Systems and methods are described for automatic calibration of robotic mechanism functions according to accurate decoding and locating of target features using spot scanning. For example, a robotic mechanism in a storage library has one or more integrated scanners that can acquire contrast and/or topographic scan data from a scan window that represents a profile of the scan window expected to have one or more target feature sets. The scan data can be decoded according to predefined target masks (e.g., target type-specific fit tables) at a number of decode threshold levels to estimate target feature values, which can be used to converge on (or otherwise generate) a purported target definition with purported feature values. The purported target definition can be used to facilitate various functions, such as automatic calibration of robotic mechanism positioning and object identification.