Camera calibration

A method for calibrating one or more imaging devices carried by an unmanned aerial vehicle (UAV), the method comprising:

• receiving, from the one or more imaging devices, a plurality of images of a calibration target, the calibration target comprising a plurality of features arranged in a repeating pattern and a plurality of reference markers, wherein the plurality of reference markers are each uniquely identifiable in each image of the plurality of images, wherein each of the plurality of reference markers on the calibration target forms one of vertices of an irregular polygon on the calibration target with no more than two of the plurality of reference markers being on a same line, wherein each of the plurality of reference markers in each image of the plurality of images forms one of vertices of an irregular polygon in the each image of the plurality of images, and wherein the plurality of images comprises at least one image capturing less than all of the plurality of features;
• determining, with aid of one or more processors, a spatial relationship between the plurality of reference markers in each image of the plurality of images and the plurality of reference markers on the calibration target, comprising identifying a correspondence between the vertices of the irregular polygon in the each image of the plurality of images and the vertices of the irregular polygon on the calibration target;
• formulating, based on the spatial relationship and with aid of one or more processors, a correspondence between image coordinates of features in each image of the plurality of images and global coordinates for corresponding features on the calibration target;
• determining, based on the correspondence and with aid of the one or more processors, calibration parameters for the one or more imaging devices;
• and
• generating, based on the determined calibration parameters for the one or more imaging devices, a 3D representation of an environment of the UAV based on the calibration parameters.