Suunnanlaskuja

Suunnanlaskuja is a Finnish term referring to a family of calculations used to determine direction and orientation in geographic and geometric problems. In practice, suunnanlaskuja covers bearings, azimuths, course, and heading calculations for moving objects or reference frames. The concept is central in navigation, surveying, astronomy, and geoinformatics, and it also appears in robotics and autonomous systems.

Key ideas include bearings (angles relative to a reference direction, usually north), headings (apparent travel direction), and reference frames such as true north and magnetic north. When working with points on the Earth's surface, suunnanlaskuja distinguishes between great-circle navigation, which follows the shortest path on a sphere, and rhumb line navigation, which maintains a constant bearing. Coordinate representations (lat/lon) and their projections are common inputs and outputs.

Common computations include determining the initial bearing from point A to point B. A standard form, with lat and lon in radians, is bearing = atan2(sin(dlon) * cos(lat2), cos(lat1) * sin(lat2) - sin(lat1) * cos(lat2) * cos(dlon)), where dlon = lon2 - lon1. Distance between points is often computed with the haversine formula. Transformations between geodetic coordinates and projected coordinates, as well as converting bearings to compass directions, are also part of suunnanlaskuja.

Applications include navigation for ships and aircraft, land surveying, GIS analysis, and the control of autonomous vehicles. Local magnetic declination, datum differences, and Earth curvature are important considerations, and different regions may use different reference ellipsoids.