CGG (formerly CGGVeritas) works by land and by sea to provide seismographic services and equipment for oil companies worldwide. Its geophysical services units provide land-based seismic surveying, including borehole services, and marine seismic surveying. The company can mobilize an average of 19 land and transition zone crews, and it operates a fleet of more than 20 marine vessels. It also processes the seismic data it collects. Its Sercel unit makes geophysical equipment, including land and marine seismic acquisition systems. CGG's land unit uses vibroseismic vehicles (as well as explosives and airguns) to generate acoustical waves, which are captured by geophones and converted into digital data.