Within what distance of the point of tangency is distortion on a Gnomonic chart tolerable?

On a Gnomonic chart, distortion increases rapidly as you move away from the point of tangency, which is the location where the chart projection is most accurate. The correct answer indicates that distortion is generally considered tolerable within a distance of 1000 nautical miles from this point. This is significant because Gnomonic charts are primarily used for plotting great circle routes—essential for long-distance navigation—due to their representation of the shortest distance between two points on the globe.

The choice of 1000 nautical miles reflects a balance between reasonable navigational accuracy and the practical limits of charting distortion. Beyond this range, the inherent characteristics of the Gnomonic projection make it less useful for precise navigation, as the shape and distances between features can become increasingly inaccurate. The correct answer reflects the standard practices in navigation and seamanship to ensure safety and efficiency during voyages. Understanding these limits is crucial for navigators, enabling them to make informed decisions regarding route planning and chart selection.