How is the magnetic azimuth determined from a map?

Determining the magnetic azimuth from a map involves aligning your compass with the features on the map, such as a known landmark or a grid line, and then measurable to true north. This process is crucial because it allows the user to establish a clear direction of travel based on the magnetic fields provided by the compass.

When aligning the compass, you rotate the housing until the magnetic needle is parallel to the orienting arrow inside the compass. The angle you measure from true north to your intended direction gives you the magnetic azimuth. This direction is essential for navigation as it indicates the bearing you need to follow towards your destination, taking into account the variation between magnetic and true north.

In this context, using the compass effectively and recognizing the magnetic characteristics involved is vital for accurate navigation and map reading. The other options do not contribute to determining the magnetic azimuth directly; distances and declination factors relate to map scale and navigation adjustment rather than the direct measurement of direction using a compass. Reading the currents of a nearby river does not provide any information on azimuth either but rather environmental context.