This paper compares effectiveness of the different approaches of computing the tilt angle of the horizontal gradient amplitude and tilt angle of the analytic signal amplitude such as use of direct expression and frequency domain technique (also called k - function) in terms of their accuracy on the detection of the edges of magnetic and gravity sources. These approaches were performed on both synthetic magnetic and gravity data where the frequency domain technique shows improvements in delineation of the actual edges of the sources compared to the direct expression. Additionally, real magnetic data from Zhurihe (Northeast China), and real gravity data from Tuan Giao (Northwest Vietnam) was considered and the obtained results from applying the different approaches were compared with known geological structures. The results show that the boundaries detected from the use of the frequency domain technique are in accord with the known geological structures.