3.2.2.6. Flags

In general, flagging consists of three parts: instrument flags (on/off), telemetry flags (preliminary flagging and editing) and data quality flags (geophysical processing flags).

Telemetry flags are initially based on altimeter modes and concern checking of telemetry data quality. Only severely corrupted data are not processed. The flag setting used is designed to get a maximum of data into the Sensor Data Records. Science data are processed only when the altimeter is in a tracking mode.
Quality flags involve residuals from smoothing or fits from the data themselves. Flag setting checks for gaps, exceeded limits and excessive changes. Among these flags, some have a general meaning, describing the measurement environment.
Other flags indicate what type of surface is beneath the satellite (ocean, ice, solid earth, etc).
Instrument flags tell us which instruments are on and/or which frequencies are used (mostly for Topex/Poseidon).