Wednesday, June 17, 2009

SOA and OGC Standards for AIM - Part 2, New Data Standards

This is the second part of our blog series focused on OGC standards for Aeronautical Information Management (AIM) - in this edition we look at new data standards for AIM. The first part is available here.

In October 2009 the Open Geospatial Consortium (OGC) kicked off its sixth Web Services Interoperability Initiative (OWS-6). This six month global effort investigated prototypes, and implemented and tested interoperability standards. Among the five threads of the testbed was the Aeronautical Information Management (AIM) thread. Sponsored mainly by the U.S. Federal Aviation Agency (FAA) and EUROCONTROL, various federal agencies and commercial companies collaborated in the testing of emerging standards and implemented cutting edge technologies following an aviation scenario.

The next generation of digital information flowing in and out of the cockpit will be rich in details including temporal information as well as geospatial elements. The chosen base specifications are Geography Markup Language (GML) and a derivative called Aeronautical Information Exchange Model (AIXM). These XML driven specifications provide the current and future standards for aeronautical information system requirements.

The OWS-6-AIM testbed demonstrated the AIXM spatiotemporal qualities and the temporal deltas-based updates received from a web service. The data included Navaids, airports data such as runways, taxiways and much more. Another AIXM driven specification is the xNOTAM, a new standard that adds significant depth to the current NOTAM abbreviation. A key assumption of the AIXM Temporality model is that any feature property may change in time, except for the feature identifier. The changes are conveyed via time-slices containing only changed information via ‘deltas’. This methodology is designed to reduce bandwidth especially when dealing with potentially large amounts of data with minor changes taking place over time. For example, a baseline data layer of airports runways can be loaded while the plane is still on the ground, accounting for all geometries and included information this may be a relatively large file. During flight, when bandwidth is lower and connection is not as dependable, updates such as notification of a runway status change will only require a minor amendment to the baseline data. This change is provided as a relatively small update. Furthermore some of the changes will have a specified duration and will allow the system to account for that preset interval without any need for further updates.

To handle the AIXM spatiotemporal data The Carbon Project enhanced its CarbonTools PRO GML parser and data modules to support the AIXM model. The AIXM parser reads the time-slices of the features and stores the interpreted data in a feature component. The data modules expose a method to set the time represented by the class and internally resolve the collection of temporal updates into a correct snapshot view of the feature. In other words, the data modules preserve the history of the contained features and generate from the partial updates an accurate feature snapshot according to a set date and time. With this capability at hand the application can set the temporal state for every AIXM based data layer, effectively creating a time accurate display. For the testbed purposes we used a user operated time-slider and added the ability to animate the complete demo scenario.

Weather data also played a key role in the testbed. The Carbon Project demonstrated two sources; one was real-time TAFs and METARs provided by NOAA using GML and the Weather Information Exchange Model (WXXM). The other was cloud radar imagery provided using a Web Map Service (WMS) by CustomWeather, a commercial partner of The Carbon Project. The seamless integration of the various existing sources of real-time weather information show how various elements in the interoperable NextGen aviation systems can already be used in today’s solutions.

- Jeff H and Nuke G


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