Track 02 · RetrievalLesson 08 of 11
Scans, forms and OCR at scale
Most enterprise input is scanned paper; extract it accurately and affordably.
- Lesson library · reference
- 35 min read
- 75 min hands-on
- Halden Freight
- Pro
What you'll be able to do
01- Explain the difference between OCR and document intelligence, and which one a given use case needs.
- Choose an engine per document class (printed, handwritten, form, table, non-Latin script) using verified language support, cost per page and data-handling terms.
- Implement CER and WER, field-level accuracy, and a confidence-plus-validation router that sends uncertain fields to human review.
- Design a pipeline that absorbs bursty volume with async jobs, batching and idempotent retries, and estimate its cost per page including review labour.
- Defend review rates and accuracy targets to a business sponsor using document-level, not field-level, arithmetic.
Before you start
- Parsing and chunking documents that fight back: what happens to text once you have it (chunking, layout-aware splitting). This file covers getting reliable text and fields out of images in the first place.
- Typed output: schemas, validation and tool calls: schema-driven extraction relies on the same JSON Schema and validation mechanics.
- Comfort with basic image concepts: resolution (DPI), greyscale, rotation.
The short version
OCR turns pixels into characters. Document intelligence turns a page into structure: reading order, headings, tables, key-value pairs, checkboxes, signatures and typed fields, each with a location and a confidence score. Enterprise documents (Halden Freight's bills of lading and customs declarations) are scanned, photographed, multilingual and partly handwritten, so you need both, plus the discipline around them: pre-processing, an engine choice per document class, deterministic validators, confidence thresholds calibrated on a labelled set, a human review queue for what fails, and throughput and cost controls for volume that arrives in bursts. The output metric that matters is not "OCR accuracy". It is the error rate of fields that were accepted without a human looking.
Key takeaways:
- Measure at three levels: CER/WER for text, field-level accuracy for extraction, and error rate among auto-accepted fields for the business.
- Confidence alone is not enough. Confident-and-wrong values exist; deterministic validators (check digits, formats, cross-field sums) catch many of them.
- Language and script support differ sharply between services. Verify per language before you promise anything.
- Vision-language models read messy documents well but can produce plausible values that are not on the page. Treat their output as untrusted until validated and grounded.
- At 95% per-field accuracy, a 20-field document is fully correct only about 36% of the time. Plan review capacity from that number.
Pro lesson
The rest of this lesson is in Pro.
The mental model, worked example, field note, failure table, exercise and self-check, with the voice tutor.
- Every stage and specialisation, in full
- Every lab and every role project
- Halden weeks 2–10, on your record
- Every drill, live in the playground
- All solutions, plus the server judge
- Lab Assistant and every Teach with AI