Claude Code digitises 17 legacy water-body maps
A GIS user reports digitising 17 legacy maps with Claude Code scripts after manual georeferencing, then correcting omitted colours and extraction errors in QGIS.
reddit.com
Suggested prompt
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Using [georeferenced maps] and [verified colour palette], develop extraction scripts for [features]. Compare every layer with its source, flag omitted colours and gridline confusion, and prepare vector outputs for my QGIS review.
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Sourced account- Source author
- u/Xcrispy02 on Reddit
- Original account
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- Reported result
- A GIS user reports digitising 17 legacy maps with Claude Code scripts after manual georeferencing, then correcting omitted colours and extraction errors in QGIS.
- Human involvement
- The author manually georeferences and performs QGIS quality review and corrections. They warn against using this exact method for legal precedent.
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How the agent did it
- Convert the legacy PDFs into high-resolution PNG maps.
- Georeference all source images manually in QGIS.
- Have Claude develop colour-based extraction and vectorisation scripts.
A GIS user describes converting seventeen maps from 2006 to 2012 into usable geospatial features. The source PDFs represented colour-coded streams and rivers, with more than 1,400 line features to digitise. Professionals still used the PDFs because vector datasets had never been released.
The author converted the maps to high-resolution PNGs and manually georeferenced them in QGIS. Claude Code developed scripts that identified relevant RGB values and connected nearby pixels of similar colours to form vector features. The author then reviewed and corrected the outputs in QGIS. Georeferencing was the longest manual stage; extraction also confused some gridlines and background layers with target features.
In comments, the author reports that an entire colour could be omitted and that additional tuning and manual comparisons were needed. Their approximate accuracy claim is not accompanied by an independent measurement method, so it should not become a guaranteed performance figure. The completed result was a digitised dataset after two afternoons of work and human cleanup. The author explicitly discourages treating this exact method as suitable for setting a legal precedent. The copyable detail is to anchor extraction to georeferenced source images and a known palette, then check completeness against the original map rather than accepting a visually plausible vector layer.
Prompt
Suggested prompt (written by Agents In Use, not the author's)
Source: Reddit · u/Xcrispy02 on Reddit
Frequently asked questions
Which stage stayed manual?
Georeferencing all 17 maps and reviewing and correcting vector outputs in QGIS were human tasks.
What extraction error occurred?
The author reports an entire colour being omitted, plus confusion between target features and similar gridlines or background layers.
Is the dataset an authoritative legal map?
The author explicitly discourages this exact approach for setting legal precedent; original source maps and review remain essential.
More details
Remaining steps
- Review omissions and background-layer confusion against the originals.
- Tune extraction and manually correct the resulting features in QGIS.
About this account
Claude Code creates image-processing scripts for colour extraction and vectorisation; human review identifies omissions and directs tuning.
Firsthand account by u/Xcrispy02 on Reddit; original publication date verified against Reddit created_utc 1775077532 = 2026-04-01T21:05:32Z. Outcomes are the author’s reports, not independently reproduced. Suggested prompt written by Agents In Use; not the author’s original prompt.
Credit: u/Xcrispy02 on Reddit
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Tools and topics
Claude Code · QGIS · PNG maps · RGB extraction
Legacy map digitisation · Georeferencing · Completeness review
Editorial completeness: 100/100. Measures documented fields, not agent performance or verified outcomes.