Early wireless or nodal systems relied on radios to transfer data. Initially, data was transferred sequentially from each recording unit after acquisition of a record, but later systems could transfer data from multiple units in real-time. Due to their bulk, limited battery life, and limited channel count, the use of such systems was typically limited to transition zone surveys where conventional, cabled, land systems were not suitable, and the water was too shallow for a marine streamer survey. The nodes were typically mounted on floats attached to anchors with the sensors themselves placed in the water.
The first system extensively used for land acquisition was the Seismic Group Recorder or SGR introduced in the early 1980s (Shave 1982).
The SGR differed from other systems in that the data was recorded internally on tape. Development of radio systems continued through the 1990s, such systems either sent the full dataset in real-time or sent limited QC data with the full data being downloaded manually later.
The Ultra G5, which was the first to utilise continuous data recording (rather than radio triggered recording). Although it continuously recorded data it still required time synchronisation messages to be sent via radio.
The first nonradio real-time data system introduced was the VibTech (later Sercel) Unite, which used a mesh Wi-Fi system to transmit data. The first ‘blind’ (i.e. no real-time data or QC status) system was the Geospace GSR launched in 2007.
This approach was enabled by the introduction of low-cost GPS chips that enabled time synchronisation across multiple disconnected units. As with the Ultra G5, it incorporated continuous recording with the shot records being extracted or ‘combed’ based on source GPS times after the data had been manually downloaded. The system utilised a digitiser unit with separate geophone and a battery. This was the approach taken with other systems introduced until 2019 including AutoSeis, iSeis Sigma, and INOVA Hawk.
Nodal seismic Case studies
SAE METIS PROJECT
The world’s largest nodal seismic survey, with AGS and STRYDE in Oman
