/usr/share/doc/gmt/html/man/mgd77list.html is in gmt-doc 4.5.12-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 | <!-- Creator : groff version 1.22.2 -->
<!-- CreationDate: Thu Feb 27 18:14:42 2014 -->
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta name="generator" content="groff -Thtml, see www.gnu.org">
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
<meta name="Content-Style" content="text/css">
<style type="text/css">
p { margin-top: 0; margin-bottom: 0; vertical-align: top }
pre { margin-top: 0; margin-bottom: 0; vertical-align: top }
table { margin-top: 0; margin-bottom: 0; vertical-align: top }
h1 { text-align: center }
</style>
<title>MGD77LIST</title>
</head>
<body bgcolor="#ffffff">
<h1 align="center">MGD77LIST</h1>
<a href="#NAME">NAME</a><br>
<a href="#SYNOPSIS">SYNOPSIS</a><br>
<a href="#DESCRIPTION">DESCRIPTION</a><br>
<a href="#OPTIONS">OPTIONS</a><br>
<a href="#EXAMPLES">EXAMPLES</a><br>
<a href="#RECALCULATED ANOMALIES">RECALCULATED ANOMALIES</a><br>
<a href="#IGRF">IGRF</a><br>
<a href="#IGF">IGF</a><br>
<a href="#CORRECTIONS">CORRECTIONS</a><br>
<a href="#QUALITY CODES">QUALITY CODES</a><br>
<a href="#SEE ALSO">SEE ALSO</a><br>
<a href="#REFERENCES">REFERENCES</a><br>
<hr>
<h2>NAME
<a name="NAME"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">mgd77list
− A data-extractor for MGD77[+] files</p>
<h2>SYNOPSIS
<a name="SYNOPSIS"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em"><b>mgd77list</b>
<i>NGDC-ids</i>
<b>−F</b><i>columns</i>[,<i>logic</i>][:<i>bittests</i>]
[
<b>−A</b>[<b>+</b>]<b>c</b>|<b>d</b>|<b>f</b>|<b>m</b>|<b>t</b><i>code</i>
] [ <b>−Cf</b>|<b>g</b>|<b>e</b> ] [
<b>−DA</b>|<b>a</b><i>startdate</i> ] [
<b>−DB</b>|<b>b</b><i>stopdate</i> ] [ <b>−E</b>
] [ <b>−Ga</b><i>startrec</i> ] [
<b>−Gb</b><i>stoprec</i> ] [
<b>−H</b>[<b>i</b>][<i>nrec</i>] ] [
<b>−I</b><i>ignore</i> ] [
<b>−L</b>[<i>corrtable</i>] ] [
<b>−Nd</b>|<b>s</b><i>unit</i> ] [
<b>−Qa</b>|<b>v</b><i>min</i>/<i>max</i> ] [
<b>−R</b><i>west</i>/<i>east</i>/<i>south</i>/<i>north</i>[<b>r</b>]
] [ <b>−Sa</b><i>startdist</i>[unit] ] [
<b>−Sb</b><i>stopdist</i>[unit] ] [
<b>−T</b>[<b>m</b>|<b>e</b>] ] [ <b>−V</b> ] [
<b>−W</b><i>weight</i> ] [
<b>−Z</b><i>+</i>|<b>-</b> ] [
<b>−bo</b>[<b>s</b>|<b>S</b>|<b>d</b>|<b>D</b>[<i>ncol</i>]|<b>c</b>[<i>var1</i><b>/</b><i>...</i>]]
] [ <b>−m</b>[<i>flag</i>] ]</p>
<h2>DESCRIPTION
<a name="DESCRIPTION"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em"><b>mgd77list</b>
reads <NGDC-id>.[mgd77|nc] files and produces an ASCII
[or binary] table. The <NGDC-id>.[mgd77|nc] files
contain track information such as leg-id, time and position,
geophysical observables such as gravity, magnetics, and
bathymetry, and control codes and corrections such as Eotvos
and diurnal corrections. The MGD77+ extended netCDF files
may also contain additional user columns (for a listing of
available columns, use <b>mgd77info −C</b>, and to
learn how to add your own custom columns, see
<b><A HREF="mgd77manage.html">mgd77manage</A></b>). The user may extract any combination of
these parameters, any of six computed quantities (distance,
heading, velocity, Carter correction, and gravity and
magnetic global reference fields), calendar sub-units of
time (year, month, day, hour, min, sec), the NGDC id, and
finally a preset weight (see <b>−W</b>). A sub-section
can be specified by passing time- or distance-intervals
along track or by selecting a geographical region. Finally,
each output record may be required to pass any number of
logical tests involving data values or bit flags. <i><br>
NGDC-ids</i></p>
<p style="margin-left:22%;">Can be one or more of five
kinds of specifiers: <br>
1) 8-character NGDC IDs, e.g., 01010083, JA010010etc., etc.
