Processes5
Processes 5
Important SeisNav Concepts
Nav summary
Prior to a navigation file's use for merging, binning, or mapping, it must be summarized. The
summary process builds intelligence files for the software as well as the processor. The most
useful of these files is the "_summ" file, which will give maxima/minima and begin/end
acquisition values of all relevant information in the navigation file. It will also build extremity
and mean SEG Y file, which may be used to determine the details needed in the prospect
definition. The other important file built during the summary process is the "_prod" file. The
"_prod" files may be collected throughout a survey, for a final navigation production spreadsheet.
An example "_prod" file looks like the following;
START START END END TOTAL
SAILLINE SOURCE TIME SOURCE TIME SOURCE
------
85601396 2590 day 309, 13:41:36 1170 day 309, 18:02:49 822
35701456 1319 day 310, 14:50:17 2459 day 310, 18:29:05 342
22101474 1348 day 311, 04:22:03 1890 day 311, 06:05:32 543
figure 5.0 (flowgifs/summ.gif View Summary Flowchart)
Merging Marine Nav and Seismic
(See Chapter 4 for a complete description of Marine Nav files and merging them with seismic).
Merging Land Nav and Seismic
(See Chapter 4 for a complete description of Land Nav files and merging them with seismic).
Merging Transition Zone Nav and Seismic
Merging transition zone Nav and seismic is dependant on the Nav file format. If the Nav file is a
standard (contains the match for each shot) UKOOA P1/84 or P1/90, then the marine nav merge
may be used. However, if the Nav file is a non-standard UKOOA format, or either SEG P1 or
SPS, then the land Nav merge may be used. QC of source and receiver positions may be
automated by using the Residual Nav process.
Creating synthetic nav for preshoot situations
(See Chapter 9 for a complete description of creating preshoot nav files).
Checking merged Nav
The following visualization tools are available for checking a merge;
MAP Headers displays
1. Coordinate maps with bin overlay (optional ray paths)
2. FFID vs OFFSET and FFID vs FBTIME (splitscreen)
3. FFID vs SOURCE and FFID vs NSOURCE (splitscreen)
Shooting Nav displays
1. Sorted (NRECVR, NGUNFLAG, FFID)
2. Unsorted
3. Computed vs FBTIME ticks
4. FBTIME ticks vs Header Math computed ticks
2D Edit Display
1. Full shot view in land survey
2. LMO before (ticks automatically adjusted)
Building and viewing a near trace cube is also a valuable tool for examining whether or not the
navigation data matches the seismic. See merging Nav and Seismic in Chapter 4, for problem
resolution details.
Building a cube
Binning the merged seismic data must be performed. The following options are available;
1. Automatic binning during the merge when prospect is valid.
2. Process Re-Binning when it is necessary to modify your prospect.
Additional processing, such as NMO and bulk time shift, may be performed on the individual
sailline files prior to trace interpolation. Collecting individual saillines into one file using Super
Line, sorting by INLINE and XLINE using Inline Sort, and interpolating using Trace Interpolate
are the final steps.
figure 5.1 (flowgifs/bcube.gif View Cube Building Flow Chart)
Single Trace Processes
The section is designed to aid the user in adding Single Trace Processes to a job flow and
defining how they work within SeisNav.
AGC
Process Description:
Automatic Gain Control computes and applies gain scalars to each trace. One gain scalar is
computed for each sample based on the average absolute amplitude of all samples within the
AGC window. The AGC window slides down the trace one sample at a time, and one scalar is
computed for each AGC window position. The scalars are extended on the ends from the center
sample position of the first and last windows. The median of these scalars is placed in the trace
header in the GENHEAD position.
User Interface Questions:
Window Length - Length in milliseconds for the sliding window used to compute a gain scalar.
ASCII Input
Process Description:
The ASCII Input processor is an interface to a flexible tool designed to allow input of user-
customizable ASCII files. ASCII files can be used to:
CREATE a new SEG-Y headers file.
OVERWRITE the headers of an existing SEG-Y file in order.
