Using a protractor, the observer can scale direction from a map to an accuracy of how many mils?

The precision with which an observer can scale direction from a map using a protractor is typically around 10 mils. This level of accuracy allows for effective navigation and artillery targeting, as it provides a sufficiently precise measurement for military operations. The use of mils in this context is essential, as they are a unit of angular measurement that helps in converting between map and real-world applications, particularly in the field of artillery where precision is crucial for effective fire support.

Higher levels of accuracy, such as 20 mils or 100 mils, would be insufficient for the detailed adjustments often necessary in military operations. Consequently, utilizing a protractor to derive direction with a granularity of 10 mils strikes a balance between practicality and the precise requirements of the task at hand.