<br>
2) 2-character <agency> codes which will return all
cruises from each agency. <br>
3) 4-character <agency><vessel> codes, which
will return all cruises from those vessels. <br>
4) =<list>, where <list> is a table with NGDC
IDs, one per line. <br>
5) If nothing is specified we return all cruises in the data
base. <br>
(See mgd77info <b>−L</b> for agency and vessel codes).
The ".mgd77" or ".nc" extensions will
automatically be appended, if needed (use <b>−I</b> to
ignore certain file types). Cruise files will be looked for
first in the current directory and second in all directories
listed in <b>$MGD77_HOME</b>/mgd77_paths.txt [If
<b>$MGD77_HOME</b> is not set it will default to
<b>$GMT_SHAREDIR</b>/mgd77].</p>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>−F</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>The required <i>columns</i> string must be a
comma-separated list of parameter abbreviations given in the
desired output order. Any parameters given in UPPER case
must not be NaN in a record for output to occur. Unless
specified separately, the output format (if ASCII) is
controlled by the GMT parameter <b><A HREF="gmtdefaults.html#D_FORMAT">D_FORMAT</A></b>. The
available abbreviations are:</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>drt</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>The digital record type, usually 3 or 5 (for
Y2K-compliant cruises).</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>id</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>The survey ID string (leg name).</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>tz</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>The time zone adjustment (in hours from -13 to +12)</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>ngdcid</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>The 8-character NGDC cruise ID string (usually the file
prefix).</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>time</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>Choose between Absolute calendar time (<b>atime</b>, the
default) in the format dictated by the GMT parameters
<b><A HREF="gmtdefaults.html#OUTPUT_DATE_FORMAT">OUTPUT_DATE_FORMAT</A></b> and <b><A HREF="gmtdefaults.html#OUTPUT_CLOCK_FORMAT">OUTPUT_CLOCK_FORMAT</A></b>,
Relative time (<b>rtime</b>) in the format dictated by the
GMT parameters <b><A HREF="gmtdefaults.html#D_FORMAT">D_FORMAT</A></b> and <b><A HREF="gmtdefaults.html#TIME_SYSTEM">TIME_SYSTEM</A></b> (or
<b><A HREF="gmtdefaults.html#TIME_EPOCH">TIME_EPOCH</A></b> and <b><A HREF="gmtdefaults.html#TIME_UNIT">TIME_UNIT</A></b>)), or Fractional year
(<b>ytime</b>) in the format dictated by
<b><A HREF="gmtdefaults.html#D_FORMAT">D_FORMAT</A></b>.</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>lon</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>Longitude in the format dictated by the GMT parameter
<b><A HREF="gmtdefaults.html#OUTPUT_DEGREE_FORMAT">OUTPUT_DEGREE_FORMAT</A></b>.</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>lat</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>Longitude in the format dictated by the GMT parameter
<b><A HREF="gmtdefaults.html#OUTPUT_DEGREE_FORMAT">OUTPUT_DEGREE_FORMAT</A></b>.</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>twt</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>Two-Way Travel time (in s).</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>depth</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>Corrected bathymetry (in m, positive below
sealevel).</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>mtf1</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>Magnetic Total Field intensity from sensor 1 (in
nTesla).</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>mtf2</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>Magnetic Total Field intensity from sensor 2 (in
nTesla).</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>mag</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>Residual magnetic anomaly (in nTesla).</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>gobs</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>Observed gravity (in mGal).</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>faa</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>Free-air gravity anomaly (in mGal).</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>ptc</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>Position Type Code (1 = fix, 3 = interpolated, 9 =
unspecified).</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>bcc</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>Bathymetric Correction Code, indicating the procedure
used to convert travel time to depth. (01-55 =
Matthews’ zone used to correct the depth, 59 =
Matthews’ corrections used but the zones is
unspecified in the data record, 60 = S. Kuwahara formula for
T-S, 61 = Wilson formula for T-S, 62 = Del Grosso formula
for T-S, 63 = Carter’s tables, 88 = Other, described
in header sections, 99 = unspecified).</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>btc</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>Bathymetric Type Code, indicating how the bathymetry
