segyinput.pdf

SEG-Y Input159 SeisSpace® Tools Reference

SEG-Y Input

SEG-Y Input reads data from most disk image files approximately conforming to the SEG-Y standard, produced by various workstations including Sierra, Landmark, MS-DOS, Charisma, Prakla, and Western. It offers the additional,non-standard option, to read more than one SEG-Y file in sequence.

Usage

Traces can be grouped into ensembles by:

• FFID (File No.) bases input records on SEGY field file number. Used primarily for shot gathers.

• CDP bases input traces on their common depth point number. Used primarily for CDP gathers.

• SOURCE, SOU_XD, or SOU_YD bases input records on the sequential source number or changes in coordinates within the file. To be used primarily for shot gathers.

• REC_XD, or REC_YD bases input ensembles on changes in their receiver coordinates. Used primarily for receiver gathers.

• OFFSET bases input ensembles on changes in the offset header. Used primarily for common offset gathers.

• NONE retains default trace ensembles, as indicated by the SEG-Y header

The SEG-Y binary header can be in one of the following formats:

• IBM Real is 4-byte IBM Floating Point SEG-Y.

• IEEE Real is 4-byte IEEE Floating Point SEG-Y (non-standard).

• 4 byte Integer is 4-byte Integer SEG-Y.


• 4 byte w/Gain is 4-byte SEG-Y Fixed Point with Gain Code.

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Standard SEG-Y Header and translation to SeisSpace®

Bytes Use Input Output

1-4 trace sequence number within line

Ignored (reassigned internally in SeisSpace®)

Output from TRACENO

5-8 trace sequence number within reel

Ignored Used on output

9-12 original field record number Input to FFID Output from FFID

13-16 trace number within the original field record (channel)

Input to CHAN Output from CHAN

17-20 energy source point number Input to SOURCE Output from SOURCE

21-24 CDP ensemble number Input to CDP Output from CDP

25-28 trace number within CDP ensemble

Ignored Output from SEQNO

29-30 trace identification code Input to TRC_TYPE Output from TRC_TYPE

31-32 number of vertically summed traces

Ignored Ignored

33-34 number of horizontally stacked traces (fold)

Input to TR_FOLD Output from TR_FOLD

35-36 data use: production or test Ignored Ignored

37-40 distance from source to receiver Input to OFFSET and AOFFSET

Output from OFFSET

41-44 receiver group elevation Input to REC_ELEV Output from REC_ELEV

45-48 surface elevation at source Input to SOU_ELEV Output from SOU_ELEV

49-52 source depth below surface Input to DEPTH Output from DEPTH

53-56 datum elevation at receiver Ignored Ignored

57-60 datum elevation at source Ignored Ignored

61-64 water depth at source Input to SOU_H2OD Output from SOU_H2OD

65-68 water depth at receiver Input to REC_H2OD Output from REC_H2OD

69-70 scalar for bytes 41-68 Used on input Computed on output

71-72 scalar for bytes 73-88 Used on input Computed on output



73-76 source X coordinate Input to SOU_XD, 8 byte real

Output from SOU_XD (precise to 7 digits)

77-80 source Y coordinate Input to SOU_YD, 8 byte real

Output from SOU_YD (precise to 7 digits)

81-84 receiver X coordinate Input to REC_XD, 8 byte real

Output from REC_XD (precise to 7 digits)

85-88 receiver Y coordinate Input to REC_YD, 8 byte real

Output from REC_YD (precise to 7 digits)

89-90 coordinates units - to database Input to data context Output from data context

91-92 weathering velocity Ignored Ignored

93-94 sub-weathering velocity Ignored Ignored

95-96 uphole time at source Input to UPHOLE Output from UPHOLE

97-98 uphole time at receiver Ignored Ignored

99-100 source static correction Input to SOU_STAT Output from SOU_STAT

101-102 receiver static correction Input to REC_STAT Output from REC_STAT

103-104 total static applied Input to TOT_STAT Output from TOT_STAT

105-106 lag time A Ignored Ignored

107-108 lag time B Ignored Ignored

109-110 delay recording time Ignored Ignored

111-112 mute time start Input to TLIVE_S Output from TLIVE_S

113-114 mute time end Input to TFULL_S Output from TFULL_S

115-116 number of samples in this trace Ignored (cannot vary in SeisSpace®)

Output from data context

117-118 sample interval in this trace Ignored (cannot vary in SeisSpace®)

Output from data context

119-120 gain type of instruments Ignored Ignored

121-122 instrument gain constant Ignored Ignored

123-124 instrument early gain Ignored Ignored

125-126 correlated flag Ignored Ignored

127-128 sweep start frequency Ignored Ignored

129-130 sweep end frequency Ignored Ignored




131-132 sweep length Ignored Ignored

133-134 sweep type Ignored Ignored

135-136 sweep start taper length Ignored Ignored

137-138 sweep end taper length Ignored Ignored

139-140 sweep taper type Ignored Ignored

141-142 alias filter freq - to database Ignored Ignored

143-144 alias filter slope - to database Ignored Ignored

145-146 notch filter freq - to database Ignored Ignored

147-148 notch filter slope - to database Ignored Ignored

149-150 low cut freq - to database Ignored Ignored

151-152 high cut freq - to database Ignored Ignored

153-154 low cut slope - to database Ignored Ignored)

155-156 high cut slope - to database Ignored Ignored)

157-158 year recorded - to database Ignored Ignored

159-160 day of year recorded Ignored Ignored

161-162 hour of day recorded Ignored Ignored

163-164 minute of hour recorded Ignored Ignored

165-166 second of minute recorded Ignored Ignored

167-168 time basis code Ignored Ignored

169-170 trace weighting factor used in 32 and 16 bit integer formats

computed for 32 and 16 bit integer formats

171-172 geophone group number of roll switch pos. 1

Ignored Ignored

173-174 geophone group number of trace 1 in record

Ignored Ignored

175-176 geophone group number of last trace in record

Ignored Ignored

177-178 gap size Ignored Ignored

179-180 overtravel associated with taper Ignored Ignored

181-240 optional use Used on input Used on output




Loading non-standard SEGY headers

You can override the SEG-Y trace header, using user-supplied format and position. Header entries are created if they do not exist. Format can be 2I, 4I, 4R IBM, 4R IEEE. Position is anywhere inside the 240 byte SEG-Y trace header. You can also add or modify an override entry with the submenu for Non-standard headers.

