/* $Id: segy.h 12822 2014-01-31 23:39:56Z remko $ */ #pragma once #ifndef SEGY_H #define SEGY_H /* This is the header for the PASSCAL SEGY trace data. * From PASSCAL code base which is in the public domain * http://www.passcal.nmt.edu/ * * The PASSCAL SEGY trace format is a modified form of the SEG-Y * trace format. The modification comes is because we use some of * the unspecified header words to store information pertinent to * the PASSCAL data. The data values for each trace are preceded * by a 240 byte header. This format is given below. All integer * values are stored with the most significant byte first. Data * values are either 16 0r 32 bit integers depending on byte 206 * of the header, the field named "data_form". * * Up to byte 180, the definitions follow the SEGY definition laid down * by Barry et al. * * Reading bytes directly into this header will allow access to * all of the fields. The number in the comment is the byte offset * into the segy file. An "X" in the comment indicates that field * is NEVER set. Fields that are set to default values contain that * value and follow a ":" in the comment ("grep : segy.h" will spit * all default fields out). Two pairs of fields exist to cover an * inherited limitation; sampleLength/num_samps and deltaSample/samp_rate. * When the value is too large to fit in a int16_t, sampleLength or * deltaSample become flags and require their int32_t counterparts, * num_samps and samp_rate, to contain that value. * * Edit F. Wobbe: use unsigned types for values that are known to be positive */ typedef struct SegyHead { /* Offset Description */ int32_t lineSeq; /* 0 Sequence numbers within line */ int32_t reelSeq; /* 4 Sequence numbers within reel */ int32_t event_number; /* 8 Original field record number or trigger number */ int32_t channel_number; /* 12 Trace channel number within the original field record */ int32_t energySourcePt; /* 16 X */ int32_t cdpEns; /* 20 X */ int32_t traceInEnsemble; /* 24 X */ int16_t traceID; /* 28 Trace identification code: seismic data = 1 */ int16_t vertSum; /* 30 X */ int16_t horSum; /* 32 X */ int16_t dataUse; /* 34 X */ int32_t sourceToRecDist; /* 36 X */ int32_t recElevation; /* 40 X */ int32_t sourceSurfaceElevation; /* 44 X */ int32_t sourceDepth; /* 48 X */ int32_t datumElevRec; /* 52 X */ int32_t datumElemSource; /* 56 X */ int32_t recWaterDepth; /* 60 X */ int32_t sourceWaterDepth; /* 64 X */ int16_t elevationScale; /* 68 Elevation Scaler: scale = 1 */ int16_t coordScale; /* 70 Coordinate Scaler: scale = 1 */ int32_t sourceLongOrX; /* 72 X */ int32_t sourceLatOrY; /* 76 X */ int32_t recLongOrX; /* 80 X */ int32_t recLatOrY; /* 84 X */ int16_t coordUnits; /* 88 Coordinate Units: = 2 (Lat/Long) */ int16_t weatheringVelocity;/* 90 X */ int16_t subWeatheringVelocity; /* 92 X */ int16_t sourceUpholeTime; /* 94 X */ int16_t recUpholeTime; /* 96 X */ int16_t sourceStaticCor; /* 98 X */ int16_t recStaticCor; /* 100 X */ int16_t totalStatic; /* 102 Total Static in MILLISECS added to Trace Start Time */ int16_t lagTimeA; /* 104 X */ int16_t lagTimeB; /* 106 X */ int16_t delay; /* 108 X */ int16_t muteStart; /* 110 X */ int16_t muteEnd; /* 112 X */ uint16_t sampleLength; /* 114 Number of samples in this trace (unless == 0xffff) */ uint16_t deltaSample; /* 116 Sampling interval in MICROSECONDS (unless == 1) */ int16_t gainType; /* 118 Gain Type: 1 = Fixed Gain */ int16_t gainConst; /* 120 Gain of amplifier */ int16_t initialGain; /* 122 X */ int16_t correlated; /* 124 X */ int16_t sweepStart; /* 126 X */ int16_t sweepEnd; /* 128 X */ int16_t sweepLength; /* 130 X */ int16_t sweepType; /* 132 X */ int16_t sweepTaperAtStart; /* 134 X */ int16_t sweepTaperAtEnd; /* 136 X */ int16_t taperType; /* 138 X */ int16_t aliasFreq; /* 140 X */ int16_t aliasSlope; /* 142 X */ int16_t notchFreq; /* 144 X */ int16_t notchSlope; /* 146 X */ int16_t lowCutFreq; /* 148 X */ int16_t hiCutFreq; /* 150 X */ int16_t lowCutSlope; /* 152 X */ int16_t hiCutSlope; /* 154 X */ int16_t year; /* 156 year of Start of trace */ int16_t day; /* 158 day of year at Start of trace */ int16_t hour; /* 160 hour of day at Start of trace */ int16_t minute; /* 162 minute of hour at Start of trace */ int16_t second; /* 164 second of minute at Start of trace */ int16_t timeBasisCode; /* 166 Time basis code: 2 = GMT */ int16_t traceWeightingFactor; /* 168 X */ int16_t phoneRollPos1; /* 170 X */ int16_t phoneFirstTrace; /* 172 X */ int16_t phoneLastTrace; /* 174 X */ int16_t gapSize; /* 176 X */ int16_t taperOvertravel; /* 178 X */ char station_name[6]; /* 180 Station Name code (5 chars + \0) */ char sensor_serial[8]; /* 186 Sensor Serial code (7 chars + \0) */ char channel_name[4]; /* 194 Channel Name code (3 chars + \0) */ char extrash[2]; /* 198 Extra unassigned bytes (2 chars) */ uint32_t samp_rate; /* 200 Sample interval in MICROSECS as a 32 bit integer */ int16_t data_form; /* 204 Data Format flag: 0=16 bit, 1=32 bit integer */ int16_t m_secs; /* 206 MILLISECONDS of seconds of Start of trace */ int16_t trigyear; /* 208 year of Trigger time */ int16_t trigday; /* 210 day of year at Trigger time */ int16_t trighour; /* 212 hour of day at Trigger time */ int16_t trigminute; /* 214 minute of hour at Trigger time */ int16_t trigsecond; /* 216 second of minute at Trigger time */ int16_t trigmills; /* 218 MILLISECONDS of seconds of Trigger time */ float scale_fac; /* 220 Scale Factor (IEEE 32 bit float) */ uint16_t inst_no; /* 224 Instrument Serial Number */ int16_t not_to_be_used; /* 226 X */ uint32_t num_samps; /* 228 Number of Samples as a 32 bit integer */ int32_t max; /* 232 Maximum value in Counts */ int32_t min; /* 236 Minimum value in Counts */ } SEGYHEAD; /* end of segy trace header */ #endif /* !SEGY_H */