Whale
Watchers' Lingo: How Far Offshore?
Contributed
by Mike
Hawe, ACS/LA Volunteer
"BLOW,
300 degrees at 45 mil."
If you attend the ACS/LA
Gray Whale Census, you might hear this shouted by a volunteer. What
does it mean?
This is how observers call out a gray whale sighting. It means
a gray whale has just surfaced (someone saw its spout) at 300 degrees
on the compass and 45 millimeters from the horizon. Then the other
observers know right where to look. The binoculars we use have a built
in compass and reticles.
In the photo below, those line marks in the view are the reticles.
Each short
line measures 5 mils (millimeters). The longer lines are 10 mils apart.
Using this information, we can track the whale's migration path.
The chart below lets us estimate the distance
between us and the whale, or the whale's distance offshore.
 |
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.) |
| 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 below to find the answers.
- What relationship do you notice between the Mils and the distance offshore?
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