Measuring accuracy

What are favorable/unfavorable measuring conditions?
Favorable/average measuring conditions:

  • Materials with good reflecting characteristics, meaning they reflect the laser beam in a divergent (not mirrored) manner
  • Laser dot is brighter than the ambient light
  • Operating within the allowable temperature range (-10° + 50° C)
Unfavorable measuring conditions:
  • Highly reflective surfaces
  • Highly absorbant surfaces, such as wet or dark surfaces
  • Operating at the limits of the allowable temperature range
  • Not waiting for temperature calibration
  • Very intensive ambient light
  • Shimmering
  • For optical and safety reasons, do not measure against colorless liquids (water) or glass
What accuracy of my Leica DISTO™ can I expect when using the functions for indirect measurements?
Some Leica DISTO™ devices are offering the possibility of measuring heights or widths using indirect measurement functions with Pythagoras theorem or with inclination sensor. Generally it is recommended to measure any height directly at the object by using simple distance measurement. If this is not possible because the object is not accessible or a high accuracy is not needed measurements can be also taken with the indirect measurement functions.

How accurate is Leica DISTO™ at 0.5m, 1m … to 200m? The measurement deviation for Leica DISTO™ devices is not directly proportional to the measured distance. Therefore the accuracy of a Leica DISTO™ remains constant until a range specified in the manual. After this range the accuracy will change by a value proportional to the distance which is also specified in the operation manual. In many cases it will not exceed the maximum measurement deviation. The Leica DISTO™D330, for example, has an accuracy of 1mm up to 10m. After this the deviation will increase by 0.025mm per meter (so that at 30m the measurement will be off by 1.5 mm). After 30m the deviation will increase by 0.1mm per meter (at 100m the measurement deviation could be 8.5 mm).

Please note that measurement conditions may have an influence on the accuracy. The tolerance is not proportional to the measured distance, but rather, the same over the entire distance. However, over long distances, additional errors of +/-5 ppm (parts per million) (+/-0.5mm/100m) come into play.

What does the term "typical" in relation to the product accuracy mean?
Leica Geosystems specifies its DISTO™ for a standard deviation of 2б (Sigma). The term typical means for measurements under normal measurement conditions. Targets in very bright conditions or bad reflecting targets may have an influence on the measurement accuracy. The use of target plates or shading of the targetpoint is recommended, especially if high accuracy is required.

What is measuring accuracy?
Measuring accuracy is specified in accordance with ISO-recommendation ISO/R 1938-1971, with a statistical safety of 95% (2s, i.e. two-fold standard deviation). Typical measuring accuracy is based on average measuring conditions within the specified measurement range. It is not valid for special application functions and calculations, such as Pythagoras and is not valid in tracking mode (continuous tracking).

How can I monitor my measuring equipment on my own?
Monitoring of measuring equipment for Leica DISTO™ –users who perform the required monitoring themselves, in accordance with their quality management systems: Measure an easily accessible distance of 2 to 10 m with a distance measuring instrument approved by your national bureau of standards. Make 10 measurements over the same distance. Determine the deviation of your measurements from the actual distance and calculate the standard deviation from the results. Record the value and set the time for the next series of measurements. Repeat these check measurements regularly, especially before and after important measuring tasks. Mark the Leica DISTO™ with an”inspected” sticker and protocol the entire monitoring process. Your Leica DISTO™ meets the specified accuracy, if the standard deviation is equal to or less than the value stated as the typical standard deviation. A Leica DISTO™ checked on the test distance works with the specified accuracy over the entire specified measuring and temperature ranges.

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