UPDATE the headers of an existing SEG-Y file matching information within the
ASCII file.
User Interface Questions:
Input File - Select the ASCII file you wish to input.
Mode for Input - Choices are as follows;
CREATE - If this mode is selected, the processor must be the first in your control file.
The input file will be disregarded. A new SEG Y file will be created and
passed to the subsequent processors. The file will have 1 trace sample set to 0.
All headers not affected by the processor will be set to default value (usually 1
or 0). Key Headers and Data Headers are treated the same.
OVERWRITE - The headers you specify will be read from the ASCII file and will
overwrite the traces in the order they are in (one trace per ASCII record). Key
Headers and Data Headers are treated the same.
UPDATE - The headers in your SEG Y input file will be overwritten with matching
information from the ASCII Input file. If ALL the Key Headers in the SEG Y
trace match the Key Headers in an ASCII Input record, ALL the Data Headers
in the ASCII Input record will overwrite the corresponding headers in the
SEG Y file.
Delimiter for text (blank if none) - Enter a single character delimiter. This should not be
specified if the ASCII Input file is arranged in columns. An example of a comma-
delimited ',' record is as follows;
123,124,125,126,127
Consecutive Delimiters Treated as One - If you have entered a delimiter above, toggle this
question to YES if you wish to have consecutive delimiters treated as one delimiter. For example, if your file is space delimited and there can be more than one space between
fields, you would want to answer YES. Answer NO to have consecutive delimiters skip
fields. An example of each is as follows:
Answer YES for this type of format (where there are 4 numeric fields delimited
by spaces):
123 456 678 890
Answer NO for this type of format (where there are 4 numeric fields delimited
by commas ','):
123,456,678,890(field1=123, field2=456, field3=678, field4=890)
123,,234,345(field1=123, field2=0, field3=234, field4=345)
Load a Globally Saved Format - Load a previously saved format. Formats are saved in the
directory $GQCCFG/ascii_in. The current format will be replaced by the format you
choose to load.
Save a Globally Saved Format - Save the format you have currently entered. Formats are saved
in the directory $GQCCFG/ascii_in.
Format for text file - Click on SELECT to bring up a format window with the following options;
Add a Key Header - Adds a Key Header to the spreadsheet. Key Headers are the top
fields in the spreadsheet. The Bottom area also details which spreadsheet
positions are Key Headers. When adding a key header, select a header from
the list presented. The header will show up in the spreadsheet in a non-editable
field. The position information will be defaulted to 0 and must be updated.
Add a Data Header - Adds a Data Header to the spreadsheet. Data Headers are the
bottom fields in the spreadsheet. The Bottom area also details which
spreadsheet positions are Data Headers. When adding a data header, select a
header from the list presented. The header will show up in the spreadsheet in a
non-editable field. The position information will be defaulted to 0 and must be
updated.
Delete the selected row - Deletes the Data Header or Key Header that your cursor
position is currently on. The header and formatting information are deleted
from the spreadsheet and the sample area.
Spreadsheet updating for Delimited formats - The field delimiter cannot be changed
once the spreadsheet is up. To change the delimiter, close the spreadsheet,
change the delimiter, then bring the spreadsheet up again. Which Field is the
only positioning field for delimited formats. It denotes the field to be used.
The area before the delimiter is field 0. The area between delimiter 1 and
delimiter 2 is field 1, etc.
Spreadsheet updating for Non-Delimited formats - Start Offset and End Offset are the
positioning fields for non-delimited formats. Start Offset and End Offset are 1-
indexed inclusive offsets into the record denoting the start and end of the
current field.
Sample Area at bottom - The current fields that will be used according to the
spreadsheet information are annotated at the bottom of the spreadsheet in the
Sample Area. The first record of the file is read and shown. All fields that are
defined in the spreadsheet are highlighted in alternating colors. The
highlighted area is scanned and the printed value at the bottom reflects the
value that is scanned out. The sample area updates whenever you move your
cursor across fields in the spreadsheet, add a header, or delete a header.
