1. n. [Geophysics]
A line joining base stations whose transmissions are synchronized during surveying.
2. n. [Geophysics]
A reference line, such as a "shale baseline," a line representing the typical value of a given measurement for a shale on a well log, or the zero-amplitude line of a seismic trace.
See: bias
3. n. [Geophysics]
The original survey of a set of surveys covering the same area but acquired over a period of time. In four-dimensional seismic data, it is the first seismic survey, which is then compared to subsequent surveys.