Methods, apparatus, and articles of manufacture to detect shapes are disclosed. Example methods disclosed herein include determining a first likelihood of detection for a reference shape at a first distance from an image capturing device, and storing the reference shape in a first group of a plurality of groups in the database based on a comparison of the first likelihood of detection with a first threshold, the first group associated with the first distance. Disclosed examples also include selecting reference shapes of the first group to compare to an object outline detected in an image in response to a query, the query including a depth value associated with the detected object outline, the selecting of the reference shapes of the first group based on the depth value.