ISO 17123-7:2005

Overview

ISO 17123-7:2005 - "Optics and optical instruments - Field procedures for testing geodetic and surveying instruments - Part 7: Optical plumbing instruments" - defines in-situ field procedures to determine and evaluate the precision (repeatability) of optical plumbing instruments and their ancillary equipment used in building and surveying measurements. The standard is intended as a practical verification of an instrument’s suitability for an immediate task (not as a comprehensive factory acceptance test) and supports uncertainty assessment in accordance with the ISO Guide to the expression of uncertainty in measurement (GUM).

Key topics and requirements

• Scope & exclusions: Applies to optical plumbing instruments (including spirit-level, single-compensator, two-compensator, and laser‑emitting plumbing instruments). Not applicable to optical plummets used inside tribrachs or surveying instruments.
• Field‑oriented testing: Procedures are developed for in situ verification without special ancillary lab equipment, minimizing atmospheric and adjustment effects.
• Target and grid: A rectangular x–y grid target plate is required. Grid spacing t (in mm) is specified relative to plumbing height h (m) and telescope magnification Γ; the standard provides the formula and definitions for selecting t so the grid resolution matches the plumbing height and optics.
• Measurement protocol:
  • Allow instrument to acclimatize (≈ 2 minutes per °C difference) and check collimation per manufacturer instructions.
  • Perform three series (m = 3); each series has 10 sets (n = 10) of measurements.
  • Each set consists of observations in diametrically opposite telescope positions I and II for the x- and y-directions (xI, xII, yI, yII).
  • Between series, lift and re‑set the instrument to simulate repeat setups.
• Calculations & statistics:
  • Compute deviations δx, δy (differences between opposite observations) and quasi‑observations (means).
  • Residuals lead to experimental standard deviations s_x, s_y and s_total for the plumbing height h.
  • The standard prescribes statistical tests to evaluate repeatability, compare samples, test equality of x and y component variances, and check coincidence of line of sight with the plumb line; degrees of freedom used in examples are given (e.g., ν = 9 for components, total ν = 54).

Applications and users

• Practical field verification for: surveyors, geodetic technicians, building survey teams, construction layout engineers, calibration personnel, and quality managers.
• Use cases: pre-job instrument checks, periodic in-field verification of optical plumb precision, comparing instruments under similar field conditions, and as an initial step when assessing measurement uncertainty for vertical control and setting-out tasks.

Related standards

• ISO 17123 series (Parts 1–6) - theory and procedures for levels, theodolites, EDMs, tacheometers, rotating lasers
• ISO Guide to the expression of uncertainty in measurement (GUM)
• ISO 7077 / ISO 7078 / ISO 4463-1 - building measurement and setting-out procedures

Keywords: ISO 17123-7, optical plumbing instruments, field procedures, geodetic instruments, surveying instruments, precision, repeatability, plumbing height, measurement uncertainty, in situ testing.