Traverse Tables Courses

Although you can enter the courses in 360° notation into your calculator sometimes it will automatically acquire a minus sign. This is because the right-angled triangle you are solving could be in any one of the four quadrants making up a compass. The answer

QUADRANTAL

DEGREES

QUADRANTAL

DEGREES

NOTATION

NOTATION

NORTH

360

NORTH

000

N5 °

W

355

N5 °

E

005

N 10 °

W

350

N 10 °

E

010

N 15 °

W

345

N 15 °

E

015

N20 °

W

340

N20 °

E

020

N25 °

W

335

N25 °

E

025

N30 °

W

330

N30 °

E

030

N35 °

W

325

N35 °

E

035

N40 °

W

320

N40 °

E

040

N45 °

W

315

N45 °

E

045

N50 °

W

310

N50 °

E

050

N55 °

W

305

N55 °

E

055

N 60 °

W

300

N60 °

E

060

N65 °

W

295

N65 °

E

065

N 70 °

W

290

N70 °

E

070

N75 °

W

285

N75 °

E

075

N 80 °

W

280

N80 °

E

080

N86 °

W

275

N86 °

E

085

WEST

270

EAST

090

S85 °

W

265

S85 °

E

095

S80 °

W

260

S80 °

E

100

S75 °

W

255

S75 °

E

105

S70 °

W

250

S70 °

E

110

18.4 Quadrantal Notation (continued overleaf)

18.4 Quadrantal Notation (continued overleaf)

QUADRANTAL DEGREES QUADRANTAL DEGREES

S60 °

W

240

S60 °

E

120

S55 °

W

235

S55 °

E

125

S50 °

W

230

S50 °

E

130

S45 °

W

225

S45 °

E

135

S40 °

W

220

S40 °

E

140

S35 °

W

215

S35 °

E

145

S30 °

W

210

S30 °

E

150

S25 °

W

205

S25 °

E

155

S20 °

W

200

S20 °

E

160

S 15 °

W

195

S 15 °

E

165

S 10 °

W

190

S 10 °

E

170

S5 °

W

185

S5 °

E

175

SOUTH

180

SOUTH

030° could be

= 30° east from north = = 30° east from south = = 30° west from north = 30° west from south

A course of

030° could be

= 30° east from north = = 30° east from south = = 30° west from north = 30° west from south

18.4 (Continued)

is the same for each quadrant. Traditionally, courses used to solve the traverse are described as between 0-90° east or west from north or south. You must work out which quadrant your answer is in and turn it into 360° notation. There is no snappy formula to provide the answer. You must work it out (see the tables in Figure 18.4).

Chartmaking

Home-Made Charts Charts for Coastal Passages

Representing our three-dimensional world on two-dimensional paper warps reality.

The distortion used on a particular map is called its projection. In 1569 Gerard Kramer, known professionally as Gerardus Mercator, invented the projection that bears his name.

Mercator's projection was an instant hit with navigators because it allowed them to draw their courses as straight lines. The secret behind this is that a Mercator chart thinks the world is a cylinder, and lines of longitude, instead of meeting at the poles, are parallel to each other. They do this by growing further and further apart as you travel north or south from the equator (see Mercator charts in Figure 19.1). This is only possible because the latitude scale varies while the longitude scale is constant. Every single second of latitude is slightly larger than its predecessor, whereas in real life, or on a globe, they are equal. Mercator never explained how he drew his charts. It was 30 years after his first chart that an Oxford don called Edward Wright worked out the maths behind the Mercator projection.

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