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1

Long range measurements using a contactless low cost optical sensor

Krelling P C L, Gonzalez-Jorge H., Armesto J., Arias P.

Optica Applicata

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2013

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Vol. 43, nr 3

435--440

EN

Length measurement is very common in many industrial applications and there is a number of instrumentation involved, mainly dependent on the range and accuracy requirements. In this work, a contactless optical measurement unit is developed. It is based on a mouse sensor and an external laser source. The system is calibrated using an optical board and an electronic distance measuring system. Accuracy and precision of the system is evaluated using the reference data from a total station. Values of 1 mm and 0.3 mm are respectively obtained. Length range during the experiment is 8.5 m. The data of the optical measurement unit are compared with those obtained from a commonly used wheel encoder. Results from the optical sensor of the mouse improve the encoder data.

2

Evaluation of road signs using radiometric and geometric data from terrestrial LiDAR

Gonzalez-Jorge H, Riveiro B., Armesto J., Arias P.

Optica Applicata

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2013

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Vol. 43, nr 3

421--433

EN

Maintenance works are crucial to reduce the risk of accidents. Road signs appear to be one of the most important elements for safety purposes so their inspection is commonly included in the most extended road management systems. The geometric state of the sign is of great importance, especially interesting is its flatness and the inclination relative to the ground. Road signs are printed with reflective paints to maximize the visibility to the drivers. This coating produces a high reflected radiation that is easily recorded by the photoelectric detector of the laser scanner mechanisms. It allows establishing an intensity based filter in order to perform the 3D classification of the road sign. In this work, a number of road signs are evaluated, under a geometric point of view, using the laser scanner Riegl LMS Z390i. A Matlab algorithm is developed for all the data processing (3D classification and evaluation of geometric parameters). Results do not show the evidence of folded or abnormally tilted signs. The developed algorithms open the possibility of using the attribute of intensity of laser scanning data for classification purposes, during the automatic evaluation of the condition state of road signs. Such algorithms could increase the productivity and reliability of the inspection works.

3

Novel method to determine laser scanner accuracy for applications in civil engineering

Gonzalez-Jorge H., Solla M., Armesto J., Arias P.

Optica Applicata

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2012

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Vol. 42, nr 1

43-53

EN

One of the most important aspects of controlling the condition of civil engineering structures is the deformation monitoring. 3D laser scanners show some advantages related to the controlling of unexpected deformations which cannot be monitored with total stations or levels. Technical datasheets provided by laser manufacturers give the accuracy of single point measurements, although these figures can be improved using fitting algorithms. This paper depicts a novel technical procedure used to detect real accuracy that can be achieved using surface fitting techniques. This technique is based on the displacement of an aluminum plate by means of a precision actuator. Shift produced in the plate is measured by a laser scanner and a total station. Accuracy is evaluated as the difference between the values given by the actuator and those provided for the geodetic instruments. The procedure has been tested using a laser scanner RIEGL LMS Z390i and a total station Leica TCR 1102. The results obtained are very close in both cases and depict values of accuracy less than 1 mm. These results confirm the possibilities of the RIEGL system to detect small deformations. It can be concluded that this system can be used in the monitoring of civil engineering structures. On the other hand, the single point measurement exhibits an accuracy around 6 mm and confirms the data provided by the manufacturer of the laser scanner.