Improving the horizontal boundaries of subsurface geological structures is one of the main objectives in interpreting potential fields. To solve this problem, a number of different algorithms have been introduced based on the derivatives of the field. However, these algorithms have some drawbacks, e.g., the determined edges do not match the actual boundaries. Here, we present a new algorithm based on the gradient amplitude and its derivatives which yields more precise and clear boundaries. The robustness of the proposed technique is illustrated using theoretical examples and a real example from Kon Tum province, Vietnam. Our results show that the proposed technique can produce results with better resolution and minimizes the artifacts in the pseudo-boundary map.