BLKALN-bgol (Create Marker Block Along Alignment)

Command Type: AutoLISP routine, works in AutoCAD, BricsCAD, ZWCAD, and most AutoLISP-compatible CAD platforms.
Developed by: BGol Community, bgol.in

Inspired by the general concept of attributed point-marker/block-creation utilities used to place numbered features (valves, manholes, fittings) along an alignment in survey and infrastructure drafting. This is an original, independently written routine, new file name, new command name, new source code, created so the CAD community has a free, editable, open-source alternative.

Overview

BALN places a numbered marker at a picked point on or near a selected alignment polyline. It automatically snaps the pick to the nearest point on the alignment and records that point's Easting, Northing, and Chainage (running distance from the alignment's start) as text alongside a circular marker symbol, exactly the kind of structured, per-point data infrastructure projects need for valve, manhole, or fitting schedules.

How to Use

1. Load BLKALN-bgol.lsp into your CAD session (drag-and-drop the file onto the drawing window, or use the APPLOAD command).
2. Type BALN at the command line and press Enter.
3. Select the alignment polyline (LWPOLYLINE or POLYLINE).
4. Pick a point on or near the alignment, the routine snaps to the closest point on the curve automatically.
5. Enter a marker/block number when prompted (press Enter to default to 1).
6. A circular marker plus three text labels (marker number, chainage, and Easting/Northing) are created on a dedicated layer, BGOL-BALN (colour blue), at the snapped point.

Why Use It

• One-step attribution: captures number, chainage, and coordinates in a single pick-and-type operation instead of measuring and typing each value separately.
• Snap-to-alignment accuracy: the marker is always placed exactly on the alignment curve, even if your pick point is slightly off it.
• Consistent output: numbered markers land on their own layer, ready for review, export, or further attribute-block workflows, matching the level of structure expected in a formal stakeout deliverable.

Where to Use It

• Placing numbered valve, manhole, hydrant, or fitting markers along a water supply, sewer, drainage, or utility alignment.
• Any infrastructure project needing structured point features (number + coordinates + chainage) captured directly from the drawing.
• Asset management and as-built documentation where each feature needs a consistent, labeled marker tied to its exact alignment location.

Notes

• Marker circle radius and text height are fixed at 1.2 and 0.9 drawing units respectively; adjust the circR / txtht values inside C:BALN in the .lsp file to suit your drawing scale.
• Chainage is measured along the selected alignment from its start point using the alignment's own curve parameterization, so it stays accurate even where the alignment contains arcs.
• Source code is fully open, feel free to study, modify, and redistribute it under the same open, free-for-all spirit.

Credits

Developed and shared for the CAD community by BGol Community. Website: bgol.in. Free and open-source, use it, modify it, share it, for personal or commercial work alike.