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METHOD IVMultiple TargetsMethod IV:In multiple targets (er) and (er1) has the same distance and parallel to each other in every vector triangle when plotted, has the same time of observation and TMx.Sample Problem:OC = 015OS = 14 kts.Target ObservationsABCTimeBDBDBD1211 H35012 mi07012 mi11110.7 mi1223 H3489.5 mi0709.5 mi1138.1 miMultiple TargetsWhen dangerous target range 6 miles, you alter course to 060T starboard at the same time change speed, so that the target pass ahead your vessel on 2 miles danger zone.

What is the dangerous target?NSrm:NDRM:NBCPA:NCPA:A= A=A=A=B= B=B=C=C=C=C=1. TMx =2. NOS =REQUIRED

OC=015OS=14ktsR1. Plot OC and take note OS.

OC=015OS=14ktsM1 1211HM2 1214HM1 1211HM2 1214HM1 1211HM2 1214HmrmrmRr2. Plot the bearing and distance of all the targets. Target ATarget BTarget C

OC=015OS=14ktsRMLRMLM1 1211HM2 1214HM1 1211HM2 1214HSRM=12.5ktsSRM=12.5ktsSRM=13ktsM1 1211HM2 1214HmrmrmRRMLr3. Plot the RML and find the Srm of all the targets. Target AT(diff) = TM2 TM1 = 1223H 1211H = 12 minSRM = [D(MRM)T] x 60 = (2.512) x 60 = 12.5 knotsTarget BT(diff) = TM2 TM1 = 1223H 1211H = 12 minSRM = [D(MRM)T] x 60 = (2.512) x 60 = 12.5 knotsTarget CT(diff) = TM2 TM1 = 1223H 1211H = 12 minSRM = [D(MRM)T] x 60 = (2.512) x 60 = 12.5 knots

OC=015OS=14ktsRMLRMLM1 1211HM2 1214HM1 1211HM2 1214HSRM=12.5ktsSRM=12.5ktsSRM=13ktsM1 1211HM2 1214HmrmrmRRMLr4. Bring OC line to r of all the targets and make a line from r opposite to your OC.

OC=015OS=14ktsRMLRMLM1 1211HM2 1214HM1 1211HM2 1214HSRM=12.5ktsSRM=12.5ktsSRM=13ktseM1 1211HM2 1214HmremremRRMLr2.8 miles5. Form the vector triangle. Finding eD(e-r) = (OS x t) 60 = (14 x 12) 60 = 2.8 miles

OC=015OS=14ktsRMLRMLM1 1211HM2 1214HM1 1211HM2 1214HSRM=12.5ktsSRM=12.5ktsSRM=13ktseM1 1211HM2 1214HmremremRRMLr6. Identify which among the target is the most dangerous, based on your COLREG (International collision regulation).. Target B is the most dangerous

OC=015OS=14ktsRMLRMLM1 1211HM2 1214HM1 1211HM2 1214HSRM=12.5ktsSRM=12.5ktsSRM=13ktseNRMLNDRM=270M1 1211HM2 1214HNBCPA=000TMx=1240HmremremRMxRMLrNCPA=1.2miMxTMx=1240HRMx=6mi3.5 miles7. Draw danger zone, locate the Mx and draw your NRML on the most dangerous target (Target B), the find the TMx. Finding NBCPANBCPA = NDRM + 90 = 270 + 90 = 000Finding TMxTMx = [D(MMx) S(Srm)] x 60 + TM2TMx = (3.5 12.5) x 60 + 1223H = 17min + 1223H = 1240 H

OC=015OS=14ktsRMLRMLM1 1211HM2 1214HM1 1211HM2 1214HSRM=12.5ktsSRM=12.5ktsSRM=13ktseNRMLNDRM=270M1 1211HM2 1214HNBCPA=000NOC=060TMx=1240HmremremRr1MxRMLrRMx=6mi8. Locate r1 of the most dangerous target (Target B).

OC=015OS=14ktsRMLRMLM1 1211HM2 1214HM1 1211HM2 1214HSRM=12.5ktsSRM=12.5ktsSRM=13ktseNRMLNDRM=270M1 1211HM2 1214HNBCPA=000NOC=060TMx=1240HmremremRr1NSRM=25ktsMxRMLrRMx=6mi4.9 miles9. Once r1 has already obtained, connect it to m and find for NSrm.Finding NSrmNSrm = [D(m-r1) t] x 60NSrm = (4.9 12) x 60 = 24.5 knots or 25 knots

