* The heart rate monitor displays the estimated heart rate based on the pulse measured by the sensor on the back of the watch (back cover). The heart rate data displayed by the watch is for reference only, and accuracy is not guaranteed. * The heart rate measurement function of this watch is for recreational use only and cannot be used for any medical purpose. * When without GPS signal reception or without a smartphone link, the watch operates with normal quartz accuracy (average monthly difference: ±15 seconds). * The altimeter is a relative altimeter that converts changes in pressure to altitude. When atmospheric pressure changes due to weather conditions, the measured altitude value also changes. * For outdoor temperature measurements, remove watch from wrist and make sure that it is not affected by body temperature, sweat (water droplets) or direct sunlight.