NAME
mgd77list - A data-extractor for <legid>.mgd77 files
SYNOPSIS
mgd77list leg-ids [ -Dastartdate ] [ -Dbstopdate ] [ -E ] [ -Fflags ] [
-H ] [ -M[flag] ] [ -N ] [ -Rwest/east/south/north ] [ -Sastartdist ] [
-Sbstopdist ] [ -V ] [ -Wweight ] [ -bo ]
DESCRIPTION
mgd77list reads <legid>.mgd77 files and produces an ASCII [or binary]
table. The <legid>.mgd77 files contain track information such as time
and position, geophysical observables such as gravity, magnetics, and
bathymetry, and control codes and corrections such as Eotvos or diurnal
corrections. The user may extract any combination of these parameters
plus the computed quantities distance, heading, and velocity (v), and
finally weight (see -W). A sub-section can be specified by passing
time- or distance-intervals along track or by selecting a region.
leg-ids
Can be one or more MGD77 8-character cruise identifiers. To give
a list of names, use ‘cat cruises.lis‘. The ".mgd77" extension
will automatically be appended, if needed. Cruise files will be
looked for in the current directory and in all directories
listed in $MGD77_DIR/MGD77_paths.txt.
OPTIONS
No space between the option flag and the associated arguments
-Da Do not list data collected before startdate (yyyy-mm-
ddT[hh:mm:ss]) [Default is start of cruise].
-Db Do not list data collected after stopdate (yyyy-mm-
ddT[hh:mm:ss]). [Default is end of cruise].
-E Exact match: Only output records that matches all the requested
geophysical columns [Default outputs records that matches at
least one of the observed columns].
-F Comma-separated list of parameter abbreviations in the desired
output order. Those parameters given in UPPER case must be
present in all output records. Unless indicated, the output for-
mat is controlled by D_FORMAT. The available abbreviations are:
id The 8-character cruise ID string
time Absolute calendar time in the format dictated by the GMT default
settings OUTPUT_DATE_FORMAT and OUTPUT_CLOCK_FORMAT.
lon Longitude in the format dictated by the GMT default OUT-
PUT_DEGREE_FORMAT.
lat Longitude in the format dictated by the GMT default OUT-
PUT_DEGREE_FORMAT.
dist Along-track distance in km or nautical miles (see -N).
mtf1 Total magnetic field intensity from sensor 1 (in nTesla).
mtf2 Total magnetic field intensity from sensor 2 (in nTesla).
mag Residual magnetic anomaly (in nTesla).
gobs Observed gravity (in mGal).
faa Free-air gravity anomaly (in mGal).
ptc Position Type Code (1 = fix, 3 = interpolated, 9 = unspecified).
bcc Bathymetric Correction Code, indicating the procedure used to
convert travel time to depth. (01-55 = Matthews’ zone - use
only if Matthews’ zones were used to correct depth, 59 =
Matthews’ corrections used but zones unspecified in data record,
60 = S. Kuwahara formula, 61 = Wilson formula, 62 = Del Grosso
formula, 63 = Carter’s tables, 88 = Other, described in header
sections, 99 = unspecified).
btc Bathymetric Type Code, indicating how the bathymetry value was
obtained (1 = observed, 3 = interpolated, 9 = unspecified).
msens Magnetic sensor for residual field (1 = 1st or leading sensor, 2
= 2nd or trailing sensor, 9 = unspecified).
msd Depth (or altitutde) of the magnetic sensor (m, positive below
sealevel).
diur Magnetic diurnal correction (nTesla).
eot Eotvos correction (mGal).
sln Seismic line number string.
sspn Seismic shot point number string.
nqc Navigation quality Code (5 = suspected, by source institution, 6
= suspected, by NGDC, 90 = no problems identified).
Logical tests may be added for any of the parameters by append-
ing one or more comma-separated instructions of the form parOP-
value, where par is one of the parameters listed above, OP is a
logical operator (<. <=, =, !=, >=, >), and value is used in the
comparison. Floating point parameters are compared numerically;
character parameters are compared lexically (after leading and
trailing blanks have been removed). At least one of the tests
must be true for the record to be output, expect for tests using
UPPER case parameters in which case the test must be true for
output to occur. Note that specifying a test does not imply that
the corresponding column will be included in the output stream;
you must specify the dataflag for that to occur.
-H Issue a header record with names for each data field.
miles; see -N)along track from port of departure. [Default is
length of track].
-V Selects verbose mode, which will send progress reports to stderr
[Default runs "silently"].
-W Set the weight for these data. Weight output option must be set
in -F. This is useful if the data are to be processed with the
weighted averaging techniques offered by blockmean, blockmedian,
and blockmode.
-bo Selects binary output mode (single precision; append d for dou-
ble precision) [Default is ASCII]. -H and -M are ignored if -bo
is selected.
EXAMPLES
To get a (distance, heading, gravity, bathymetry) listing from
01010047.mgd77, starting at June 3 1971 20:45 and ending at distance =
5000 km, use the following command:
mgd77list 01010047 -Da1971-06-03T20:45 -Sb5000 -Fdist,azim,faa,depth >
myfile.d
To make input for blockmean and surface using free-air anomalies from
all the cruises listed in the file cruises.lis, but only the data that
are inside the specified area, and make the output binary:
mgd77list ‘cat cruises.lis‘ -Flon,lat,faa -R-40/-30/25/35 -bo > all-
grav.b
To extract the locations of depths exceeding 9000 meter that were not
interpolated (btc != 1) from all the cruises listed in the file
cruises.lis:
mgd77list ‘cat cruises.lis‘ -F"depth,DEPTH>9000,BTC!=1" > really_deep.d
SEE ALSO
mgd77info(GMTMANSECTION), mgd77track(GMTMANSECTION)
REFERENCES
Wessel, P., and W. H. F. Smith, 2004, The Generic Mapping Tools (GMT)
version 4 Technical Reference & Cookbook, SOEST/NOAA.
Wessel, P., and W. H. F. Smith, 1998, New, Improved Version of Generic
Mapping Tools Released, EOS Trans., AGU, 79 (47), p. 579.
Wessel, P., and W. H. F. Smith, 1995, New Version of the Generic Map-
ping Tools Released, EOS Trans., AGU, 76 (33), p. 329.
Wessel, P., and W. H. F. Smith, 1995, New Version of the Generic Map-
ping Tools Released, http: American Geophysical Union.
Wessel, P., and W. H. F. Smith, 1991, Free Software Helps Map and Dis-
play Data, EOS Trans., AGU, 72 (41), p. 441.
GMT4.0 1 Oct 2004 MGD77LIST(GMTMANSECTION)
Man(1) output converted with
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