1 Lab 17-1 ONLINE LESSON. 2 If viewing this lesson in Powerpoint Use down or up arrows to navigate.

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Lab 17-1 ONLINE

LESSON

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Do take notes as we peruse through this

lesson…

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Azimuth and Distance

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An azimuth is a compass direction from one point to

another…

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To use azimuth…a reference point must

be established…

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The north pole of Planet Earth can be used as a reference point.

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Place a protractor on the surface of our planet.

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The “N” of the protractor matches the “N” of our planet…

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“N” stands for north!

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North is a reference on our planet.

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Now we can find an azimuth…

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From the middle of the protractor…where the blue star resides

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To the green star…is an azimuth…a compass direction.

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The azimuth is 35° true

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A back azimuth is just an azimuth in the

opposite direction…

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From the green star to the blue star…

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The back azimuth is 215° true

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Adding 180° to 35° produces a back azimuth of 215.

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RULE #346:

If an azimuth is 180° or less…then add 180

° for a back azimuth

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RULE#9999:

If an azimuth is 181 or more…then

subtract 180 for a back azimuth

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We can find azimuths using maps and

charts…

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A map or a chart is a small graphical

representation of the surface of the

planet…

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Maps represent

land…

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Charts represent the ocean…

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To find an azimuth on a map or chart… two

locations are needed…

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An origination point (A) and a destination

point (B)…

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A

B

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Mark 2 locations on the chart with a green dry erase marker…

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With a green dry erase marker draw a line between the 2

points……

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Place a protractor on the chart…

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Make sure that the protractor’s

north/south axis is aligned with the

north/south axis of the chart…

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The north/south axis of the protractor must

be parallel with the north/south axis of

the chart…

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Then read the azimuth…

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The azimuth is 120° true…

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Distances can be determined from

maps and charts…

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There is a distance scale on the San

Francisco Bay chart …it is located at the

top of the chart.

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scale

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The scale represents 2 nautical miles.

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scale

1 nautical mile (nm)

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scale

1 nautical mile (nm)

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scale

2 nautical miles (nm)

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With a ruler, measure the length of a 1

nautical mile segment of the distance

scale…

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The length should be about 9.2 cm

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Use this relationship…

1nm9.2 cm

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To determine the distance between two points on a

chart…

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Draw a line with a dry erase marker between 2

points…

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Then measure the line in centimeters…

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If the line is 29 cm… use the relationship…

1nm9.2 cm

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1nm9.2cm

x29cm

=

Solve for “X”…

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The distance on the chart is 3.2 (nautical

miles) nm

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Referring to page 5 of Lab 62, a metric distance can be

calculated…

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This same ratio is seen on the Metrics

at a Glance reference guide…

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Ask Bob for Lab 17-1Q questions

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END

L17-1