This thesis deals with the processing of visual data to find strip-like structures. The algorithm developed may be used, for example, to detect roads in satellite photographs or, veins in biological images. The strip data is refined during several steps. In the first step, all possible candidates for strips are nominated. These small and discontinuous strips are connected together to form layer strips. Some strips may be rejected because they do not match the parameter specification. The general strip finder is a conceptual operator and does not depend on any single point for its final result. In contrast, the low level difference operator developed is a point by point operator. The results of the low level difference operator reveals the strength of the conceptual operator.