Running Fix With Bearings

Universitatea Maritima din Constanta Terrestrial Navigation

Assist.Prof. Costel STANCA

Fixing by TWO bearings of a single object with a

time interval between observations (running fix)


2

Use of method

- ONLY when just a single object is visible at a moment and no

other LOP is possible to be obtained, so NO simultaneously

observations may be performed.

- At the same object will be measured a second bearing after an

elapsed time.

- The time waited to the second observation must be enough in such a

way that a proper intersection of LOPs will be obtained.

- The first LOP will be transferred for the second moment.

- The obtained point is a RUNNING FIX.

- Between the two observation COURSE & SPEED must be

UNCHANGED.

- This method could be used for two objects observation when at the

time of first observation only one is visible.


3

Running fix with one AtoN

1. Identify the AtoN in the chart and estimate the two moments for

observations in such a way to assure a proper angle of intersection for

the two LOPs (300-1500).

2. Identify CORRECTLY on site the AtoN selected to be used.

3. Measure the bearing. Note the time.

4. Correct the bearing to obtain TRUE BEARING.

5. Line up the bearing on chart.

12.00


4


6. Wait until the bearing will be changed with more than 300 keeping course

and speed unchanged.

7. Measure the second bearing to the same object. Note the time.


9. Line up the second bearing on chart.

12.30

12.00


5


10. Transfer the first LOP to the second moment:

- Draw a parallel through the AtoN to the ships course

- Mark on this parallel the distance sailed by the ship between observations

- Draw through this point a parallel to the initial bearing line

11. The RUNNING FIX is at the crossing point of the two bearing lines.

12. Read the latitude and longitude.

13. Measure the fixing error (bearing and distance from DR to RUNNING FIX).

14. Draw the course line from the RUNNING FIX.

12.30

12.00


6

Running fix with two objects

1. Identify the two objects in the chart in such a way to assure a proper

angle of intersection for the two LOPs (300-1500).

2. Identify CORRECTLY on site the first visible object.

3. Measure the bearing. Note the time.


5. Line up the bearing on chart.

12.00


7


6. Wait until the second object will become visible keeping course and speed

unchanged.

NOTE: FIRST OBJECT WILL BE NOT VISIBLE ANYMORE. IF IS

STILL VISIBLE WILL BE MEASURED THE BEARINGS TO THE 2

OBJECTS OBTAING A FIX.

7. Measure the second bearing to the SECOND object. Note the time.


9. Line up the second bearing on chart.

13.0012.00


8


10. Transfer the first LOP to the second moment:

- Draw a parallel through the first AtoN to the ships course

- Mark on this parallel the distance sailed by the ship between observations

- Draw through this point a parallel to the initial bearing line

11. The RUNNING FIX is at the crossing point of the two bearing lines.

12. Read the latitude and longitude.

13. Measure the fixing error (bearing and distance from DR to RUNNING FIX).

14. Draw the course line from the RUNNING FIX.

13.0012.00


9

Running fix analysis

Advantage

- Obtain the position with only one visible object and one LOP type

Disadvantages

- Longer time spent to obtain position

- Potential errors at the LOP transfer

- Need to not change course and speed

- Errors related to keeping course and speed constant

NOTE:

ALWAYS BETTER TO HAVE A FIX THAN A RUNNING FIX.

Running Fix With Bearings

Documents

Transcript of Running Fix With Bearings