UTM2LL-bgol (Convert UTM Point to Lat/Long, In-Drawing)

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 UTM-to-Latitude/Longitude coordinate conversion tools used in survey/GIS workflows (traditionally offered as a web-based SaaS application requiring an account and a CSV upload). This is an original, independently written, entirely AutoLISP-native routine, new file name, new command name, new source code, created so the CAD community has a free, in-drawing alternative that needs no browser, account, or file upload.

Overview

U2LL converts a UTM coordinate, picked directly from the drawing, where the point's X is treated as Easting and Y as Northing, into approximate geographic Latitude/Longitude, using the standard WGS84 ellipsoid and inverse Transverse Mercator projection formulas. The result is written back into the drawing as a text label next to the converted point, so survey points laid out in CAD can be cross-referenced against Google Maps/Earth-style coordinates without ever leaving the CAD session.

How to Use

1. Load UTM2LL-bgol.lsp into your CAD session (drag-and-drop the file onto the drawing window, or use the APPLOAD command).
2. Type U2LL at the command line and press Enter.
3. Enter the UTM zone number when prompted (defaults to 43).
4. Choose the hemisphere: North or South.
5. Enter the label text height (defaults to 2.0).
6. Pick the point in the drawing you want to convert, its drawing X coordinate is treated as UTM Easting, its Y coordinate as UTM Northing.
7. A new text label showing Latitude, Longitude in decimal degrees is created next to the point, on layer BGOL-U2LL (colour red).

Why Use It

• No web account needed, the original workflow this is inspired by requires signing into a web SaaS tool and uploading a CSV; U2LL does the conversion right inside your CAD session.
• Instant cross-reference, quickly check where a CAD survey point actually sits on Google Maps/Earth by reading its computed Lat/Long directly off the drawing.
• No installation, a single AutoLISP file, no separate application or browser tab required.

Where to Use It

• Cross-referencing UTM-based CAD/survey points against latitude/longitude -based systems like Google Earth or Google Maps.
• Quick sanity-checks on survey coordinate data (e.g. confirming a point falls in the expected zone/region) without a separate conversion tool.
• Any workflow needing an approximate geographic Lat/Long for a point already located in a UTM-based CAD drawing.

Notes

• Uses the WGS84 ellipsoid (a = 6378137.0 m, flattening 1/298.257223563) and a truncated-series inverse Transverse Mercator formula, accurate to within a few metres, well within tolerance for labeling and cross-reference purposes (not intended for legal/cadastral-grade geodetic work).
• The drawing's X/Y coordinates are assumed to already be in UTM Easting/Northing for the zone and hemisphere you specify; if your drawing uses a local or grid coordinate system, convert to UTM first.
• Only converts one point per run; run the command again for additional points, or wrap it in a loop for batch conversion.
• 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.