Observed / Expected Observations
The percentage corresponds, for each constellation tracked by the station, to the ratio of the number of observations in the daily RINEX file with respect to the number of expected observations:
- 1f   : all observations are counted.
- 2+f : only observations on at least two frequencies are counted. These are the observations usable for geodetic positioning.
The horizontal black dotted line (log ele) indicates the elevation cut off angle provided by the station manager in the station site log file (available from M3G). The lowest elevation cut off observed in the RINEX data is indicated in purple (obs ele). In theory "log ele" and "obs ele" should agree. Differences can be caused by degraded tracking at low elevations (obstructions or erroneous GNSS equipment) or by an incorrect elevation cut off angle in the station site log.
Red vertical lines, green and blue vertical dotted lines indicate respectively a change of antenna, receiver or receiver configuration (including firmware) as indicated by the station manager in the station site log available from the M3G GNSS Metadata Catalog. The purple points in the top of the plot indicate the daily RINEX data availability at the data node.