Work out chain survey offset instantly with clear inputs, formula shown and shareable results.
An oblique offset has to be resolved into a component perpendicular to the chain line and a component along it, which shifts the effective chainage. Once resolved, the point is plotted by moving along the line bearing and then at right angles to it, giving coordinates relative to the start of the line.
Offset resolution
Perpendicular = offset x sin(angle to line); along-line = offset x cos(angle to line)
Coordinates
Move effective chainage along the line bearing, then the perpendicular component at bearing plus 90 degrees
Perpendicular = offset x sin(angle to line); along-line = offset x cos(angle to line). An oblique offset has to be resolved into a component perpendicular to the chain line and a component along it, which shifts the effective chainage.
To locate a point that cannot be reached at right angles, or to fix a boundary corner by two oblique ties which also provides a check that a single perpendicular offset does not.
This calculator takes 4 inputs: Chainage along the survey line, Offset length, Angle of the offset to the chain line, Bearing of the chain line. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.