Microstation

MicroStation is a computer-aided drafting and design (CAD) software developed in the 1980s by Bentley Systems, Inc. This private company was founded in Exton, Pennsylvania, in 1983. The CAD acronym is used to designate a wide set of tools and software meant to assist engineers and architects in the design and creation of new geometric entities for their own projects. MicroStation is Bentley's principal CAD software package to design, generate, and edit 2D and 3D vector graphic objects and elements. The GIS and CAD worlds have traditionally maintained a strong connection, especially in the preliminary phases of a GIS project, which deal with data acquisition, capture, editing, and quality control.

MicroStation has its own native format to store the geographic information (geometry). This native vector format is the .DGN (DesiGN) format. The information stored in these design files is structured in levels, with each level reserved for a certain type of information based on its theme and geometry type (lines, complex strings, shapes, centroids, annotations, etc.). A user working in the data acquisition process will probably be responsible for the design of the internal structure of this DGN file, defining how the information will be organized, determining which kind of information will be placed in each level, defining and assigning different symbol characteristics to each level, and, optionally, renaming existing levels of information. All the entities stored at a single level inherit the assigned symbol characteristics and will be shown in the view windows, using the predefined symbology for each level. Other properties such as line style, weight, and color can be used to distinguish entities stored in the same level.

Given the close relationship in the early years of MicroStation's development between Bentley Systems and Intergraph, MicroStation was used as the graphics engine and file format for Intergraph's Modular GIS Environment (MGE). However, major changes recently introduced in MicroStation Version 8 (V8) to the design file structure led Intergraph to focus their development efforts on their Windows-based GeoMedia product line. For that reason, Intergraph decided not to port MGE to MicroStation V8.

Although MicroStation is a CAD software in the strict sense (used as an assistant for computer drawing), many GIS products can import DGN format files. There is also a MicroStation extension to bridge the gap between the CAD and GIS worlds: the GeoGraphics extension. Through this extension, additional geographic, spatial, and database capabilities and tools can be added to the standard MicroStation version. Some of the tools of the GeoGraphics extension are related to data cleaning processes and topology creation. These new tools and capabilities offer a better integration between MicroStation and GIS software packages by eliminating geometry errors from layers, validating [Page 286]connectivity between different entities contained in the DGN file, allowing the creation of polygons from lines, and providing a means to assign a coordinate system to a design file. Also, using the GeoGraphics extension, a project can be created in MicroStation that allows each entity in the design file to be linked to information in external databases in order to perform complex queries using SQL (Structured Query Language) syntax and to create thematic maps.

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