OC=015OS=14ktsRMLRMLM1 1211HM2 1214HM1 1211HM2 1214HSRM=12.5ktsSRM=12.5ktsSRM=13ktseNRMLNDRM=270M1 1211HM2 1214HNBCPA=000NOC=060TMx=1240HmremremRr1NSRM=25ktsNOS=20ktsr1Mxr1RMLrRMx=6mi10. Connect your r1 to e and transfer it to all other target. (Same e-r1 because it is your NOC and NOS.Finding NOSNOS = [D(e-r1) t] x 60NSrm = (3.9 12) x 60 = 19.5 knots or 20 knots3.9 miles

OC=015OS=14ktsRMLRMLM1 1211HM2 1214HM1 1211HM2 1214HSRM=12.5ktsSRM=12.5ktsSRM=13ktseNRMLNDRM=270M1 1211HM2 1214HNBCPA=000NOC=060TMx=1240HmremremRr1NSRM=25ktsNOS=20ktsr1NSRM=15.5ktsMxNSRM=27ktsr1RMLrRMx=6mi5.4 miles3.1 miles11. Connect r1 to m on all other target and find for NSrm. Finding NSrm (A)NSrm = [D(m-r1) t] x 60NSrm = (3.1 12) x 60 = 15.5 knotsFinding NSrm (C)NSrm = [D(m-r1) t] x 60NSrm = (5.4 12) x 60 = 27 knots

OC=015OS=14ktsRMLRMLM1 1211HM2 1214HM1 1211HM2 1214HSRM=12.5ktsSRM=12.5ktsSRM=13ktseNRMLNDRM=270M1 1211HM2 1214HNBCPA=000NOC=060TMx=1240HmremremRr1NSRM=25ktsNOS=20ktsr1NSRM=15.5ktsMxTMx=1240HMxNSRM=27ktsr1RMLrMxTMx=1240HRMx=6mi3.7 miles3.5 miles12. Locate Mx on all other target by finding distance m-Mx. Finding D(m-Mx) A(m-Mx)D = [S(Srm) x t(TMx-TM1] 60 = [12.5 x (1240H-1223H)] 60 = (12.5x17) 60 = 3.5 milesFinding D(m-Mx) C(m-Mx)D = [S(Srm) x t(TMx-TM1] 60 = [13 x (1240H-1223H)] 60 = (13x17) 60 = 3.7 miles

OC=015OS=14ktsRMLRMLM1 1211HM2 1214HM1 1211HM2 1214HSRM=12.5ktsSRM=12.5ktsSRM=13ktseNRMLNDRM=270M1 1211HM2 1214HNBCPA=000NOC=060TMx=1240HmremremRr1NSRM=25ktsNOS=20ktsr1NSRM=15.5ktsMxNDRM=235NSRM=27ktsr1RMLrMxTMx=1240HRMx=6miNRMLNCPA=6miMxNBCPA=325TMx=1240H13. Once the Mx has been obtained, bring your r1 m at Mx and draw your NRML and find for the NDrm, NBCPA and NCPA. Finding NBCPA ANBCPA = NDRM + 90 = 235 + 90 = 325

OC=015OS=14ktsRMLRMLM1 1211HM2 1214HM1 1211HM2 1214HSRM=12.5ktsSRM=12.5ktsSRM=13ktseNRMLNDRM=270M1 1211HM2 1214HNBCPA=000NOC=060TMx=1240HmremremRr1NSRM=25ktsNOS=20ktsr1NSRM=15.5ktsMxTMx=1240HMxNRMLNDRM=235NBCPA=325NSRM=27ktsr1RMLNRMLNDRM=285NBCPA=195rNCPA=6miNCPA=1.2miMxTMx=1240HRMx=6mi13. Once the Mx has been obtained, bring your r1 m at Mx and draw your NRML and find for the NDrm, NBCPA and NCPA. Finding NBCPA CNBCPA = NDRM - 90 = 285 - 90 = 195

OC=015OS=14ktsRMLRMLM1 1211HM2 1214HM1 1211HM2 1214HSRM=12.5ktsSRM=12.5ktsSRM=13ktseNRMLNDRM=270M1 1211HM2 1214HNBCPA=000NOC=060TMx=1240HmremremRr1NSRM=25ktsNOS=20ktsr1NSRM=15.5ktsMxTMx=1240HMxNRMLNDRM=235NBCPA=325NSRM=27ktsr1RMLNRMLNDRM=285NBCPA=195rNRCPA=6miNRCPA=1.2miMxTMx=1240HRMx=6miANSWERS1. TMx = 1240H2. NOS = 20 knotsNSrm:NDRM:NBCPA:NCPA:A= 15.5 kts.A= 235A= 325A= 6 miB= 25 kts.B= 270B= 000C= 1.2 miC= 27 kts.C= 285C= 195END