ASCII Output
Process Description:
The ASCII Output processor is an interface to a sophisticated, flexible set of tools providing:
Customizable ASCII Output of headers
Customizable ASCII Summarizing of header data and trace data
Navigation file output
ASCII Output is unique in that it can run as part of a control file (as a single trace process) or
can terminate a control file at the end (instead of an Output file or Display). This allows
summarizing of a SEG Y file without requiring output of a new SEG Y.
User Interface Questions:
Navigation File Type - Select Not Nav for regular output. Select one of the nav types to output a
nav file (SPS, SEG P1, P1/84, P1/90)
Navigation Output File Action - The choices are as follows;
NEW FILE - create a new nav file with the given name
ADD TO FILE - add new points to the given file
UPDATE FILE - update the existing coordinates in the file
Output File Name - The file you wish to dump the ASCII Output to. If you want the output to go
to the processing log, enter a file name of NONE.
Maximum record length to output - The Maximum record length only applies to partial records.
The last record of you format is not required to have a new-line character. If it does not,
multiple records will be put on one line. If you do not enter a maximum record length,
no new-lines will be inserted in this record (except possibly by other records). If you
enter a maximum record length, the record will repeat as many times as it can before
reaching the length. At this point, a new-line will be inserted and output will continue.
The record will never be split over 2 lines. Enter a number <= 0 to have no maximum
record length. Example:
Format = '(5RSEQTR) (5FBTIME), ' (with no new-line)
Max Record Length = 45
Output = ' 1 123, 2 136, 3 141, (new-line)' (39 characters)
' 4 156, 5 167, 6 190, (new-line)'
Load a Globally Saved Format - Load a previously saved format (several are pre-installed).
Formats are saved in the directory $GQCCFG/ascii_out. The current format in the
text window will be replaced by the format you choose to load.
Save a Globally Saved Format - Save the format currently in your text area. Formats are saved
in the directory $GQCCFG/ascii_out.
Add a Header to the format - Brings up an interface window to allow building of header words to
add to format. The options are as follows;
Select Header Word to add - Select a trace header word from the list.
Summary key (required for SUMMARY RECORDS) - Select the type of
summary to use if this header will be in a SUMMARY RECORD.
Possible types are MINIMUM, MAXIMUM, FIRST, LAST,
AVERAGE, SUM, RANGE, and RMS. Also, the Breaking types can
be selected: TOP, BOTTOM, and CONSTANT. If this header is in a
regular record, select NONE.
Total Field Size (0 means variable) - If non-zero, this is the minimum size that
will be output for this field.
Total Digits after decimal point (0 means no decimal) - If non-zero, this is the
number of digits after the decimal place.
Field Justification - Choices are RIGHT Justified or LEFT Justified.
Left Justified Example: (<6FFID) = '123 '
Right Justified Example: (6FFID) = ' 123'
Click Save to add the current header information to the text area. Closing without save
deletes any changes.
Add Trace Information to the format - Almost the same as the above (Add a Header to the
format). There is no button to pick a headers word. TRACE is used instead of a header
word. The Summary key is Trace Information Type and only has the following possible
options which are required. Note that NONE is not an option here:
MINIMUM, MAXIMUM, FIRST, LAST, AVERAGE, SUM, RANGE, RMS
Text Area - This large free-format text area is the entry area for your format. Important
commands that work in the area:
'C-' means the 'Control' key 'Ctrl' on some keyboards
'C-a' go to first of line
'C-e' go to end of current line
'C-k' cut from current position to the end of the current line
'C-y' paste (yank) the previous cut (C-k) to the current position
'C-s' search forward
'C-r' search backward
'C-d' delete-right-character
'C-h' delete-left-character (if 'Backspace' and 'Delete' key do not work)
'C-l' re-center and refresh screen
'C-v' page down
Use the arrow keys to move around. If the arrow keys do not work on your keyboard,
you can use the following:
'C-n' down (Next line)
'C-b' left (Back character)
'C-p' up (Previous line)
'C-f' right (Forward character)
General Rules for ASCII Output format creation:
1) Navigation File Output - Currently only SPS nav files can be used. All of the Navigation
Output File Actions are supported for SPS.
