Precipitable water vapor (PWV) strongly affects the quality of data obtained
from millimeter- and submillimeter-wave astronomical observations, such as
those for cosmic microwave background (CMB) measurements. Some of these
observatories have used radiometers to monitor PWV. In this study, PWV was
measured from April 2021 to April 2022 using Global Navigation Satellite System
(GNSS) instruments in the Atacama Desert, Chile, where several millimeter and
submillimeter-wave telescopes are located. We evaluated the accuracy of these
measurements by comparing them to radiometer measurements. We calculated the
PWV from GNSS data using Canadian Spatial Reference System Precise Point
Positioning (CSRS-PPP), an online software package. When using GNSS data alone,
the estimated PWV showed a systematic offset of +1.08 mm. When combining GNSS
data with data from a barometer which was co-located with the GNSS receiver,
the estimated PWV showed a lower systematic offset of -0.14 mm. The GNSS PWV
showed a statistical error of 0.52 mm with an averaging time of an hour.
Compared to other PWV measurement methods, GNSS instruments are robust in bad
weather conditions, have sufficient time resolution, and are less expensive. By
demonstrating good accuracy and precision in low PWV conditions, this paper
shows that GNSS instruments are valuable tools for PWV measurements for
observing site evaluation and data analysis for ground-based telescopes