Byte Numbers

Header Value Description

1 - 4  

Trace sequence number within line.

5 - 8  

Trace sequence number within file (reel)

9 - 12  

Original field record number

13 - 16  

Trace number within original field record

17 - 20  

Energy source point number.

21 - 24  

CDP ensemble number.

25 - 28  

Trace number within the CDP ensemble.

29 - 30  

Trace identification code: 1 = seismic data

31 - 32  

Number of vertically summed traces yielding this trace

33 - 34  

Number of horizontally stacked traces yielding this trace

35 - 36  

Data use: 1 = production 2 = test

37 - 40  

Distance from source point to receiver group.

41 - 44  

Receiver group elevation - above sea level are positive, below sea level are   negative.

45 - 48  

Surface elevation at source.

49 - 52  

Source depth below surface (positive number).

53 - 56  

Datum elevation at receiver group.

57 - 60  

Datum elevation at source.

61 - 64  

Water depth at source (this is the Fish depth below the sea surface in meters*10)

65 - 68  

Water depth at group.

69 - 70  

Scalar to be applied to all elevations & depths, specified in bytes 41 - 68 to give the real value. Scalar = 1, +/-10, +/-100, +/-1000, or +/-10,000. If positive, scalar is used as a multiplier; if negative, scalar is used as a divisor.

71 - 72  

Scalar to be applied to all coordinate specified in bytes 73 - 88 to give the real value. Scalar = 1, +/-10, +/-100, +/-1000, or +/-10,000. If  positive, scalar is used as a multiplier; if negative, scalar is used as a divisor.

73 - 76  

Source coordinate - X. UTM Easting coordinate with fish "layback" correction

77 - 80  

Source coordinate - Y. UTM Northing coordinate with fish "layback" correction

81 - 84  

Group coordinate - X. UTM Easting coordinate with fish "layback" correction

85 - 88  

Group coordinate - Y. UTM Northing coordinate with fish "layback" correction

89 - 90  

Coordinate units: 1 = length (meters or feet) 2 = seconds of arc

91 - 92  

weathering velocity.

93 - 94  

Subweathering velocity.

95 - 96  

Uphole time at source.

97 - 98  

Uphole time at group.

99 - 100  

Source static correction.

101 - 102  

Group static correction.

103 - 104  

Total static applied.

105 - 106  

Lag time A. Time in ms between end of 240-byte trace identification header  and time break. positive if time break occurs after end of header, negative if time break occurs before end of header. Time break is defined as the initiation pulse which may be recorded on an auxiliary trace or as otherwise specified by the recording system.

107 - 108  

Lag time B. Time in ms between the time break and positive or negative.

109 - 110  

Delay recording time. Time in ms between initiation time of energy source and  time when recording of data samples begins.

111 - 112  

Mute time - start.

113 - 114  

Mute time - end.

115 - 116  

Number of samples in this trace.

117 - 118  

Sample interval, in microseconds, for this trace.

119 - 120  

Gain type of field instruments: 1 = fixed, 2 = binary, 3 = floating point, 4 = ---  N = optional use

121 - 122  

Instrument gain constant.

123 - 124  

Instrument early or initial gain (db).

125 - 126  

Correlated: 1 = no 2 = yes

127 - 128  

Sweep frequency at start.

129 - 130  

Sweep frequency at end.

131 - 132  

Sweep length, ms.

133 - 134  

Sweep type: 1 = linear 2 = parabolic 3 = exponential 4 = other

135 - 136  

Sweep trace taper length at start, ms.

137 - 138  

Sweep trace taper length at end, ms.

139 - 140  

Taper type: 1 = linear 2 = cos 3 = other

141 - 142  

Alias filter frequency.

143 - 144  

Alias filter slope.

145 - 146  

Notch filter frequency.

147 - 148  

Notch filter slope.

149 - 150  

Low cut frequency.

151 - 152  

High cut frequency.

153 - 154  

Low cut slope.

155 - 156  

High cut slope.

157 - 158  

Year data recorded.

159 - 160  

Day of year.

161 - 162  

Hour of day (24 hour clock).

163 - 164  

Minute of hour.

165 - 166  

Second of minute.

167 - 168  

Time basis code: 1 = local 2 = GMT 3 = other

169 - 170  

Trace weighting factor - defined as 2-N volts for the least significant bit. (N=0,  1,...,32,767)

171 - 172  

Geophone group number of roll switch position one.

173 - 174  

Geophone group number of trace number one within original field record.

175 - 176  

Geophone group number of last trace within original field record.

177 - 178  

Gape size (total number of groups dropped).

179 - 180  

Overtravel associated with taper at beginning or end of line: 1 = down (or behind) 2 = up (or ahead)

181 - 184

Floating point fish depth (meters) from fish pressure depth