Version 1.00
Lynx TracePrep uses the Trace Auxiliary File (TAX) file format to store and retrieve trace file auxiliary or header information in easily accessible ASCII form. The TAX file acts as an intermediary for storing information which would otherwise have to be held in a variety of auxiliary file types, as in Lynx's MS-DOS based 3S software. The information within the TAX file can easily be edited by Lynx's TaxEdit program, which contains import faciliities for older 3S file types, or by any text editor such as Windows Notepad.
A TAX file contains information relating to an individual seismic trace file or profile. It will usually have the same name as the corresponding trace file, but with the extension .TAX. The information in the TAX file may in some cases be related to existing trace header information, or it may be auxiliary data which relates to the trace file but cannot be stored in trace headers, e.g. velocities or horizon picks.
The TAX file is an ASCII file, which uses the familiar INI file layout and contains one or more sections, each preceded by a section name enclosed in square brackets, e.g. [sectionname]. For example, the optional [lynx] section contains general information about the file, version number, comments etc.
Individual items within a section are of the form
key=value
where key is a string or numeric identifier, unique within a section. A key may contain one or more elements, separated by comma delimiters. key is often used to represent a location on the profile.
value is the alphanumeric information attributed to
key. Value is a single numeric or text item or may be a comma
delimited list containing more than one item, separated by commas.
Other nomenclature used in the descriptions of standard section types below :-
nnnn is an integer number
ffff is a floating point number
ssss is a text string
tttt is a time in milliseconds
uuuu is a distance units indicator, feet or metres. Where distances are in traces, CDPs, or shotpoints they are dimensionless. When in LatLon, units are decimal degrees.
pppp is a position along the profile (represented by the corresponding trace file), in units determined by the xunits and coordtype keys. pppp may be either integer, or floating point
coordtype is a coordinate type, distance, CDP, Latlon, shotpoint or trace, for the parameter describing the position of a point on the seismic profile. Actual locations on the Earth's surface are related to this parameter by data in the [location] section.
Compound keys are used when there is a possibility that the same location may apply to more than one value, e.g. velocity control point data. In this case, the key will contain a qualifier after the position part, e.g.
pppp,q=value
3-D data are also accomodated by keys having two elements, e.g.
crossline,inline=value where crossline is the profile number and inline is the coordinate (trace number etc.) within a profile.
IMPORTANT NOTES
1) Unlike a standard Windows-style INI file, the keys in a TAX file can be non-unique within a section. This enables handling of data such as velocities, which can have multiple values for a given trace or shotpoint.
2) Elements within key and value fields are separated by comma delimiters. Text containing commas should be enclosed in double quotation marks e.g. "text, which contains a comma". Floating point numbers should use the full stop character as a separator and the use of commas to separate the thousands in large numbers should be avoided.
The [global] section contains keys and values which may apply to all sections in the file
name=ssss
where ssss is the line name of the seismic profile to which this TAX file is attached
coordtype=coordtype
where coordtype can be trace, shotpoint CDP or distance. This determines whether positions pppp are trace, CDP or shotpoint positions, or distances along the actual profile on the ground.
xyunits=uuuu
where units are the units in which horizontal distances are measured.. (Default metres) The x and y (distance) units used in the rest of the file. Distance units can be mixed within the file, i.e. an individual sections can contain its own local units key.
zunits=zzzz and
tunits=tttt similarly hold the units
for vertical two way time and depth.
[mute] section
The mute section contains one or more records of the form
xxxx=tttt1,tttt2
where xxxx is the position along the profile and tttt1 and tttt2 are the corresponding mute start and end times at that position. If no coordtype key is present in the [global] section, the default is for xxxx to be a trace number and for tttt a time in milliseconds
[shotpoint] section contains the shotpoint to trace relationship, two or more records of the form
pppp=ffff
where pppp is a position (see coordtype global key) and ffff is the corresponding shotpoint number. If the coordtype for the file is shotpoint, the existing shotpoints will be renumbered.
[label]
The label section contains text information which can be
inserted into the headers of individual traces in a seismic file (Lynx file
fomats only) for displaying trace related information such as line
intersections.
pppp=ssss
Horizons are interpreted points, lines or surfaces on the corresponding seismic section corresponding to known geological or stratigraphic interfaces or other surfaces of interest to interpreters or processors. Picks are points on a horizon, in the vertical plane of the seismic profile, characterised by a surface coordinate (shotpoint, trace cdp etc.) and a time or depth.
[horizon]
The horizon names section contains a list of names for the
horizons, of the form
hname=description
where hname is a key name uniquely identifying the horizon and description is a short description. If the named horizon has any associated data (picks), an individually named sections corresponding to specific horizons.
hname cannot be identical to other reserved words used in trace auxiliary files.
[hz_hname]
Each individual horizon is given a unique section
called hz_hname. Within the section, the horizon picks appear as points
in the form
pppp,rrrr,ffff=tttt,zzzz
where pppp are the numeric positions along the profile, q is a qualifier, e.g. record number and tttt are the corresponding time or depth values at that position. If no coordtype key is present in the [global] section, the default is for pppp to be a trace number.
rrrr is a record number, determining the ordering of the points
ffff is an optional fault or termination flag, e.g.begin, end, or the name of fault or horizon, defining terminatoion, pinchout, subcrop, downlap etc. This provides separators, which split the horizon into segments., where it discontinuous or faulted. If the horizon has only one segment, no flags are necessary. If ffff is not present, the preceding comma may be omitted.
tttt is time in units according to the tunits keyword.
zzzz is depth in units according to the zunits keyword .
colour=cccc where cccc is a colour index enables a display colour to be associated with a horizon.
(not implemented) A side label is a panel on the side of a seismic section display where information about the profile, survey, acquisition, processing and other cultural data are displayed.
[velocity] section
Velocities are used by various programs in the TPMig package.
pppp,q=tttt,vvvv
where pppp,q is a unique record number pppp represents a location on the profile (shotpoint, trace, CDP or distance) and q is a qualifier, e.g. record number to make the key unique. The coordtype value in the [global] section of the TAX file will determine what type of position is used. Note that 3-S velocity files only have the option of coordtype as trace or shotpoint. Location by shotpoint presupposes that correct shot point numbers have been entered in the trace headers. Location by trace should be used with care if the profile is split, merged or resampled, because the trace numbering will be altered in those cases.
tttt,vvvv is a time, rms velocity pair at the location pppp. Times are in milliseconds, velocities in feet or metres per second, depending on the xunits key in the [global] section. Note that velocities are assumed to be stacking (or rms) velocities. For example, a section with 2 velocity functions, at traces 1 and 250, each having four points might look like :-
1,1=0,1480
1,2=275,1480
1,3=2048,2900
1,4=3000,3400
1,5=5000,4500
250,1=0,1480
250,2=325,1480
250,3=2900,3400
250,4=5000,4500
[location] section
XY locations are used by the XYCOORD process in the TPUtil package, for inserting and extracting trace locations from trace headers. The location section contains two or more points of the form
pppp=xxxx,yyyy
where pppp represents a position on a profile (shotpoint, trace etc.) and xxxx,yyyy the corresponding coordinates on the Earth's surface in geographical coordinates, or some local rectangular coordinate system. Note that there will normally be at least two entries in the location section, corresponding to two points near each end of the profile
Certain section names and keys are reserved, i.e. they can only be used for a specific purposes and not as general identifiers for keys or sections.
| reserved word | identifies |
| global | section |
| coordtype | key |
| horizon | section |
| mute | section |
| shotpoint | section |
| tunits | key |
| velocity | section |
| xyunits | key |
| zunits | key |