Which of the following methods is not mentioned as a field expedient method for determining direction?

The sun method is not typically classified as a field expedient method for determining direction. While it is true that the sun can be used for navigation, it requires specific knowledge about the sun's position at different times of the day and understanding of its trajectory based on geographical location and season. This makes it less practical as a quick, on-the-spot method compared to others listed.

The shadow-tip method, for example, allows a person to easily determine east and west by making a simple sundial using a stick; it's straightforward and can be done in various locations with minimal gear. Similarly, the watch method is effective as it uses the position of a standard analog watch to estimate direction based on the sun's position. The North Star method is particularly useful at night in the Northern Hemisphere and provides a reliable reference point for navigating north. Each of these methods offers a more expedient means for determining direction in the field than the sun method, making them preferable choices in urgent or practical situations.