The aging of infrastructure challenges many industrialized countries. As the age of structures increases, the risk of corrosion for reinforced concrete structures also rises. Corrosion of the reinforcement is the most common cause of premature maintenance of road traffic infrastructure. Consequently, the importance of condition assessment and monitoring will increase in the future. On the one hand, to minimize the expected rise in maintenance costs, and on the other hand, to ensure the safety of users. Unfortunately, there is currently a lack of non-destructive inspection methods for structures such as retaining walls, which are partially covered by soil and cannot be reliably inspected visually.