Offset Calculations
Compute perpendicular and oblique offsets, derive offset-point coordinates, and recover chainage and offset from observed coordinates.
Perpendicular Offset to a Survey Line
Give the line start coordinate, bearing, chainage and signed offset to obtain the foot and offset-point coordinates.
Baseline
Offset Observation
Oblique Offset
Resolve an oblique offset into its longitudinal and perpendicular components, then compute the resulting point coordinate.
Baseline
Oblique Measurement
Inverse Offset from Coordinates
Given two baseline points and an observed point, calculate the along-line chainage and perpendicular offset.
Baseline Points
Observed Point
Offset calculation reference
Perpendicular offset: first compute the baseline point at the specified chainage. A left offset uses the bearing rotated 90° counter-clockwise; a right offset uses a 90° clockwise rotation. Inverse offset: project the observed point onto the baseline direction to obtain chainage, and use the signed cross-product to obtain the perpendicular offset.