value was obtained (1 = observed, 3 = interpolated, 9 =
unspecified).</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>msens</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>Magnetic sensor for used to evaluate the residual field
(1 = 1st or leading sensor, 2 = 2nd or trailing sensor, 9 =
unspecified).</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>msd</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>Depth (or altitude) of the magnetic sensor (in m,
positive below sealevel).</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>diur</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>Magnetic diurnal correction (in nTesla).</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>eot</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>Eotvos correction (in mGal).</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>sln</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>Seismic Line Number string.</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>sspn</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>Seismic Shot Point Number string.</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>nqc</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>Navigation Quality Code (5 = suspected, by source
institution, 6 = suspected, by NGDC, 9 = no problems
identified).</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>bqc</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>Bathymetry Quality Code (1 = good, 2 = fair, 3 = poor, 4
= bad, 5 = bad, suspected by source institution, 6 = bad,
suspected by NGDC, 9 = not set).</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>mqc</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>Magnetics Quality Code (1 = good, 2 = fair, 3 = poor, 4
= bad, 5 = bad, suspected by source institution, 6 = bad,
suspected by NGDC, 9 = not set).</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>gqc</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>Gravity Quality Code (1 = good, 2 = fair, 3 = poor, 4 =
bad, 5 = bad, suspected by source institution, 6 = bad,
suspected by NGDC, 9 = not set).</p></td></tr>
</table>
<p style="margin-left:22%; margin-top: 1em">In addition,
the following derived quantities can be requested:</p>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p style="margin-top: 1em"><b>year</b></p></td>
<td width="2%"></td>
<td width="78%">
<p style="margin-top: 1em">The year of each record.</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>month</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>The month of each record.</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>day</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>The day of the month of each record.</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>hour</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>The hour of each record.</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>min</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>The minutes of each record.</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>sec</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>The decimal seconds of each record.</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>date</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>The date in yyyymmdd string format.</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>hhmm</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>The clock in hhmm.xxxx format (0-2359.xxxx).</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>dmin</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>The decimal minutes of each record (0-59.xxxx).</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>dist</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>Along-track distance from start of leg. For method of
calculation, see <b>−C</b> [spherical great circle
distances], and for distance units, see <b>−N</b>
[km].</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>az</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>Ship azimuth (heading) measured clockwise from north (in
degrees).</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>vel</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>Ship speed; see <b>−N</b> for units [m/s].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>weight</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>Weight assigned to this data set (see
<b>−W</b>).</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>carter</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>Carter depth correction, if <b>twt</b> is present in
file (in m). Sign: Correction is to be subtracted from
uncorrected depths to yield a corrected depth.</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>igrf</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>International geomagnetic reference field (total field)
(in nTesla).</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>ngrav</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>International Gravity reference Field ("normal
gravity") (in mGal). Field is selected based on the
parameter Gravity Theoretical Formula Code in the
cruise’s MGD77 header. If this is not set or is
invalid we default to the IGF 1980. Alternatively, specify
