To estimate latitude and direction he had to be fiercely observant in daylight, too.

为了估计纬度和方向，克雷默得在白天保持极其敏锐的观察力。

When the birds flew south for the winter, the geolocator tags regularly recorded the light levels and the time, allowing the scientists to estimate each bird's approximate latitude and longitude.

当鸟儿飞往南方过冬时，地理定位标签会定期记录光照水平和时间，使科学家能够估计每只鸟的大致纬度和经度。