A method involves receiving a test image of at least a portion of a test object which includes a test moiré pattern generated by superposing one or more reference gratings on one or more subject gratings. The method further involves analyzing one or more test beat lines in the test moiré pattern and calculating one or more test values based on the analysis of the one or more test beat lines. The one or more test values are a function of one or more rotational angles corresponding to the one or more subject gratings and a shape of at least the portion of the test object. The method also involves calculating one or more angular errors of the one or more subject gratings based on the one or more test values and one or more template values and sending a notification based on the one or more angular errors.