Indicating the relative reliability of data or of an interpretation, an important aspect of interpretation. Usually a subjective process. Sometimes grading systems employ letters: vg=very good, g=good, f=fair, p=poor, vp=very poor, and ?=questionable. Coherency-measuring criteria are sometimes used in an attempt to make grading quantitative. Contours are often graded by varying the type of line: solid contour=reliable; dashed contour=less reliable or interpolated between data; and dotted contour=speculative.