Image Processing

Calibrating and certifying measuring instruments is a time comsuming, manually executed task. The operator has to read several imes during an often lengthly procedure the display of the instrument to be certified and compare it to the reference value from the reference instrument. The instruments to be certified exhibit a large variety of forms, shapes, and display types. Reference instruments have a digital output that can be connected to a computer for reading, instruments to be certified mostly not.


We have developed a software system that helps to automize the calibration procedure by various means:

  • A digital camera is used to capture the displays of one or various instruments during the measuring procedure.
  • The display areas can be marked interactively by the operator.
  • The snapshots are taken according to the protocol specifications for this kind of instrument at the same time as the reference data is read.
  • Both the images (or only the marked areas) and the reference data are stored into a database.
  • The operators workload is reduced to set-up the system and to read the snapshots according to the established procedure.


To further improve the system, we have implemented

  • an automatic detection of the display areas and their rectanglur alignment (correctable interactively by the operator) and
  • an automatic reading of the digits of the display (correctable interactively by the operator).


The fully automaic reading has a precision of more the 98% tested on more than 1400 displays.


  • During the joint work with LOMG we developed the system SreC, which is capable of reading automatically digital displays.

Financed Projects


People Involved

Student Work


More about Laboratorio Oficial de Metrología de Galicia (LOMG)
Laboratorio Oficial de Metrología de Galicia (LOMG)
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Grupo de Procesado de Imagen y Realidad Virtual
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Laboratorio de Informática Aplicada