Many robotic operations, e.g. , mapping, scanning, feature following, etc. , require accurate surface following of arbitrary targets. A versatile surface-following and mapping system using a very high precision "eye-in-hand" proximity sensor, designed to provide hardware, software, and application independence, modular development, and upward expandability, is presented. These goals are met by a full a priori specification of the hardware and software interfaces; a modular system architecture; and a hierarchical surface-data analysis method, permitting application-specific tuning at each conceptual level of topological abstraction. This surface-following system was fully designed and implemented independent of any specific robotic host and then successfully integrated with and demonstrated on two very dissimilar real-time robotic systems. Presented in detail are the hardware and software architectures, the mapping and terrain forecasting algorithms, and the applications' environments and task requirements.