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   |   December 3, 2007   |   By Safe Software

Creating Feature Geometry from AIXM Data

The Aeronautical Information Exchange Model (AIXM) is one of the more complex data exchange models currently in use. But according to PIXEL SOFTEK of Bangalore, even AIXM can be easily manipulated with FME. In a recent demonstration for a prospective customer, PIXEL SOFTEK used a simple combination of FME transformers to show how FME can be used to manage some of the intricacies of AIXM datasets.

aixm

AIXM is based on the Aeronautical Information Conceptual Model (AICM) – a detailed model that describes all the entities, attributes, relationships and rules associated with providing information about aeronautical entities such as airport runway patterns, airspace and flight procedure legs. One of the issues users face when working with AIXM is joining together several AIXM features to form complete AICM entities. Generating feature geometries can also be a challenge; since AIXM is XML-based, feature geometries are not specified in the dataset.

PIXEL SOFTEK’s demonstration showed how a data transformation workflow created with FME can easily address these challenges. Their example workspace generates both two- and three-dimensional geometries from an AIXM dataset: a polygon representing an airport runway and three-dimensional geometries representing obstacles at the end of the runway. The final results are written to a KML file for display in Google Earth™.

Creating the runway polygon requires five transformers. First, FME’s SubstringExtractor transformer retrieves lat/long coordinate values specifying the runway start and end points, as well as runway width, from AXIM XML user attributes on other runway-related features. After converting these values to decimal degrees using the DecimalDegreesCalculator, the runway start and end points are plotted with a 3DPointReplacer. Next, a PointConnector connects these points to plot the runway centerline. Finally, a Bufferer creates a polygon of the correct width to depict the runway.

To generate the three-dimensional features representing potential obstacles in the runway approach path, PIXEL SOFTEK’s workspace first creates vertical lines from the obstacle features in the AIXM file. A KMLDiagrammer then extrudes the obstacles to specific heights using elevation attributes associated with each obstacle. (The KMLDiagrammer is a unique, user-defined “custom transformer” created by packaging together a group of standard FME transformers. It is one of several custom transformers created by Dmitri Bagh of Safe Software and available at www.fmepedia.com.)