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6.2.5.3 Update Intervals
The implementation of the “Update Intervals” can be understood as an add-on to the existing event dissemination. As this feature has been designed using Subscription
Policies, it does not affect any internal filtering mechanisms. Thus, an additional component was designed to apply the Update Interval policy of a given subscription see
Figure 8.
Figure 9 Update Interval Internals
6.2.5.4 Simple Altitide Queries
The Altitude Queries implementation leveraged the WFS for applying the developed approach. A WFS providing Simple Altitude Queries capabilities provided all needed
methods to enable outsourcing of the actual altitude computation at the Event Service. This feature was integrated at the time of DNOTAM reception: A previously defined
subscription with altitude information for OWS-9, aixm:RouteSegment was identified to provide all necessary parameter was evaluated with a GetFeature request at the WFS.
For instance, when receiving an update on an aixm:Airspace, the query defined the following parameters:
Property “gml:identifier” was equal to the one received in the DNOTAM. Spatial Operator evaluated true for the aixm:RouteSegment of the Subscription.
If and only if the query returned a non-empty result, the DNOTAM matched the given subscription and was disseminated to the subscriber.
6.2.6 Luciad Web Processing Service
6.2.6.1 Introduction
An OGC Web Processing Service WPS is a service that enables the user to perform a process such as a computation on a service. One use case is to offload heavy
computation to a server, so that lightweight clients can rely on it without having to
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Copyright © 2013 Open Geospatial Consortium.
implement or perform the computation themselves. Each process is described in a WPS profile, which lists the available input parameters and the structure of the response.
Within the OWS-9 Aviation thread, the WPS was used for a number of processing tasks. Luciad provided a WPS service component based on its COTS software product
LuciadLightspeed to support the following OWS-9 use cases:
ePIB map generation
o Use case description: enable rendering of a list of Digital NOTAMs submitted by a user on top of an airport map. The response should be a
bitmap image, ready for embedding in an ePIB. o Solution: the logic to retrieve the airport map data and styling information
was implemented by a WPS profile. The result was an SLD that embedded the combined feature data Digital NOTAMs and airport layout features
and SE styling information, which was sent to an FPS for final rendering.
Geometry processing
o Use case description: support calculating the topology relation and intersection between two AIXM features, such as between a route and an
airspace as illustrated in Figure 10. o Solution: two WPS profiles are defined and implemented, one to check the
topological relationship between two AIXM features e.g. do the features intersect, is one feature contained in the other, are they touching, etc. and
one to calculate the actual intersection points between two AIXM features.
Figure 10 Example of an Intersection Between an AIXM Route and Airspace
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Geometry retrieval
o Use case description: support the retrieval of the geometry for non-spatial AIXM features. For instance, an AIXM Runway feature represents a
runway entity but does not contain the actual geometry; this is stored in RunwayElement features. The use case is to be able to determine and
retrieve the geometry, given the Runway feature.
o Solution: a WPS profile has been defined and implemented that accepts an
AIXM feature and that determines and retrieves its geometry from a WFS.
6.2.6.2 Functional overview
Kategori