Speed made good calculator

Speed made good, often abbreviated SMG, is the effective progress speed along a route measured from position fixes rather than from the path length of the track you actually followed. Skippers, pilots, fleet operators, and GPS log analysts ask a simple question after two position reports: how fast did we advance in a straight line between those points over the time that separated them? This speed made good calculator answers that question with a deterministic haversine great-circle distance between the two latitudes and longitudes, divided by the elapsed hours you supply. Results include distance in kilometres, nautical miles, and metres, plus SMG in kilometres per hour, knots, and metres per second—ready for marine, aviation, and land-nav contexts without unit converters on the side.

What speed made good means and how it differs from average speed

Speed made good is the ratio of straight-line displacement between two geographic fixes to the elapsed time between those fixes. On a sphere the straight line is the great-circle arc: the shortest surface path connecting fix one to fix two. Average speed uses the odometer or log distance you actually travelled, including detours, tacks, and traffic loops, so it can be much larger than SMG when the track wanders.

SMG answers how fast you made good toward the next waypoint in a straight-line sense; it is the number voyage planners compare against required speed of advance and against current or wind effects that pull you off the rhumb. When the two fixes coincide, distance is zero and SMG is zero for any positive elapsed time—stationary over ground in the straight-line sense. Use SMG when your source data is a pair of lat/lon timestamps; use path-length average speed when you already know total track distance including every bend.

What to enter and what you get back

Latitudes must lie in the closed interval from negative ninety to ninety degrees; longitudes must lie in the closed interval from negative one hundred eighty to one hundred eighty degrees. Elapsed hours must be strictly greater than zero because speed made good divides distance by time.

Example: a departure near Manhattan at about forty point seven one two eight north, seventy-four point zero zero six west, an arrival a few kilometres north-east half an hour later, yields a few kilometres of straight-line distance and an SMG on the order of urban transit speeds in km/h and knots. Fractional hours are allowed: fifteen minutes is zero point two five hours. Convert minutes to hours before calling if your log stores mm:ss rather than decimal hours.

Where speed made good is useful

Coastal and offshore sailing crews use SMG between successive GPS fixes to judge whether a current, a tack, or a routing choice actually improved progress toward the next mark, not merely increased water speed. Delivery fleets and long-haul trucking platforms compare SMG between depot geofences against scheduled speed-of-advance so late-risk alerts fire on true progress, not on noisy path-length averages swollen by urban loops. Aviation and UAV operators estimate ground progress between reported positions when ADS-B or telemetry samples arrive with timestamps but without a full integrated path.

Education and exam-prep sites that rank for speed made good calculator need a live tool whose free path matches the paid automation path on the same pure module. Pair this capability with a separate haversine distance tool when you only need the arc length, or with average-speed tools when your distance is already a path total rather than two fixes.