Accuracy of the application of mobile technologies for measurements made in headings of the Kłodawa Salt Mine

The “Kłodawa” salt mine, due to geological conditions and continuous salt extraction, is subject to a range of measurements documenting the speed of changes in the geometry of the chambers. Cyclic surveys are conducted under challenging conditions several hundred metres underground. Consequently, measurement methods used for determining the parameters of the ongoing clamping should be of high precision but also be resistant to dense dust (in fields of active mining) and strong gusts (near ventilation shafts). The research presented here concerns the analysis of the possibilities of solutions offered by modern technologies in mine conditions. Test measurements were conducted at observation stations using linear bases stabilized with metal pins. The base points were located in the aisles, ceiling, and bottom of the chamber in Field 1 of “Kłodawa” salt mine at the depth of 600m. Point clouds mapping the object were acquired using a Leica RTC360 3D laser scanner and two mobile devices: Motorola G100 smartphone and iPad Pro with LiDAR technology using the Pix4Dcatch application. The accuracy of the point cloud from the Leica RTC360 3D laser scanner was determined by comparing it with classic measurements taken with a Leica Disto laser rangefinder. The repeatability and accuracy of the point cloud from a smartphone were examined using statistical analysis based on Pearson’s correlation coefficient and cross-correlation. An attempt was also made to approximate the correlation between the obtained errors and two parameters: the number of images and the size of the object.