The top class that provides access to geometry is TPhGeometry. Using it one can obtain quickly a pointer to a sensor or a sensor set object. This is also the place where top functions referring to global properties of the geometry can be found. TPhGeometry derives from the ROOT TGeometry class so the mechanism of geometry visualization in ROOT canvas is available and the TPhGeometry is integrated with the ROOT environment.
The TPhSensorSet class defines a group of sensors. Different sensor set types are recognized by sensor set name, class name and by user type. The class provides iterators over its sensors and subsets of sensors and also allows to find them by name. The classes derived from TPhSensorSet, specialized for a specific detector, like TPhOctagonDet may provide additional methods to retrieve sets of sensors belonging to certain parts of the detector (GetLadder, GetPhiStrip). The order of objects in the lists can be changed by sorting them according to several predefined criteria. The class overrides methods of geometrical transformations (Shift, Rotate) in order to make sure that all sensors it contains are actually connected by their nodes to the sensor set object and are thus affected by the change.
The TPhSensor class refers to a single sensor entity. Most of the geometrical properties of the sensor are reflected in the part of the class that is derived from TPhSensorNode. Additional methods providing current spatial properties of the sensor are provided by specialized classes.
Both TPhSensorSet and TPhSensor derive from TPhSensorNode class. This is an extension of the ROOT TNode class. This class provides methods for geometrical calculations not present in the TNode class or specific to Phobos requirements.