the field directly using <b>−Af</b> (see that option
for more details).</p></td></tr>
</table>
<p style="margin-left:22%; margin-top: 1em">The following
short-hand flags are also recognized:</p>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p style="margin-top: 1em"><b>mgd77</b></p></td>
<td width="2%"></td>
<td width="78%">
<p style="margin-top: 1em">This results in all 27 MGD77
fields being written out in the official MGD77 order.</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>mgd77t</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>This results in all 26 MGD77T fields being written out
in the official MGD77T order.</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>all</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>as mgd77 or mgd77t but time is written as a single
date-time string.</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p><b>geo</b></p></td>
<td width="2%"></td>
<td width="78%">
<p>This limits the output to 10 fields (<b>time</b>,
<b>lon</b>, <b>lat</b> plus the seven geophysical
observations <b>twt</b>, <b>depth</b>, <b>mtf1</b>,
<b>mtf2</b>, <b>mag</b>, <b>gobs</b>, and <b>faa</b>). By
appending <b>+</b> to either of these set we will also
append <b>dist</b>, <b>azim</b>, <b>vel</b>, and
<b>weight</b> as listed above.</p></td></tr>
</table>
<p style="margin-left:22%; margin-top: 1em">As an option,
logical tests may be added for any of the observations by
appending ,<i>logic</i>, which is itself composed of one or
more comma-separated instructions of the form
<i>par</i><b>OP</b><i>value</i>, where <i>par</i> is one of
the parameters listed above, <b>OP</b> is a logical operator
(<, <=, =, !=, >=, >, |), and <i>value</i> is a
constant used in the comparison. Floating point parameters
are compared numerically; character parameters are compared
lexically (after leading and trailing blanks have been
removed). The bit comparison (|) means that at least one of
the bits in <i>value</i> must be turned on in <i>par</i>. At
least one of the tests must be true for the record to be
output, except for tests using UPPER case parameters which
all 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; it must be present in
<i>columns</i> for that to occur. Note: some of the
operators are special UNIX characters and you are advised to
place quotes around the entire argument to
<b>−F</b>.</p>
<p style="margin-left:22%; margin-top: 1em">Finally, for
MGD77+ files you may optionally append :<i>bittests</i>
which is : (a colon) followed by one or more comma-separated
+-<i>col</i> terms. This compares specific bitflags only for
each listed column. Here, + means the chosen bit must be 1
(ON) whereas - means it must be 0 (OFF). All bit tests given
must be passed. By default, MGD77+ files that have the
special <b>MGD77_flags</b> column present will use those
flags, and observations associated with ON-bits (meaning
they are flagged as bad) will be set to NaN; append : with
no trailing information to turn this behavior off (i.e., no
bit flags will be consulted).</p>
<h2>OPTIONS
<a name="OPTIONS"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">No space
between the option flag and the associated arguments.</p>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em"><b>−A</b></p></td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em">By default, corrected depth
(<b>depth</b>), magnetic residual anomaly (<b>mag</b>),
free-air gravity anomaly (<b>faa</b>), and the derived
quantity Carter depth correction (<b>carter</b>) are all
output as is (if selected in <b>−F</b>); this option
adjusts that behavior. For each of these columns there are
2−4 ways to adjust the data. Append <b>c</b>(arter),
<b>d</b>(epth), <b>f</b>(aa), or <b>m</b>(ag) and select the
<i>code</i> for the procedure you want applied. You may
select more than one procedure for a data column by summing
their numerical <i>code</i>s (1, 2, 4, and 8). E.g.,
<b>−Ac</b> 3 will first try method <b>−Ac</b> 1
to estimate a Carter correction but if <b>depth</b> is NaN
we will next try <b>−Ac</b> 2 which only uses
<b>twt</b>. In all cases, if any of the values required by
an adjustment procedure is NaN then the result will be NaN.
This is also true if the original anomaly is NaN. Specify
<b>−A+</b> to recalculate anomalies even if the
anomaly in the file is NaN. Additionally, you can use
<b>−At</b> to create fake times for cruises that has
no time; these are based on distances and cruise
duration.</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−Ac</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Determines how the <b>carter</b> correction term is
calculated. Below, C(<b>twt</b>) stands for the
Carter-corrected depth (it also depends on <b>lon</b>,
<b>lat</b>), U(<b>twt</b>, <i>v</i>) is the uncorrected
depth (= <b>twt</b> * <i>v</i> / 2) using as <i>v</i> the
"Assumed Sound Velocity" parameter in the MGD77
header (if it is a valid velocity, otherwise we default to
1500 m/s); alternatively, append your preferred velocity
<i>v</i> in m/s, TU(<b>depth</b>, <i>v</i>) is the 2-way
travel time estimated from the (presumably) uncorrected
<b>depth</b>, and TC(<b>depth</b>) is the 2-way travel time
obtained by inverting the (presumably) corrected
