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Chainage and Offset to Coordinate Calculator

Calculate a point coordinate from a straight baseline, an absolute chainage and a signed perpendicular offset.

Chainage and Offset to Coordinate Calculator

Enter your data

Use consistent units and verify the point or flow direction.

No sign-in
m
m
m
Positive = left; negative = right, looking from baseline start to end.
Inputs are processed in this browser. This calculator does not send project data to a server.
Check before use: This is an independent calculation aid, not approved design information. Confirm inputs, units, coordinate order, tolerances and project conventions before construction or setting out.

Offset convention

This calculator uses the common signed convention: a positive offset lies to the left when looking from the baseline start point towards the end point. A negative offset lies to the right. Enter zero to calculate a point directly on the line.

How the coordinate is calculated

The baseline vector is converted to a unit vector. The chainage difference is applied along that vector, then the offset is applied along the left-hand perpendicular vector.

P = Start + unit-line × (target chainage − start chainage) + left-normal × offset

Chainages outside the segment

The mathematical line can be extended before the start or beyond the end. The result clearly warns when the requested chainage is not inside the two-point segment.

Frequently asked questions

Is the target chainage measured from zero?

Not necessarily. Enter the chainage assigned to the baseline start. The calculator subtracts it from the target chainage to obtain the distance along the line.

What happens with a negative offset?

A negative offset places the point to the right looking from the baseline start towards its end.

Does this support curved alignments?

No. This initial calculator uses a straight two-point baseline. Curved alignment and transition geometry require additional alignment data.