Civil Engineering May 2021 | Vol 29 No 4

Civil Engineering May 2021 33 The corrections associated with the base station are transmitted over the internet for increased accessibility in the Pretoria region. The mobility provided by the hardware enables diverse application, ranging from MVS techniques which require an absolute reference frame for successful reconstruction (see Figure 3) to direct antenna surface mapping (RTK-ASM) techniques for more intricate applications such as preservation of historical structures. Research activities associated with advancements in sensory capabilities and alternative geolocation services serve as the catalyst for realising robust digital twins in the 4IR era. TRAIN (DEFECT) DETECTIVES With the increased reliance on rail as a form of public and freight transport, the rate of degradation of railway tracks and the resulting decrease in passenger com- fort (for passenger trains) have become important aspects for further research. This forces researchers to develop faster, cheaper methods of detecting track defects – a task that is of high importance within the spectrum of predictive maintenance. One such method is ana- lysing vibration data from the accelerom- eters installed on asset tracking terminals (commonly known as tags) installed on railway vehicles. Asset tracking terminals are installed on railway vehicles for organisations to track their movements with the GPS that is installed as part of the terminal. An accelerometer is installed to power up the terminal whenever a large enough vibration is detected so that the terminal can record a time and location. The magnitude of the induced vibration is also recorded. This data can easily be accessed and downloaded from online dashboards to which the recorded data is uploaded. With hundreds of terminals on a single train passing over a particular defect, the analysed data will indicate that there may be a defect present at a specific location. Maintenance engineers can then send professionals to assess the defect. Using this inexpensive equipment installed on railway vehicles to detect the presence of track defects alleviates the need to send out expensive and time-con- suming geometry cars on a regular basis. The added benefit of these terminals is that other occurrences may be detected, such as railway vehicle coupling disloca- tions or vehicle speed. The flexibility of the uses of the asset tracking terminals, together with their low cost and ease of data acquisition, enables organisations to effectively and ef- ficiently detect the presence and locations of track defects from their workstations, at a low cost, using revenue-earning trains to do so. To test this novel track defect detec- tion method, accelerometers and termi- nals have been installed on UP’s Road/Rail Vehicle (RRV) (see Figure 4) and prelimi- nary results have been obtained. The ex- pectation is that much will be learnt from Figure 4 UP’s RRV with vehicle-track response monitoring Using this inexpensive equipment installed on railway vehicles to detect the presence of track defects alleviates the need to send out expensive and time-consuming geometry cars