<b>depth</b> using the Carter correction formula. Select
from</p> </td></tr>
</table>
<p style="margin-left:22%;"><b>−Ac1</b>[,<i>v</i>]
returns difference between U(<b>twt</b>, <i>v</i>) and
<b>depth</b> [Default]. <b><br>
−Ac2</b>[,<i>v</i>] returns difference between
U(<b>twt</b>, <i>v</i>) and Carter (<b>twt</b>). <b><br>
−Ac4</b>[,<i>v</i>] returns difference between
(assumed uncorrected) <b>depth</b> and Carter
(TU(<b>depth</b>)). <b><br>
−Ac8</b>[,<i>v</i>] returns difference between
U(TC(<b>depth</b>), <i>v</i>) and <b>depth</b>.</p>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em"><b>−Ad</b></p></td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em">Determines how the <b>depth</b>
column output is obtained:</p></td></tr>
</table>
<p style="margin-left:22%;"><b>−Ad1</b> returns
<b>depth</b> as stored in the data set [Default]. <b><br>
−Ad2</b>[,<i>v</i>] returns calculated uncorrected
depth U(<b>twt</b>, <i>v</i>). <b><br>
−Ad4</b> returns calculated corrected depth
C(<b>twt</b>).</p>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em"><b>−Af</b></p></td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em">Determines how the <b>faa</b>
column output is obtained. If <b>ngrav</b> (i.e., the
International Gravity reference Field (IGF), or "normal
gravity") is required it is selected based on the MGD77
header parameter "Theoretical Gravity Formula
Code"; if this code is not present or is invalid we
default to 4. Alternatively, append the preferred
<i>field</i> (1−4) to select 1 (Heiskanen 1924), 2
(IGF 1930), 3 (IGF 1967) or 4 (IGF 1980). Select from</p></td></tr>
</table>
<p style="margin-left:22%;"><b>−Af1</b>[,<i>field</i>]
returns <b>faa</b> as stored in the data set [Default].
Optionally, sets the IGF <i>field</i> to use if you also
have requested <b>ngrav</b> as an output column in
<b>−F</b>. <b><br>
−Af2</b>[,<i>field</i>] returns the difference between
<b>gobs</b> and <b>ngrav</b> (with optional <i>field</i>
directive). <b><br>
−Af3</b>[,<i>field</i>] returns the combination of
<b>gobs</b> + <b>eot</b> - <b>ngrav</b> (with optional
<i>field</i> directive).</p>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em"><b>−Am</b></p></td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em">Determines how the <b>mag</b>
column output is obtained. There may be one or two total
field measurements in the file (<b>mtf1</b> and
<b>mtf2</b>), and the column <b>msens</b> may state which
one is the leading sensor (1 or 2; it may also be
undefined). Select from</p></td></tr>
</table>
<p style="margin-left:22%;"><b>−Am1</b> returns
<b>mag</b> as stored in the data set [Default]. <b><br>
−Am2</b> returns the difference between <b>mgfx</b>
and <b>igrf</b>, where <b>x</b> is the leading sensor
(<b>1</b> or <b>2</b>) indicated by the <b>msens</b> data
field (defaults to <b>1</b> if unspecified). <b><br>
−Am4</b> returns the difference between <b>mgfx</b>
and <b>igrf</b>, where <b>x</b> is the sensor (<b>2</b> or
<b>1</b>) <i>not</i> indicated by the <b>msens</b> data
field (defaults to <b>2</b> if unspecified).</p>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p style="margin-top: 1em"><b>−C</b></p></td>
<td width="8%"></td>
<td width="78%">
<p style="margin-top: 1em">Append a one-letter code to
select the procedure for along-track distance calculation
(see <b>−N</b> for selecting units):</p></td></tr>
</table>
<p style="margin-left:22%;"><b>f</b> Flat Earth distances.
<b><br>
g</b> Great circle distances [Default]. <b><br>
e</b> Geodesic distances on current GMT ellipsoid.</p>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em"><b>−Da</b></p></td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em">Do not list data collected
before <i>startdate</i> (yyyy-mm-dd<b>T</b>[hh:mm:ss])
[Default is start of cruise]. Use <b>−DA</b> to
exclude records whose time is undefined (i.e., NaN).
[Default reports those records].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−Db</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Do not list data collected on or after <i>stopdate</i>
(yyyy-mm-dd<b>T</b>[hh:mm:ss]). [Default is end of cruise].
Use <b>−DB</b> to exclude records whose time is
undefined (i.e., NaN). [Default reports those records].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−E</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Exact match: Only output records that match all the
requested geophysical columns [Default outputs records that
matches at least one of the observed columns].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−Ga</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Do not list records before <i>startrec</i> [Default is
0, the first record].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−Gb</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Do not list data after <i>stoprec</i>. [Default is the
last record].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−H</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Issue a header record with names for each data
field.</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−I</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Ignore certain data file formats from consideration.
