Charles Eickhoff, 28th Maintenance Squadron calibration technician, looks through a technical order while performing precision measurements on Ellsworth Air Force Base, S.D., Feb. 16, 2012. Technical orders list exact specifications that allow the precision measurement equipment laboratory to calibrate instruments such as the altitude, air pressure, and oil pressure gages for accuracy. (U.S. Air Force photo by Airman Alystria Maurer/Released)