4 NAVIGATION



4.1 Navigation Overview - Susan Merle and Bill Chadwick

All ROPOS dives were navigated using long-baseline transponder nets with the Seascape navigation software. The navigation computer had three main inputs into Seascape to aid in ROPOS navigation: P-code GPS from the R/V Thomas Thompson, ROV depth data provided by the ROPOS sensor and the PS8000 data from the range meter. Transponders were already in place for the ASHES net and the North Rift Zone (NRZ) net. Deployed last year during NeMO'98, the expendable transponders should have five year lifetimes. The transponders for those two nets only needed to be enabled. A third net, on the South Rift Zone (SRZ), was added with three recoverable transponders. Unfortunately, due to hardware problems with the NOAA PS-8000, the calibration of the SRZ Net was poor and this net was only marginally useful.



Once the cage reached its final depth and ROPOS drove to the seafloor, the cage depth was manually entered into the Seascape program and was held constant, unless the wire out for the cage changed during the dive. The range meter was attached to the top of the cage, was hard-wired to the hydro lab and triggered by Seascape on the navigation computer. Cage and ROV fixes were generally scattered with RMS errors of about 30 meters. Navigation fixes are recorded in latitude/longitude and UTM x/y (in meters) in the log files and were processed by Susan Merle in the IDL programs navedit2 and navedit3 (written by Bill Chadwick).



In 1999 navigation was somewhat less reliable than in 1998. During several dives the 11.0 transponder in the ASHES net was accidentally disabled and this caused the 1999 navigation fixes to be shifted to the west or south of the 1998. Since '98 navigation was more robust, no old vent or marker positions were changed, even if the '99 positions did not agree with those of '98. After the '99 cruise a few of the mysterious navigation problems we had were identified. The NOAA PS-8000 on El Guapo was determined to have a bad microprocessor, which created problems with the SRZ net calibration. Another mystery solved concerned the fact that it seemed that transponder 11.0 in the ASHES net would shut itself off. It was discovered on Bill Chadwick's Cleft cruise in September '99 that the 11.0 had a disable code of C, not B like all the other transponders. This would not have been a problem, if the ROPOS transponder we tried to use, unsuccessfully, had not had an enable code of C. So, we would try to enable the ROPOS transponder, unwittingly disabling the 11.0 transponder in the ASHES net.



The dive plots will be a useful guide to determine navigation gaps, bad navigation, etc. When acoustic nav was not available GPS ship nav was used. Plotted positions are for the reference point, about 37 meters forward of the stern at the GPS antennae.



4.2 FINAL CALIBRATED TRANSPONDER POSITIONS



North Rift Net

Transponder UTM-X (m) UTM-Y (m) Latitude Longitude Depth
9.5 420814.65 5098603.9 46° 02.1857' 130° 01.3988' 1433.9
10.5 422722.92 5097596.31 46° 01.6548' 129° 59.9096' 1395.43
8.0 420055.52 5095969.44 46° 00.7580' 130° 01.9608' 1377.93
7.5 422074.85 5094971.24 46° 00.2330' 130° 00.3862' 1294.46


ASHES Net

Transponder UTM-X (m) UTM-Y (m) Latitude Longitude Depth
11.5 424283.25 5087181.51 45° 56.0418' 129° 58.6011' 1305.4
10.5 424221.58 5084426.79 45° 54.5540' 129° 58.6227' 1340.36
9.5 422490.35 5086188.55 45° 55.4937' 129° 59.9789' 1324.67
11.0 422556.72 5088014.47 45° 56.4800' 129° 59.9453' 1330.85


South Rift Net

Transponder UTM-X (m) UTM-Y (m) Latitude Longitude Depth
10.0 423771 5084021 4554.33 ' 12958.968 ' 1471.69
8.5 421721 5082432 4553.46 ' 1300.54 ' 1401.68
12.5 422134 5084021 4554.324 ' 1300.234 ' 1492.90