Parameters

Do you want to enter multiple SEG-Y files?

Select Yes to enter multiple SEG-Y files.

Path to the input SEG-Y file

This appears if No to multiple SEG-Y files. Enter the fully-qualified SEG-Y filename. For example,

D\:\\data\\segy\\Synth_Shots.segy or /export/d01/SEGY/FieldRecords.sgy.

List of input SEG-Y files

This appears if Yes to multiple SEG-Y files. Click the Editor icon and enter your list of fully-qualified SEG-Y filenames. The Editor window allows cut and paste, and the import of text files. Separate individual files by spaces or by placing them on new lines. For example:

/data/Synth_Shots.segy /data/Shots2.segy

or

/data/Synth_Shots.segy /data/Shots3.segy

Print information about each input file?

Select Yes to list a data context and file size summary for each input SEG-Y file.

Output data start time

Enter the output data start time. This value can be greater than zero for delayed start time. The is used, for example, with deep water input. You can input a 1.0 s start time.



Specify input trace list?

Select Yes to specify the input trace list. Select No to use all traces.

Primary selection header

This appears if Yes to Specify input trace list. Select a primary trace header from the list of standard SeisSpace® headers.

Secondary selection header

This appears if Yes to Specify input trace list. Select a secondary trace header from the list of standard SeisSpace® headers.

Specify selection list

This appears if Yes to Specify input trace list. Enter a list to define the traces.

Since data from a file is input sequentially, you should try to build the list based upon sequential location within a file. If the primary selection choice is decreasing within the file then the list should be decreasing. For example:

100-1/

The default, *.*/, accepts all traces.

Override SEG-Y reel header?

Select Yes to explicilty set some or all of the global dataset informatino, rather than reading from the SEG-Y binary header.

Number of samples per trace

This appears if Yes to Override SEG-Y reel header. Enter the number of samples in a data trace. Enter 0 to get from SEG-Y binary header bytes 21-22.

This parameter is intended for the case when bytes 21-22 of the binary header are incorrect. The number of samples specified must represent the exact number of samples.

Note: For Sierra format, this value is required. You must enter the number of samples in the data traces.



Maximum number of traces per ensemble

This appears if Yes to Override SEG-Y reel header. Enter 0 for the default.

Input data sample interval

This appears if Yes to Override SEG-Y reel header. Enter 0 for the default.

Data is stacked?

This appears if Yes to Override SEG-Y reel header. Select Yes if the input traces are stacked data.

Input trace format?

This appears if Yes to Override SEG-Y reel header. Select the input data format, or instruct the program to read the format information from the SEG-Y binary header. The normal choice would be to read the information from the binary header, but this can be incorrect. If that happens, you will have to specify the format. The choices are:

• Get from header gets the trace format from binary header.

• IBM Real is 4-byte IBM Floating Point SEG-Y.

• IEEE Real is 4-byte IEEE Floating Point SEG-Y (non-standard).



• 4 byte w/Gain is 4-byte SEG-Y Fixed Point with Gain.

Input data primary sort order

This appears if Yes to Override SEG-Y reel header. Select how the traces are sorted on this SEG-Y tape. The choices are:

• Get from header gets the trace format from binary header.

• CDP bin number

• Source number



• Receiver index number

• Source-receiver offset

• Recording channel

• Inline number

• Crossline number

• Unknown

Load non-standard headers?

Select Yes to load non-standard headers. The Non-Standard headers menu appears. Click Show to display defined mappings. Click Add to add one or more override definitions.

Non-standard header parameters.

Click Show button to view non-standard header parameters.

Starting byte number of the non-standard header

Enter the starting byte number of the header to be mapped, counting at byte 1 of the trace header.

Format of the non-standard header

Select the input data format The choices are:



• IEEE Float is 4-byte IEEE Floating Point SEG-Y.

• IBM Float is 4-byte IBM Floating Point SEG-Y.

Output SeisSpace® header

Choose a standard SeisSpace® header from the pop-up list or enter a new one in the User defined header space above the list.

New SeisSpace® header description

This appears if a User defined header is entered for Output SeisSpace® header. Enter a new description for the SeisSpace® header. This description can contain spaces.



New SeisSpace® header format

This appears if a User defined header is entered for Output SeisSpace® header. Select one of the following SeisSpace® header formats:



• 4 byte Float is 4-byte Float SEG-Y.

• 2 byte Float is 2-byte Float SEG-Y.

End of non-standard header parameters.

Click Hide button to remove non-standard header paramters

Header used to define ensemble breaks

Select a trace header entry to use to define ensemble breaks. A new ensemble begins when the selected header value changes. Select NONE to turn this parameter off.

Expected number of output ensembles

Enter the expected number of output ensembles. Enter 0 for a computed default.

Print ensemble information?

Select Yes to print information for each output ensemble.


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