1. A method for mapping, comprising: projecting a primary speckle pattern from an illumination assembly into a target region; capturing a Plurality of reference images of the primary speckle pattern at different, respective distances from the illumination assembly in the target region; capturing a test image of the primary speckle pattern that is projected onto a surface of an object in the target region; comparing the test image to the reference images so as to identify a reference image in which the primary speckle pattern most closely matches the primary speckle pattern in the test image; and estimating a location of the object based on a distance of the identified reference image from the illumination assembly.