ZSHIFT-bgol (Bulk Z / Elevation Offset)

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 bulk elevation-offset utilities used in survey 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

ZADD adds a specified offset value to the Z (elevation) coordinate of every selected entity in one operation, a bulk Z-shift capability that native AutoCAD doesn't provide for arbitrary selections. It's the fast way to correct a systematic elevation/datum error or move an entire point set from a local/assumed datum to a real one.

How to Use

1. Load ZSHIFT-bgol.lsp into your CAD session (drag-and-drop the file onto the drawing window, or use the APPLOAD command).
2. Type ZADD at the command line and press Enter.
3. Select the entities to shift (points, blocks, text, etc., anything with a DXF group 10 base/insertion point).
4. Enter the value to add to Z (a negative value lowers the elevation).
5. Every selected entity's base point Z coordinate is updated in place, and a small confirmation marker is drawn at each new position on layer BGOL-ZADD.

Why Use It

• Fills a native gap, AutoCAD has no simple built-in bulk "add a value to every selected entity's Z" tool.
• Preserves relative elevations, every point shifts by the same amount, so the overall shape/profile of the point cloud is unchanged, only its overall vertical reference.
• Much faster than manual editing, avoids editing each entity's Z coordinate individually via Properties or grips.

Where to Use It

• Correcting a systematic elevation/datum error across an entire drawing's point/block dataset (e.g. after a benchmark correction is discovered).
• Converting a point set from a local/assumed elevation datum to a real datum by applying a single global offset.
• Any bulk elevation-adjustment task on survey point or block entities where many objects need the same Z correction applied at once.

Notes

• Works on any entity type that stores its base/insertion point under DXF group 10 (POINT, INSERT/block reference, TEXT, etc.); entities without a group 10 point are silently skipped.
• Only the Z ordinate is changed; X and Y are left exactly as they were.
• A small confirmation marker circle is drawn at each shifted point's new location on BGOL-ZADD for a quick visual check.
• 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: https://bgol.in/ Free and open-source, use it, modify it, share it, for personal or commercial work alike.