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Radar Plotting – Head Reach
Farhan Saeed
Example 1
Own vessel steering 000°T, speed 15 kts. Target A = 1000hrs - 040°T x 12.0nm,
1006hrs – 040°T x 10.5nm, 1012 – 040°T x 9.0nm.
Report on Target A for 1012hrs. At 1015 hrs engines are ordered Stop. At
1033hrs vessel is stopped in the water heading 350°T, Head Reach 1.8’. Find new CPA and cross ahead range of target A.
000 010 020030
040
050060
070080
090100
110120
130
140150
160170180190200
210220
230
240
250
260
270
280
290
300
310
320330
340350
0 1 2 3 4 5 6 7 8 9 10 11 12
000°T
000 010 020030
040
050060
070080
090100
110120
130
140150
160170180190200
210220
230
240
250
260
270
280
290
300
310
320330
340350
0 1 2 3 4 5 6 7 8 9 10 11 12
1000O
A 1012
000°T
W
1006
A'O'
1015
1033
6.0'
7.0'
Example 5
Own vessel steering 230°T, speed 12 kts. Target A = 0500hrs - 180°T x 9.0nm,
0506hrs – 180°T x 7.5nm, 0512 – 180°T x 5.9nm.
At 0515 engines are ordered SLOW. At 0524 vessel is steady at new speed of 6 kts after advancing 1.2 miles.
State estimated new CPA for the target A.
000 010 020030
040
050060
070080
090100
110120
130
140150
160170180190200
210220
230
240
250
260
270
280
290
300
310
320330
340350
0 1 2 3 4 5 6 7 8 9 10 11 12
000 010 020030
040
050060
070080
090100
110120
130
140150
160170180190200
210220
230
240
250
260
270
280
290
300
310
320330
340350
0 1 2 3 4 5 6 7 8 9 10 11 12
W
O
A
0500
0506
0512 A'
O'
0515
0524
1
2
3
2
3
05371.6'
Example 3
Own vessel steering 050°T, speed 8 kts. Target A = 1000hrs - 350°T x 12.0nm,
1006hrs – 351°T x 10.5nm, 1012 – 352°T x 9.0nm, 1018 – 354°T x 7.4nm
If from stopping engines, the head reach is 1.2’ after 18 mins, find the time at which to order stop so that the other vessel passes three miles ahead.
000 010 020030
040
050060
070080
090100
110120
130
140150
160170180190200
210220
230
240
250
260
270
280
290
300
310
320330
340350
0 1 2 3 4 5 6 7 8 9 10 11 12
O
W
050°T
A
000 010 020030
040
050060
070080
090100
110120
130
140150
160170180190200
210220
230
240
250
260
270
280
290
300
310
320330
340350
0 1 2 3 4 5 6 7 8 9 10 11 12
1000O
W
050°T
1006
1012
1018A
STOP
O'
1025
1043
WA
3.0'
4.2'
1.2'
