Interpretation of scanned engineering drawings - a high level approach

Razzaq, S.M., 1997. Interpretation of scanned engineering drawings - a high level approach. PhD, Nottingham Trent University.

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An engineering drawing is a description of a mechanical object which incorporates geometric and technical details as well as information concerning the manufacturing process. In the mechanical engineering domain, where the exact shape of an object is generally an essential aspect of the total product specification, a large part of the drawing represents the 3-D geometry. The drawing usually consists of three orthographic views, together with dimensions and other textual information.

Initial processing begins with scanning of the engineering drawing to produce a binary image that can be stored in a computer. Errors and distortions caused by the scanning process mean that it is not always possible to construct a complete 3-D model using only the low level geometric information. Additionally, simplifications made to the drawing further complicate the process, because some information may only be provided by textual annotations on the drawing. Therefore, it is necessary to interpret textual information to recover simplified features and correct errors and distortions before the reconstruction process takes place.

Reconstruction algorithms, building on previous work of [Shaw95] and others, have been implemented for recognising low level features on a scanned engineering drawing. The algorithm initially identifies and separates the orthographic views. The geometric entities within each view are then recognised, collinear lines are grouped and identified as visible, hidden or centre lines. The identified lines are associated with type identifiers.

High level algorithms have been developed to understand the technical details on the drawing. Annotations are analysed and associated with corresponding geometric representations. Simplifications on the drawings are made explicit for the bottom-up procedure whilst distorted features are recognised and corrected using the information provided by the text. This approach of understanding technical details attempts to model an aspect of human drawing interpretation, whereby an 'envelope of expectation' is developed.

Item Type: Thesis
Creators: Razzaq, S.M.
Date: 1997
ISBN: 9781369325065
Divisions: Schools > School of Science and Technology
Record created by: Laura Ward
Date Added: 25 Jun 2021 09:22
Last Modified: 01 Nov 2023 14:58

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