A PROTOTYPE OF LASER RANGEFINDER FOR MEASURING RAILWAY TUNNEL CROSS-SECTION

In 2016, State Railway of Thailand (SRT) developed a prototype of laser range finder for measuring railway tunnel cross-section by using laser range finder together with angle protractor. After that, the laser distance meter had been further developed into a new model in 2020. This new model used the handheld laser range finder which has its own buildin angle displayed functions. Therefore, the new model design, the big and heavy steel angle protractor had been removed which made it easy to be operated and transported. However, these two developed models still require operator for manually adjusting the angle of measurement and still need time to be operated. Thus, the purpose of this research was to develop the next generation of the device capable of automatic operating as well as automatic data collection stored in a small SD card for easily data transferring to a computer. The study method was started from, structural design, built and assembly, design of electronic devices and assembly, calibration with standard measuring devices and finally measuring the real tunnel at Khao Pang Hei tunnel located at the northeast railway route of Thailand. The study results showed that 1) the measuring results between the developed device compared with other basic and standard devices, i.e., the total station, handheld laser range finder and measuring tapes were similar. There were only some angles that showed differences not more than ± 2 millimeters, 2) The measuring results on tunnel models (building hallway and similar structures) compared to those standard devices were similar with differences not more than ± 3 millimeters. In addition, the measuring time used for each measurement was only 6-7 minutes for a crosssection and 3) The measuring results of the real tunnel comparing with the total station, handheld laser distance meter, and measuring tapes were

similar. There were only some angles that showed

the differences not more than ± 3 millimeters. Then,

these accepted measured data were used to

generate the tunnel cross section in a computer

drawing program. The drawing was capable to be

reliably utilized as a reference and precisely

compared to the railway structural and loading

gauges. Consequently, the new prototype of laser

range finder for measuring railway tunnel crosssection can be used effectively for measuring the

tunnel cross-section dimension for railway and can

be used further by SRT to evaluate all safety and

maintenances in railway tunnels nationwide.