Improving CAD-GIS Interoperability from qocsuing's blog

Improving CAD-GIS Interoperability

CAD and GIS software systems have evolved largely independently but in parallel over the past 30 years. CAD systems have focused on automating the drafting process with electronic drawings. As such, these systems place high emphasis on 2D graphics, sketching, and coordinate geometry tools. The graphic is the database, and a drawing file is the persistence container, i.e., where the graphics are stored. Typical applications include project engineering and site design, facilities management, and construction drafting. CAD drawings are usually large in cartographic scale .To get more news about cad file download, you can visit shine news official website.

In contrast, GIS software systems have more formal data models with rule-based editing and topology as well as an emphasis on spatial analysis and high-end cartography. GIS data is stored and managed in databases. Typical GIS applications include mapping, site suitability analysis, and network analysis. The key points here are that at their core CAD and GIS are different and complementary; both are valuable technologies. Any attempt to build a single integrated CAD-GIS system is fraught with pitfalls. CAD systems pretending to be GIS suffer from poor handling of object attributes, limited and slow database links, and rudimentary spatial analysis and cartography capabilities. They offer limited capabilities for data integration and sharing. GIS trying to be CAD systems are often accused of being overly complex, being too slow at screen refresh, and having limited sketching and drafting capabilities.

Resolution of this dilemma lies in taking a best of breed approach and building better linkages between CAD and GIS software packages. This is exactly the kind of agenda that Esri has been following over the last 10 years.
There are three technologies used to integrate CAD and GIS software systems--file translation, direct read, and shared access to a database.

File translation involves conversion of data from one file format to another (e.g., DXF to SHP or SHP to DGN). Because of the differences in CAD and GIS data models and file formats, users need to specify the syntactic and semantic mapping. An example of file translation is the DWG-DXF-Coverage translator in ArcInfo Workstation.

Direct read is conceptually similar to file translation except that data is read and converted on the fly into memory. There is no intermediate format, just an in-memory representation in the GIS. For example, ArcView can read MicroStation DGN files directly so the CAD data can be visualized, queried, and printed in the same map as other GIS data.

An alternative to data conversion is shared access to a database. Technically, one system embeds an application programming interface (API) that allows access to data on the fly. Esri's CAD Client extension to ArcSDE allows MicroStation or AutoCAD users to store and retrieve CAD elements and GIS features in a DBMS. The ArcSDE access API is embedded inside the CAD system. The API shows up as tools in the CAD user interface.

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