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1.7 KiB

Preprocessing

The preprocessing pipeline that is developed at the Berlin State Library comprises the following steps:

Layout Analysis & Textline Extraction

Layout Analysis & Textline Extraction @sbb_pixelwise_segmentation

OCR & Word Segmentation

OCR is based on OCR-D's ocrd_tesserocr which requires Tesseract >= 4.1.0. The Fraktur_5000000 model, which is trained on GT4HistOCR is used. corpiu The PAGE-XML produced by the Layout Analysis & Textline Extraction is taken as input, and the output is PAGE-XML containing the text recognition results with absolute pixel coordinates describing bounding boxes for words.

Tokenization

Named Entity Recognition

For Named Entity Recognition, a BERT-Base model was trained. sbb_ner is using a combination of unsupervised training on a large (~2.3m pages) OCR corpus in combination with supervised training on a small (50k tokens) annotated corpus. Further details are available in the paper.