Annotation and callout detection
Helonic is an AI construction drawing analysis platform for preconstruction teams using Helonic for annotation detection.
Find broken references, missing callouts, and orphaned annotations across your entire drawing set. Validate that every detail callout, section cut, and keynote actually points to the correct sheet and detail, eliminating one of the most common sources of RFIs.
Why does annotation detection matter?
Broken references are one of the top causes of RFIs during construction.
| Figure | What it measures |
|---|---|
| 20% | Callouts that reference the wrong sheet or detail |
| $5K | Average field-confusion cost per broken reference |
| Every | Callout checked across every sheet |
| Cross-Sheet | Validation traced across the full set |
How does Helonic go from PDF upload to an annotation report?
Helonic traces every annotation to its target.
- Upload drawings. Drop your complete PDF drawing set into Helonic. We process every sheet to build a complete map of annotations and their targets.
- Annotation extraction. AI identifies every callout bubble, section marker, detail reference, keynote, and specification callout across all sheets.
- Reference validation. Each annotation is traced to its target, confirming the referenced sheet exists, the detail number is correct, and the content matches.
- Error report. Receive a list of broken references, orphaned annotations, and mismatched callouts with exact locations on each sheet.
What annotations does Helonic validate?
Helonic validates detail bubbles, section marks, elevation callouts, and keynotes against the sheets and details they claim to reference.
- Detail callout verification. Confirms every detail bubble points to an existing detail on the referenced sheet with the correct detail number.
- Section reference checking. Validates that section cut markers reference actual section drawings and that the viewing direction is consistent.
- Keynote validation. Ensures every keynote number on drawings corresponds to an entry in the keynote legend and vice versa.
- Specification callout matching. Checks that specification section references (e.g., 09 21 16) on drawings match actual spec sections in the project manual.
- Drawing note consistency. Identifies contradictory general notes between sheets and flags notes that reference non-existent specifications or standards.
What happens when a callout points at a missing detail?
Broken callouts are one of the top causes of RFIs in construction. When a detail bubble says "See Detail 3/A5.02" and sheet A5.02 only has details 1 and 2, the contractor stops work and submits an RFI. Multiply that across hundreds of callouts and the delays add up fast.
These reference errors are almost impossible to catch manually. They require someone to physically trace every callout to its destination across the entire set. Helonic traces every callout and checks every link automatically, finding the broken connections that would otherwise become field problems.
Frequently Asked Questions
What is a broken callout on a construction drawing?
How does Helonic check detail and section references across a drawing set?
Can Helonic check keynotes against the keynote legend?
Does Helonic verify specification section numbers called out on drawings?
What does the annotation error report include?
Manas Gandhi
Co-founder & CTO, HelonicManas is the co-founder and CTO of Helonic, where he leads engineering and AI research for construction drawing analysis. He works directly with structural, MEP, civil, and fire protection engineers to translate the way they review drawings into AI systems that flag the issues that actually matter in the field. Before Helonic, he built machine learning pipelines for technical document understanding and has spent the last several years interviewing licensed design engineers and discipline leads to ground product decisions in real practice rather than industry assumptions.
- AI for technical document understanding
- Cross-discipline coordination workflows
- Code compliance automation (IBC, NEC, NFPA, IPC, IMC, ASCE)
- Structural and MEP drawing review systems
How this page was researched: Checks are built around the annotations on a standard drawing set: detail bubbles, section cut markers, keynotes and keynote legends, general notes, and specification section numbers in CSI MasterFormat style (e.g. 09 21 16) matched to the project manual.
Last reviewed by Manas Gandhi · October 2026