Append <b>a|c|m|t</b> to ignore MGD77 ASCII, MGD77+ netCDF,
MGD77T ASCII or plain tab-separated ASCII table files,
respectively. The option may be repeated to ignore more than
one format. [Default ignores none].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−L</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Apply optimal corrections to columns where such
corrections are available. Append the correction table to
use [Default uses the correction table mgd77_corrections.txt
in the <b>$MGD77_HOME</b> directory]. For the format of this
file, see CORRECTIONS below.</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−N</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Append <b>d</b> for distance or <b>s</b> for speed, then
give the desired <i>unit</i> as <b>e</b> (meter or m/s),
<b>k</b> (km or km/hr), <b>m</b> (miles or miles/hr), or
<b>n</b> (nautical miles or knots). [Default is
<b>−Ndk −Nse</b> (km and m/s)].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−Qa</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Specify an accepted range (<i>min</i>/<i>max</i>) of
azimuths. Records whose track azimuth falls outside this
range are ignored [0-360].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−Qv</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Specify an accepted range (<i>min</i>/<i>max</i>; or
just <i>min</i> if there is no upper limit) of velocities.
Records whose track speed falls outside this range are
ignored [0-infinity].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−R</b></p></td>
<td width="7%"></td>
<td width="78%">
<p><i>west, east, south,</i> and <i>north</i> specify the
Region of interest, and you may specify them in decimal
degrees or in [+-]dd:mm[:ss.xxx][W|E|S|N] format. Append
<b>r</b> if lower left and upper right map coordinates are
given instead of w/e/s/n. The two shorthands
<b>−Rg</b> and <b>−Rd</b> stand for global
domain (0/360 and -180/+180 in longitude respectively, with
-90/+90 in latitude). Alternatively, specify the name of an
existing grid file and the <b>−R</b> settings (and
grid spacing, if applicable) are copied from the grid.</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−Sa</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Do not list data that are less than <i>startdist</i>
meter along track from port of departure. Append <b>k</b>
for km, <b>m</b> for miles, or <b>n</b> for nautical miles
[Default is 0 meters].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−Sb</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Do not list data that are <i>stopdist</i> or more meters
along track from port of departure. Append <b>k</b> for km,
<b>m</b> for miles, or <b>n</b> for nautical miles [Default
is end of track].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−T</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Turns OFF the otherwise automatic adjustment of values
based on correction terms that are stored in the MGD77+ file
and used to counteract such things as wrong units used by
the source institution when creating the original MGD77 file
from which the MGD77+ file derives (the option has no effect
on plain MGD77 ASCII files). Append <b>m</b> or <b>e</b> to
limit the option to the MGD77 or extended columns set only
[Default applies to both].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−V</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Selects verbose mode, which will send progress reports
to stderr [Default runs "silently"].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−W</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Set the weight for these data. Weight output option must
be set in <b>−F</b>. This is useful if the data are to
be processed with the weighted averaging techniques offered
by <b><A HREF="blockmean.html">blockmean</A></b>, <b><A HREF="blockmedian.html">blockmedian</A></b>, and
<b><A HREF="blockmode.html">blockmode</A></b> [1].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−Z</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Append the sign you want for <b>depth</b>,
<b>carter</b>, and <b>msd</b> values below sea level
(<b>−Z-</b> gives negative bathymetry) [Default is
positive down].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−bo</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Selects binary output mode (single precision; append
<b>d</b> for double precision, or use <b>S</b>|<b>D</b> to
swap bytes on output) [Default is ASCII]. <b>−H</b> is
ignored if <b>−bo</b> is selected. Likewise,
string-fields cannot be selected. Note that if time is one
of the binary output columns it will be stored as Unix-time
(seconds since 1970). To read this information in GMT to
obtain absolute calendar time will require you to use
--TIME_SYSTEM=unix.</p> </td></tr>
</table>
<p style="margin-left:11%;"><b>−m</b>[<i>flag</i>]</p>
