Method and device for determining the squareness of an ice skate blade. According to one embodiment, the device may include an electrode stator and a reading unit. The reading unit may be mechanically coupled to a carriage. The carriage, in turn, may be slidably mounted on a pair of posts for translational movement. A master roller may be disposed at one end of the carriage, and the carriage may be biased in the direction of the master roller. The electrode stator may be mechanically coupled to a plunger. The plunger, in turn, may be slidably mounted on the carriage for translational movement along the same axis as the carriage; however, the plunger may be capable of moving independently of the carriage. A slave roller may be disposed at one end of the plunger, and the plunger may be biased in the direction of the slave roller.

Described herein are methods and systems for determining a relative position of different portions of a hinged device. Motion sensor data from sensor assemblies of each portion is fused to relate the device portions to a world frame. An angular orientation between the device portions is determined with respect to the hinge axis and accumulating sensor measurement errors are compensated by constraining determined axes of the sensor assemblies using the motion sensor data and known relationships between physical axes of the sensor assemblies and the mechanical hinge, such that the determined axes of the sensor assemblies are aligned along the hinge axis.

Described herein are methods and systems for determining a relative position of different portions of a hinged device. Motion sensor data from sensor assemblies of each portion is fused to relate the device portions to a world frame. An angular orientation between the device portions is determined with respect to the hinge axis and accumulating sensor measurement errors are compensated by constraining determined axes of the sensor assemblies using the motion sensor data and known relationships between physical axes of the sensor assemblies and the mechanical hinge, such that the determined axes of the sensor assemblies are aligned along the hinge axis.