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Whale Watchers' Lingo: How Far Offshore?
Contributed by Mike Hawe, ACS/LA Gray Whale Census Volunteer

If you are a whale watcher, you watch the ocean for the spout of a whale that just surfaced to breathe. Then you announce the sighting by shouting something like this: "BLOW, 300 degrees at 45 mil." It means 300 degrees on the compass and 45 millimeters from the horizon. These words tell other observers know exactly where to look to see the whale. Everyone can then help track the whale's migration path.

Binoculars like those used by whale watchers have a built in compass and reticles. The line marks in the view (below) are the reticles. Each short line measures 5 mils (millimeters). The longer lines are 10 mils apart. How far away is the whale? The chart below guides whalewatchers to estimate the distance offshore. Practice with the questions at the bottom of this page!

1. Find the whale's spout.
2. Read the degrees on the compass.
3. Count the mils from the whale's spout to the horizon (at the top of the view).
4. How far offshore is the whale? (Use the chart below.)

How Far Offshore?

Mils (Millimeters)

Miles

Kilometers

2.00

4.71

7.50

3.00

3.58

5.70

4.00

2.90

4.60

5.00

2.42

3.80

6.00

2.00

3.20

7.50

1.72

2.70

8.70

1.51

2.40

10.00

1.34

2.20

12.50

1.09

1.70

13.70

1.00

1.60

15.00

0.92

1.10

17.50

0.60

1.20

20.00

0.71

1.10

22.50

0.63

1.00

25.00

0.57

0.90

27.50

0.52

0.80

30.00

0.48

0.70

35.00

0.41

0.65

37.00

0.39

0.60

40.00

0.36

0.57

45.00

0.32

0.51

50.00

0.29

0.46

55.00

0.27

0.43

60.00

0.24

0.38

65.00

0.23

0.36

70.00

0.21

0.33

75.00

0.20

0.32

87.50

0.17

0.27

100.00

0.15

0.24


Try This! How Far Offshore?

  • If you hear a fellow whale-watcher call "BLOW, 300 degrees at 45 mil," how far offshore is that whale?
  • Take turns with a partner to make up some whale sightings using the whale watcher's lingo. Use the official chart above to find the answers.
  • What relationship do you notice between the Mils and the distance offshore?

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