<p style="margin-left:22%;">Issue a multi-segment header
record with cruise ID for each cruise.</p>
<h2>EXAMPLES
<a name="EXAMPLES"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">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:</p>
<p style="margin-left:11%; margin-top: 1em"><b>mgd77list</b>
01010047 <b>−Da</b> 1971-06-03T20:45 <b>−Sb</b>
5000 <b>−F</b> dist,azim,faa,depth > myfile.d</p>
<p style="margin-left:11%; margin-top: 1em">To make input
for <b><A HREF="blockmean.html">blockmean</A></b> and <b><A HREF="surface.html">surface</A></b> 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:</p>
<p style="margin-left:11%; margin-top: 1em"><b>mgd77list</b>
‘cat cruises.lis‘ <b>−F</b> lon,lat,faa
<b>−R</b>-40/-30/25/35 <b>−bo</b> >
allgrav.b</p>
<p style="margin-left:11%; margin-top: 1em">To extract the
locations of depths exceeding 9000 meter that were not
interpolated (<b>btc</b> != 1) from all the cruises listed
in the file cruises.lis:</p>
<p style="margin-left:11%; margin-top: 1em"><b>mgd77list</b>
‘cat cruises.lis‘
<b>−F</b>"depth,DEPTH>9000,BTC!=1" >
really_deep.d</p>
<p style="margin-left:11%; margin-top: 1em">To extract
dist, faa, and grav12_2 from records whose depths are
shallower than 3 km and where none of the requested fields
are NaN, from all the MGD77+ netCDF files whose cruise ids
are listed in the file cruises.lis, we try</p>
<p style="margin-left:11%; margin-top: 1em"><b>mgd77list</b>
‘cat cruises.lis‘ <b>−E −Ia
−F</b>"dist,faa,grav12_2,depth<3000" >
shallow_grav.d</p>
<p style="margin-left:11%; margin-top: 1em">To extract
dist, faa, and grav12_2 from all the MGD77+ netCDF files
whose cruise ids are listed in the file cruises.lis, but
only retrieve records whose bitflag for faa indicates BAD
values, we try</p>
<p style="margin-left:11%; margin-top: 1em"><b>mgd77list</b>
‘cat cruises.lis‘ <b>−E −Ia
−F</b>"dist,faa,grav12_2:+faa" >
bad_grav.d</p>
<p style="margin-left:11%; margin-top: 1em">To output lon,
lat, mag, and faa from all the cruises listed in the file
cruises.lis, but recalculate the two residuals based on the
latest reference fields, try:</p>
<p style="margin-left:11%; margin-top: 1em"><b>mgd77list</b>
‘cat cruises.lis‘ <b>−F</b>
lon,lat,mag,faa <b>−Af</b> 2,4 <b>−Am</b> 2 >
data.d</p>
<h2>RECALCULATED ANOMALIES
<a name="RECALCULATED ANOMALIES"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">When
recalculated anomalies are requested (either explicitly via
the <b>−A</b> option or implicitly via E77 metadata in
the MGD77+ file) we only do so for the records whose
original anomaly was not a NaN. This restriction is
implemented since many anomaly columns contains corrections,
usually in the form of hand-edited changes, that cannot be
duplicated from the corresponding observation.</p>
<h2>IGRF
<a name="IGRF"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">The IGRF
calculations are based on a Fortran program written by Susan
Macmillan, British Geological Survey, translated to C via
f2c by Joaquim Luis, U Algarve, and adapted to GMT-style by
Paul Wessel.</p>
<h2>IGF
<a name="IGF"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">The equations
used are reproduced here using coefficients extracted
directly from the source code (let us know if you find
errors): <br>
(1) g = 978052.0 * [1 + 0.005285 * sin^2(lat) - 7e-6 *
sin^2(2*lat) + 27e-6 * cos^2(lat) * cos^2(lon-18)] <br>
(2) g = 978049.0 * [1 + 0.0052884 * sin^2(lat) - 0.0000059 *
sin^2(2*lat)] <br>
(3) g = 978031.846 * [1 + 0.0053024 * sin^2(lat) - 0.0000058
* sin^2(2*lat)] <br>
(4) g = 978032.67714 * [(1 + 0.00193185138639 * sin^2(lat))
/ sqrt (1 - 0.00669437999013 * sin^2(lat))]</p>
<h2>CORRECTIONS
<a name="CORRECTIONS"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">The correction
table is an ASCII file with coefficients and parameters
needed to carry out corrections. Comment records beginning
with # are allowed. All correction records are of the
form</p>
<p style="margin-left:11%; margin-top: 1em"><i>cruiseID
observation correction</i></p>
<p style="margin-left:11%; margin-top: 1em">where
<i>cruiseID</i> is a NGDC prefix, <i>observation</i> is one
of the abbreviations for geophysical observations listed
under <b>−F</b> above, and <i>correction</i> consists
of one or more <i>term</i>s that will be summed up and then
<b>subtracted</b> from the observation before output. Each
<i>term</i> must have this exact syntax:</p>
<p style="margin-left:11%; margin-top: 1em"><i>factor</i>[*[<i>function</i>]([<i>scale</i>](<i>abbrev</i>[-<i>origin</i>]))[^<i>power</i>]]</p>
<p style="margin-left:11%; margin-top: 1em">where terms in
brackets are optional (the brackets themselves are not used
but regular parentheses must be used as indicated). No
spaces are allowed except between <i>term</i>s. The
<i>factor</i> is the amplitude of the basis function, while
the optional <i>function</i> can be one of sin, cos, or exp.
