A polycrystalline scintillator for detecting soft X-rays, which comprises Ce as a light-emitting element and at least Y, Gd, Al, Ga and O, and has a garnet crystal structure, and a composition represented by the general formula of 3+a5\u2212aO12, wherein 0\u2266a\u22660. In one embodiment, Presentation Time is converted to Data Time, and Data Time is reported instead of Presentation Time when only one time can be reported. The OLED display also includes a plurality of pixels electrically connected to the scan lines and the data lines and arranged in a plurality of rows and columns, each pixel including an OLED and a thin film transistor electrically connected to the OLED. The processor calculates a heading to a target based on a deviation from the alignment heading as measured from a heading and elevation measurement determined from the inertial measurement unit.