There may be some variation in measuring ad space in different publications. Here are the definitions of column inch, standard advertising unit and pica.
Column Inch: Display advertising's primary space measurement. This is generally one column wide by one inch deep. it may vary by publication.
Standard Advertising Unit (SAU): Ad size formats that may be accepted in different daily newspapers. This standard was created to make it easier for a large advertiser to place the same ad in many different newspapers without adjusting the ad to different column specifications.
Pica: A typographic unit of measurement: 12 points = 1 pica or 1/6” (0.166”), and 6 picas = 1” (or 0.996”).
