Quality control slang for a series that stops changing: the sensor repeats the same reading because it is jammed, out of the water at low tide, iced over, or the logger is resending a stale value. Automated checks flag flatlines alongside spikes and rate-of-change limits. A gauge that flatlines only at low water usually has its sensor or orifice mounted too high.
Gauge flatlines at minus 0.4 on every spring low, the orifice is sitting out of the water.
Also heard as
- flat-lined data
- stuck sensor
Related terms
Six-minute data
Water level values recorded every six minutes, the standard sampling interval at many tide stations.
Tide gauge
An instrument that records water level continuously at a fixed point, the basic tool of tidal measurement.
Bubbler
Field name for a gas-purge pressure gauge that measures water level by pushing gas through an underwater orifice.
Residual
The observed water level minus the predicted tide, showing the effect of weather, rivers and other non-tidal causes.