COORDINATE_SYSTEM

 The standard UMC coordinate system has its origin at the center of the apparatus. The +z axis points along the beam direction and the +y axis is vertical. Azimuthal angles are measured from the +x axis. All dimensions are in CENTIMETERS. There is also a set of auxilliary coordinate systems known as "sector coordinates." These apply to one sector at a time. The origin is still at the apparatus center and the +z direction is still along the beam, but now the y axis bisects the sector, so that, say, x=0 will be at the center of each range counter. The subroutine SECT_ROT can be used for trans- formations between the coordinate systems for cases with the standard 24- fold sector symmetry ONLY.