{
  "etracl": {"byte": 1, "type": "Q","desc": "Extended trace sequence number within line"},
  "etracr": {"byte": 9, "type": "Q","desc": "Extended trace sequence number within file"},
  "efldr": {"byte": 17, "type": "q","desc": "Extended original field record number"},
  "ecdp": {"byte": 25, "type": "q","desc": "Extended nsemble number"},
  "egelev": {"byte": 33, "type": "d","desc": "Extended elevation of receiver group"},
  "gdepth": {"byte": 41, "type": "d","desc": "Extended receiver group depth"},
  "eselev": {"byte": 49, "type": "d","desc": "Extended surface elevation at source"},
  "esdepth": {"byte": 57, "type": "d","desc": "Extended source depth"},
  "egdel": {"byte": 65, "type": "d","desc": "Extended seismic datum elevation at receiver group"},
  "esdel": {"byte": 73, "type": "d","desc": "Extended seismic datum elevation at source"},
  "eswdep": {"byte": 81, "type": "d","desc": "Extended water depth at source"},
  "egwdep": {"byte": 89, "type": "d","desc": "Extended water depth at receiver group"},
  "esx": {"byte": 97, "type": "d","desc": "Extended source coodinate x"},
  "esy": {"byte": 105, "type": "d","desc": "Extended source coordinate y"},
  "egx": {"byte": 113, "type": "d","desc": "Extended group coordinate x"},
  "egy": {"byte": 121, "type": "d","desc": "Extended group coordinate y"},
  "eoffset": {"byte": 129, "type": "d","desc": "Extended offset"},
  "ens": {"byte": 137, "type": "I","desc": "Extended number of samples"},
  "secfrac": {"byte": 141, "type": "i","desc": "Nanoseconds to add to second of minute"},
  "edt": {"byte": 145, "type": "d","desc": "Extended sample interval"},
  "cable": {"byte": 153, "type": "i","desc": "Cable number"},
  "nthe": {"byte": 157, "type": "H","desc": "Number of additional trace headers"},
  "lasttr": {"byte": 159, "type": "h","desc": "Last trace flag"},
  "ecdpx": {"byte": 161, "type": "d","desc": "Extended x-coordinate of ensemble"},
  "ecdpy": {"byte": 169, "type": "d","desc": "Extended y-coordinate of ensemble"},
  "reserved1": {"byte": 177, "type": "d","desc": "Reserved1"},
  "reserved2": {"byte": 185, "type": "d","desc": "Reserved2"},
  "reserved3": {"byte": 193, "type": "d","desc": "Reserved3"},
  "reserved4": {"byte": 201, "type": "d","desc": "Reserved4"},
  "reserved5": {"byte": 209, "type": "d","desc": "Reserved5"},
  "reserved6": {"byte": 217, "type": "d","desc": "Reserved6"},
  "reserved7": {"byte": 225, "type": "d","desc": "Reserved7"},
  "unassigned1": {"byte": 233, "type": "q","desc": "SEG00001, ASCII or EBCDIC"}
}
