In marine 3-D surveys, the shooting direction (boat track) is considered to be the ''in-line direction'', whereas in land 3-D surveys, the receiver cable is along the in-line direction. The direction that is perpendicular to the in-line direction in a 3-D survey is called the ''cross-line direction''. In contrast to 2-D surveys in which line spacing can be as much as [[length::1 km]], the line spacing in 3-D surveys can be [[length::50 m]] or less. This dense coverage requires an accurate knowledge of shot and receiver locations. | In marine 3-D surveys, the shooting direction (boat track) is considered to be the ''in-line direction'', whereas in land 3-D surveys, the receiver cable is along the in-line direction. The direction that is perpendicular to the in-line direction in a 3-D survey is called the ''cross-line direction''. In contrast to 2-D surveys in which line spacing can be as much as [[length::1 km]], the line spacing in 3-D surveys can be [[length::50 m]] or less. This dense coverage requires an accurate knowledge of shot and receiver locations. |