2) Record Types for Custom Output - There are 3 record types: SUMMARY, HEADER, and
REGULAR. These types are described as follows;
HEADER: HEADER records must begin the line with an 'H' character. HEADER
records contain only text. No trace header information is allowed. HEADER
records will be output during the first trace that passes through the format. If
you wish the HEADER records to be at the top, place them at the top of your
format. If REGULAR records are in the format above the HEADER records,
the first trace's REGULAR records will be output before the HEADER records.
SUMMARY: SUMMARY records must begin the line with an 'S' character.
SUMMARY records may contain either trace header information or text. See
the rules below for entering trace header records. There are two sub-classes of
SUMMARY records (breaking and non-breaking). Non-breaking SUMMARY
records may have any of the seven types (minimum, maximum, first, last,
average, sum, and range). Their information is output whenever the file
reaches a break. After their information is output, the keys restart (i.e. new
min, max, first, last, avg, or sum). A break is automatically forced at the end of
a file. Optionally, breaking trace header words can be used.
REGULAR: REGULAR records begin with a character other that 'S' or 'H'. REGULAR
records may contain either trace header information or text. See the rules
below for entering trace header records. For each trace that passes through, the
REGULAR records are output.
3) Header Record Formatting Rules.
Header fields must be enclosed with parenthesis (i.e. '(FFID)').
All additional formatting information must precede the header word inside the
parenthesis (i.e. '(<5.1FFID)').
Specify a field size by adding a number to the field. If a field size is not specified, it is
variable. If a field size is specified and the actual field size for the current
record is smaller than your size, the field is padded. If the actual field is
bigger, it will overflow to the right. Examples:
FORMATVALUE=123VALUE=1234VALUE=12345
'(FFID)''123''1234''12345'
'(4FFID)'' 123''1234''12345'
'(6FFID)'' 123'' 1234'' 12345'
By default, the fields are right justified. To force left justification within a field, include
'<' within the field. Examples:
FORMATVALUE=123VALUE=1234VALUE=12345
'(<4FFID)''123 ''1234''12345'
'(<6FFID)''123 ''1234 ''12345 '
By default, the fields are integer fields. To force the field to be a floating point field,
include a '.' character followed by the number of decimal places you wish to
follow the decimal point. Examples:
FORMATVALUE=123VALUE=1234VALUE=12345
'(<4.1FFID)''123.0''1234.0''12345.0'
'(<6.1FFID)''123.0 ''1234.0''12345.0'
'(8.1FFID)'' 123.0'' 1234.0'' 12345.0'
4) Header word SUMMARY keys - REGULAR Trace Header keys CANNOT contain the
following keys (it will be ignored if entered). SUMMARY Trace Header keys must
contain one of the following keys:
'+' - Top Level NORMAL Breaking Key - breaks on inconsistencies in a pattern. This
allows complex 2-level patterns to be summarized (using a Bottom Level
NORMAL Breaking Key).
'-' - Bottom Level NORMAL Breaking Key - breaks on inconsistencies in a pattern.
This allows complex 2-level patterns to be summarized (using a Top Level
NORMAL Breaking Key).
'=' - CONSTANT Breaking Key - breaks whenever the key changes. This only allows
simpler 1-level patterns to be summarized (using a Bottom Level NORMAL
Breaking Key).
'a' - Minimum
'b' - Maximum
'c' - First
'd' - Last
'e' - Average
'f' - Sum
'g' - Inclusive Range = (maximum - minimum) for floating point numbers, and
= (maximum - minimum + 1) for integer numbers
'h' - RMS value (Square Root of the Mean of the Squares of the values)
5) Rules For Breaking Trace Header Words
NORMAL Breaking Key with a CONSTANT Breaking Key - The summarizing will
break whenever the CONSTANT Breaking Key changes or whenever the
NORMAL Breaking Key differs from it's pattern. Examples:
Pattern:FFID's from 1-3. Within each FFID channels range from 1-100.
FFID's from 4-6. Within each FFID channels range from 4000-5000.