Chainage & Stationing Calculator
Read and write chainages in any style (1+050, CH-1+050, 12+345.678), add and subtract them, and work against a real alignment: the chainage and offset of any point, and the coordinates to set out at any chainage. Station text follows the same rules as BTPL's CAD chainage tool.
Read a chainage
A prefix such as CH, KM, STA or RD is understood, and the hyphen in CH-1+050 is treated as part of the prefix, not as a minus sign.
Chainage arithmetic
Convert a list of chainages
The alignment
Chainage equations (optional)
Use these when a revised alignment makes the station value jump — at 1200 m along, the chainage becomes 2+000 and carries on from there.
A point that falls off the end of the alignment is reported as such rather than being given a chainage it does not have.
Offsets are signed: a positive value is to the RIGHT of increasing chainage, a negative value to the left. Separate several with commas to get a full cross-section at every station.
Station text. The kilometre is split off first and the sub-kilometre remainder is rounded with integer arithmetic, never by formatting a float — which is why 999.9999 m prints as 1+000.000 and not 0+1000.000. Reading works the same way in reverse, and a prefix such as CH, KM, STA or RD is separated from the number before the sign is read, so CH-1+050 is chainage 1050 and not minus 1050. These are the same rules as BTPL's CAD chainage tool, so a station written on a drawing and one computed here agree. Along the alignment, the centre line is treated as a polyline through the vertices you give. The chainage of a point is the distance to the foot of the perpendicular from it, its offset is that perpendicular distance, and the side is L or R looking along increasing chainage. Curved alignments are handled by supplying the curve as vertices — a chord every few metres is enough for setting out, but a true arc definition is not read yet, so a long curve given as two tangents will be short by the versine.
Corridor surveys, setting out and as-builts
BTPL runs centre-line surveys, cross-sections and setting-out for highways, railways, canals and pipelines — with the control, the closures and the deliverables documented.