The optional <i>scale</i> and <i>origin</i> can be used to
translate the argument (before giving it to the optional
function). The argument <i>abbrev</i> is one of the
abbreviations for observations listed above. If
<i>origin</i> is given as <b>T</b> it means that we should
replace it with the value of <i>abbrev</i> for the very
first record in the file (this is usually only done for
<i>time</i>). If the first record entry is NaN we revert
<i>origin</i> to zero. Optionally, raise the entire
expression to the given <i>power</i>, before multiplying by
the amplitude. The following is an example of fictitious
corrections to the cruise 99999999, implying the
<b>depth</b> should have the Carter correction removed,
<b>faa</b> should have a linear trend removed, the magnetic
anomaly (<b>mag</b>) should be corrected by a strange
dependency on ship heading and latitude, and <b>gob</b>s
needs to have 10 mGal added (hence given as -10):</p>
<p style="margin-left:11%; margin-top: 1em">99999999 depth
1.0*((carter)) <br>
99999999 faa 14.1 1e-5*((time-T)) <br>
99999999 mag 0.5*cos(0.5*(azim-19))^2
1.0*exp(-1e-3(lat))^1.5 <br>
99999999 gobs -10</p>
<h2>QUALITY CODES
<a name="QUALITY CODES"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">The MGD77T
format added three quality codes for bathymetry
(<b>bqc</b>), magnetics (<b>mqc</b>), and gravity
(<b>gqc</b>). They are not present in the original MGD77
format, and if requested will return 9 or NULL.</p>
<h2>SEE ALSO
<a name="SEE ALSO"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em"><i><A HREF="mgd77convert.html">mgd77convert</A></i>(1),
<i><A HREF="mgd77info.html">mgd77info</A></i>(1), <i><A HREF="mgd77manage.html">mgd77manage</A></i>(1),
<i><A HREF="mgd77track.html">mgd77track</A></i>(1)</p>
<h2>REFERENCES
<a name="REFERENCES"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">Wessel, P., and
W. H. F. Smith, 2014, The Generic Mapping Tools (GMT)
version 4.5.12 Technical Reference & Cookbook,
SOEST/NOAA. <br>
Wessel, P., and W. H. F. Smith, 1998, New, Improved Version
of Generic Mapping Tools Released, EOS Trans., AGU, 79 (47),
p. 579. <br>
Wessel, P., and W. H. F. Smith, 1995, New Version of the
Generic Mapping Tools Released, EOS Trans., AGU, 76 (33), p.
329. <br>
Wessel, P., and W. H. F. Smith, 1995, New Version of the
Generic Mapping Tools Released,
http://www.agu.org/eos_elec/95154e.html, Copyright 1995 by
the American Geophysical Union. <br>
Wessel, P., and W. H. F. Smith, 1991, Free Software Helps
Map and Display Data, EOS Trans., AGU, 72 (41), p. 441. <br>
The Marine Geophysical Data Exchange Format -
"MGD77", see
<i>http://www.ngdc.noaa.gov/mgg/dat/geodas/docs/mgd77.txt</i>
<br>
IGRF, see
<i>http://www.ngdc.noaa.gov/IAGA/vmod/igrf.html</i></p>
<hr>
</body>
</html>
|