4.3 VENTS AND MARKERS LOCATION TABLE
 Vents/Markers Area Longitude Latitude UTM X UTM Y Depth
 Bag City SRZ -129.98926 45.91622 423284 5085214 1534
Bob NRZ -130.01283 46.03892 421629.2 5098870.2 1590
Castle North SRZ -129.97990 45.92613 424022.7 5086305.8 1520
Circ North SRZ -129.98165 45.92592 423887 5086283  
Cloud North SRZ -129.98156 45.93335 423904 5087110 1524
Coquille North SRZ -129.99306 45.91753 422991 5085365  
Crack ASHES -130.01355 45.93330 421424 5087135 1547
Crevice SRZ -129.99040 45.91110 423175 5084648 1538
Dave's ASHES -130.01377 45.93352 421408.3 5087158.6  
Dying North SRZ -129.99185 45.91685 423083.7 5085286.4  
Easy North SRZ -129.98472 45.94533 423676.5 5088443.2 1532
Fe-Hyde ASHES -130.01378 45.93298 421406 5087099.7  
Gollum ASHES -130.01358 45.93358 421422 5087166.1 1546
Hairdo ASHES -130.01398 45.93350 421390.7 5087156.8 1546
Hell ASHES -130.01423 45.93330 421372 5087135 1544
Hillock/Phoenix ASHES -130.01398 45.93325 421390.9 5087130.4 1544
Inferno ASHES -130.01390 45.93355 421397.2 5087162.2 1547
Joystick SRZ -129.98856 45.91884 423341.5 5085505  
Joystick2 SRZ -129.98851 45.91875 423345 5085495  
Magnesia North SRZ -129.98493 45.94623 423660.7 5088544.7 1530
Marshmallow ASHES -130.01362 45.93370 421420.4 5087179 1547
Medusa ASHES -130.01393 45.93335 421394.7 5087141.1 1546
Milky North SRZ -129.98475 45.94514 423673 5088424 1527
Minisnow North SRZ -129.98422 45.94262 423711 5088141 1522
Mkr-I ASHES -130.01367 45.93370 421416 5087180  
Mkr-108 Vent North SRZ -129.98303 45.92865 423784 5086589 1520
Mkr-108b Vent North SRZ -129.98319 45.92881 423772 5086608 1520
Mkr-113 Vent North SRZ -129.98827 45.92260 423370 5085922 1524
Mkr-2 ASHES -130.01397 45.93330 421392 5087136  
Mkr-21 ASHES -130.01358 45.93360 421422 5087168  
Mkr-33 Vent North SRZ -129.98225 45.93327 423850.3 5087101.1 1524
Mkr-36 SRZ -129.98161 45.93437 423284 5085214  
Mkr-42 Joystick -129.98856 45.91884 423341.5 5085505  
Mkr-D ASHES -130.01393 45.93325 421399 5087129  
Mkr-L ASHES -130.01432 45.93333 421365 5087140  
Mkr-N1 North SRZ -129.98408 45.93980 423718 5087828 1521
Mkr-N2 North SRZ -129.98475 45.94514 423673 5088424  
Mkr-N3 North SRZ -129.98520 45.94380 423637 5088278  
Mkr-N4 North SRZ -129.98167 45.93342 423896 5087119 1523
Mkr-N41 North SRZ -129.98138 45.93622 423922.4 5087428.2 1520
Mkr-N44 North SRZ -129.98483 45.93947 423658 5087792  
Mkr-N5 (Flattop) North SRZ -129.97960 45.92610 424043 5086306 1516
Mkr-N6 North SRZ -129.98160 45.93340 423901.4 5087116 1524
Mkr-N7 North SRZ -129.98190 45.93930 423886 5087774 1520
Mkr-N8 North SRZ -129.98190 45.93320 423877 5087088  
Mkr-N9 North SRZ -129.98423 45.94260 423710 5088141 1522
Mushroom ASHES -130.01380 45.93360 421405.3 5087167.9 1548
Nascent North SRZ -129.98152 45.93577 423911 5087378 1520
Old Flow North SRZ -129.98170 45.93645 423897.5 5087454.7 1534
Old Worms North SRZ -129.98331 45.94510 423785 5088418 1528
Ouzo North SRZ -129.98468 45.94582 423679.6 5088496.8 1526
Oxide North SRZ -129.98508 45.94545 423647.9 5088456.4 1543
Pillar North SRZ -129.98542 45.92270 423591 5085929.1  
Porkchop ASHES -130.01422 45.93332 421373 5087136 1547
Roof North SRZ -129.98448 45.94250 423689.8 5088129.1 1523
ROPOS ASHES -130.01405 45.93328 421386.1 5087134.1 1547
Snail North SRZ -129.98188 45.93317 423878.6 5087089.7 1525
Snow North SRZ -129.98245 45.92712 423827 5086417  
Snow Blower North SRZ -129.98407 45.93987 423719 5087835 1521
Steve Mound ASHES -130.01342 45.93325 4214348 5087128.6  
Styx ASHES -130.01370 45.93328 421412.2 5087132.2  
The Pit North SRZ -129.98408 45.93975 423718.2 5087823.2 1521
Tombstone ASHES -130.01133 45.92948 421590 5086597  
Tunnicliff ASHES -130.01582 45.93367 421248.7 5087178 1544
Virgins Daughter ASHES -130.01340 45.93375 421436 5087184  
Virgin ASHES -130.01348 45.93365 421430 5087174 1547
White ASHES -130.01363 45.93373 421419 5087182.9  
91Vent NRZ -130.01242 46.03860 421661.4 5098834.3  
Shepherd CASM -130.02668 45.98990 420486.4 5093373.6 1583
South Casm CASM -130.02625 45.98870 420518.6 5093304.6 1583