This disclosure relates to a system for monitoring walls. The system receives first and second image data representing two-dimensional locations of multiple points of the wall associated with a first and second point in time, the second point in time being later than the first point in time. The system also receives depth data from a depth sensor indicative of a change in depth of the wall between the first point in time and the second point in time. The system then determines data indicative of a change of the two-dimensional locations of the multiple points of the wall between the first point in time and the second point in time based on the first image data, the second image data, and the depth data. This means correlations between the image data and the depth data can be considered, which allows accurate perpendicular line of sight monitoring.