# Monitoring and Data Analysis in Small-Scale Landslide Physical Model
## 5 Discussion  
The main advantage of landslide monitoring, as well in the field and in small-scale models, using different noncontact methods such as high-speed cameras and terrestrial laser scanner, is the ability to observe landslide development and movements without a soil disturbance, with high spatial resolution, and to obtain data in a relatively short period of time. There is no equipment, especially inside the physical model or at its surface, which could have any effect on the slope behavior. The relatively new method of landslide surface changes monitoring using high-speed cameras needs to be adjusted to the conditions of landslide occurrence in different environments of the conducted small-scale tests. Several issues are identified as not reliable and should be resolved in the future tests. Visibility of reference points in both of the cameras was sometimes obstructed by the elements of the model platform or appearance of shadows from surrounding objects. This can be solved by better lighting conditions from different directions of the lights. Recognizing of the marking pins is a less important yet still significant problem in surface changes monitoring. White pins with black spots used in Tests 2 and 3 in comparison to standard labels from the manufacturer used in Test 1 proved to be less visible, recognized, and observed by the set of cameras. The nature of the tests, with rainfall droplets on pins and water accumulation on a slope surface, makes them less able to be observed during all test stages, and some loss of measurement values is imminent. To increase accuracy and avoid losses of measurement data, the standard size labels should be used, tilted to face both cameras. The introduction of an additional set of cameras in the system (if possible) could be the best solution, as the 12 M camera system is precise enough to be able to track not just the reference points but the soil particles too. Results of the terrestrial laser scanning may depend on the experience of the operator, and it is crucial to define what kind of results are expected from the scans and what kind of object is the target of the scans. Selecting the better resolution and quality can significantly affect the accuracy of the data and eliminate the noise that is gathered with the data but that increases scan duration and the number of points for later processing. Although the laser scanner can be very precise, it is necessary to determine the optimum between the time spent in recording and processing the data and the final result obtained as a high-resolution 3D point cloud. It is recommended to conduct more SfM surveys with more photographs taken in a particular survey, especially in the final stages of the sliding, and more attention should be paid to the details of the test such are good and constant lighting, the positions of formed cracks in the slope, and the use of the static reference points for better accuracy. Although not so precise as a terrestrial laser scanner, due to the particularity of this kind of survey, the combination of both methods would mean more postprocessing time but also more accurate results in monitoring movement of the landslide. To ensure reliability of measured values during the tests, all the embedded sensors were calibrated and tested in the soil material outside of a slope model to validate the sensor readings. All carried-out tests were also controlled, leaving the results tracking in the stages after tests (after artificial rainfall stopping and during the water seepage from the model till the reaching of conditions relatively close to initial conditions in the slope). It was confirmed that all the sensors were working correctly and measuring data within the expected values corresponding to the processes that are taking place in the slope. Tensiometers' ability to measure both negative and positive pore pressure is particularly important in the lower part of the slope where, if not drained, the water would cause the occurrence of positive pore pressure with the rising of the groundwater level.