Techniques and systems for gradient search are provided based on sensing or measuring at selected locations of a target object without performing full-field sensing or measuring over the entire field of the target object. Search methods are provided to include determining a coordinate of a boundary of a region in relation to a loop in a proximity of a first location, determining a direction of a gradient of the coordinate corresponding to the first location, and selecting a second location based on the determined direction. A search system can be implemented to include an imaging system to determine a coordinate of a feature of an object on a loop in a proximity of a first location, and a controller, coupled to the imaging system, to determine a direction of a gradient of the coordinate corresponding to the first location, and to select a second location based on the determined direction.
