atan2sindlon

atan2sindlon is a computational function commonly found in programming languages and mathematical libraries. It is designed to calculate the angle of a 2D vector given its Cartesian coordinates, represented by a delta longitude (dlon) and a delta sine latitude (sindlon). The function is an extension of the standard arctangent function, atan2, which typically takes y and x coordinates as input. In the context of geospatial calculations, dlon represents the difference in longitude, and sindlon represents the sine of the difference in latitude.

The primary purpose of atan2sindlon is to determine the direction or bearing between two points on the Earth's surface. Unlike simpler trigonometric functions that might return an ambiguous angle or fail in certain quadrants, atan2sindlon correctly handles all possible input values, providing an angle in the range of -π to +π radians (or -180 to +180 degrees). This makes it robust for calculating bearings in navigation, mapping, and other geodetic applications where precise directional information is crucial. The use of the sine of the latitude difference is often employed in formulas related to spherical trigonometry and great-circle distances.