An image forming apparatus is provided in which, by detecting an image formed on a recording medium, at least one of the density and chromaticity of the image can be properly controlled. The microprocessor may be configured to execute at least one of a base-band encoder software program or a base-band decoder software program. The mounting portion defines a mounting aperture that extends from the first major surface to the second major surface, and is configured to receive a hammer mounting pin. Additionally, decoded data associated with the position of interest can be presented to an operator of a surveying tool. An armature is free-floating with respect to the needle member. The correlation error is compared with a predetermined correlation error value.