Boys start to get acne at the age of approximately 12 years, with a range of 9 to 15 years old. As most girls will attest, boys on average mature later than girls. Early on in the onset of teen acne, the main lesions are blackheads and whiteheads.
The angular size (angular diameter, apparent size) of an object as seen from a given point is the visual diameter of the object measured as an angle. The visual diameter is the diameter of the perspective projection of the object on a plane through its center that is perpendicular to the viewing direction.
Many posters of satellite images of the Earth have their pixels averaged to represent larger areas, although the original spatial resolution of the sensor that collected the imagery remains the same. Section 2.3 Spatial Resoluti on, Pixel Size, and Scale Page 39Canada Centre for Remote Sensing.