1. n. [Geophysics]
A dataset measured and recorded with reference to a particular area of the Earth's surface, such as a seismic survey.
See: accelerometer, base station, baseline, baseline, benchmark, benchmark, cultural noise, depth point, drift, electromagnetic method, free-air correction, gravity, gravity survey, magnetics, monument, perpendicular offset, salt proximity survey, seismic, side-scan sonar, telluric-current method
3. n. [Drilling]
A completed measurement of the inclination and azimuth of a location in a well (typically the total depth at the time of measurement). In both directional and straight holes, the position of the well must be known with reasonable accuracy to ensure the correct wellbore path and to know its position in the event a relief well must be drilled. The measurements themselves include inclination from vertical, and the azimuth (or compass heading) of the wellbore if the direction of the path is critical. These measurements are made at discrete points in the well, and the approximate path of the wellbore computed from the discrete points. Measurement devices range from simple pendulum-like devices to complex electronic accelerometers and gyroscopes used more often as MWD becomes more popular. In simple pendulum measurements, the position of a freely hanging pendulum relative to a measurement grid (attached to the housing of the tool and assumed to represent the path of the wellbore) is captured on photographic film. The film is developed and examined when the tool is removed from the wellbore, either on wireline or the next time pipe is tripped out of the hole.
4. n. [Drilling]
A precise and legally binding measurement of surface locations, referenced to known benchmark locations.
5. vb. [Drilling]
To make the measurements as in definitions 1 or 2.
7. vb. [Formation Evaluation]
To record a measurement versus depth or time, or both, of one or more physical quantities in or around a well. In early years, the term was used more often than log.