/2) ln 10 Np ≈ 1.151293 Np.
- Numerical notation and uncertainty: use of symbols “=”, “≈”, “:=” and the recommended parenthetical uncertainty format (e.g., 2.34782(32) m) to express standard uncertainty on last digits.
- Table organization: quantities on left-hand pages with associated units on the right; annexes A–C supply additional unit details and conversion factors.
- Normative reference: ISO 8601:2004 for date and time representation.
Applications and users
ISO 80000-3 is practical for professionals who need consistent, unambiguous representations of spatial and temporal quantities:
- Metrologists and calibration laboratories (consistent unit usage, uncertainty notation)
- Engineers (mechanical, civil, aerospace) and designers (clear unit symbols and definitions)
- GIS, surveying and mapping professionals (coordinates, distances, angles)
- Software developers and data modelers (unit handling, interoperability, use with ISO 8601)
- Standards writers, technical editors and scientific publishers (consistent symbols and notation)
- Instrument manufacturers and test houses (unit labelling and conversion conventions)
Related standards
- ISO 80000 series (Parts 1, 2, 4, 5, …) for general rules, mathematical symbols, mechanics, thermodynamics, etc.
- IEC 60027-3 on logarithmic quantities and units
- ISO 8601 for date/time formats
ISO 80000-3:2006 supports clear, interoperable communication of space and time quantities across engineering, science and information systems, promoting accurate measurement, data exchange and documentation.
