NOVELTY - The apparatus has a GPS receiver and a motion sensor. A control logic obtains GPS data from the GPS receiver and obtains data from the motion sensor. The control logic determines step count data from the data obtained from the one motion sensor. The control logic determines first refined data for first measurement intervals using the temporally-corresponding and independently-measured GPS data and the step count data. The control logic converts the GPS data into a multiple sequential first measurements.    USE - Biometric monitoring device worn on body of person (claimed) or insertable into wearable case such as wristband, belt-clip, pendant and exercise equipment e.g. bicycle, weight-lifting tracker, sit-up reps tracker, pull up reps tracker, golf swing analyzer, etc, used for tracking sleep quality, waking period, sleep latency, sleep efficiency, sleep stages of user, heart rate, pH level, hydration level, respiration rate and other physiological metrics.    ADVANTAGE - The signal-to-noise ratio is enhanced or optimize and the power consumption by the light sources and light detectors is reduced or minimized. Since a sustained contact is provided between the biometric monitoring device and the skin of user, relative motion between the biometric monitoring device and the user is decreased and thus the quality of the cardiac signal of interest is increased. The exterior surface of the biometric monitoring device is provided with a vent type configuration thus ambient air is allowed to move in and out of the housing of the device and water and other liquids are prevented from flowing into the device. The weight lifting apparatus is enabled to automatically lift the weight or to prevent the lowering of weight when the user approaches failure limit.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) a method for GPS accuracy refinement; and    (2) a non-transitory, machine-readable storage medium storing program for GPS accuracy refinement.    DESCRIPTION OF DRAWING(S) - The drawing shows a perspective view of the portable monitoring device.