Access to Sensor Descriptions Data Processing using SensorML

Copyright © 2008 Open Geospatial Consortium, Inc. All Rights Reserved. 47

8.5 Access to Sensor Descriptions

The SOS service also provides access to a SensorML description which defines the pro- cedure by which observation were obtained. This procedure can be a sensor system or a simulator for instance. In order to accomplish this, the consumer of the following exam- ple first finds a sensor of interest advertised in the capabilities document provided by the service. It then issues a ‘DescribeSensor’ request using the ID specified in the capabilities document. If the ID is valid, the SOS service shall then return the corresponding Sen- sorML document after fetching it from a local database or any other proprietary system. SensorML DB SOS Consumer SOS Capabilities Document SOS DescribeSensor using SensorML documents DB Find Document Selected SensorML Doc GetCapabilities DescribeSensorid SensorML System Proprietary Operation The SensorML document contains information about the sensor or simulator that was used to collect the observation data of the corresponding offering. This includes the cali- bration at the time of collection, but also the sensor location and eventually attitude. This information represents the lineage of observation data i.e. what happened to the real phenomenon during the sampling and detecting stages of the measurement process and is directly usable for processing of the observation data. It is typically used for deriving meaningful values from the raw observation data as well as geo-locating the measure- ments. 48 Copyright © 2008 Open Geospatial Consortium, Inc. All Rights Reserved.

8.6 Data Processing using SensorML

SensorML can be used very easily to process observation data coming from an SOS. A catalog service will provide the entry point to look for a higher level products, such as geolocated observations or products derived from measurements of several sensors. The- se derived product have traditionally been available on a server where they have been pre-computed. SensorML enables on-demand processing on the client side by providing a detailed process chain that can be applied to existing data in order to derive more useful information. The next sequence shows how a specific SensorML process can be discov- ered and executed by the client using generic SensorML software. The process itself can involve a call to one or more SOS in order to obtain the source data. Advantages of such a mechanism are that only exactly the desired data need to be requested and processed, and that the process can be tweaked to meet exact needs. SOS CS Consumer Processing SOS data using a SensorML Process Chain SensorML Process Search for derivable products GetObservation OM Observation GetRecords SensorML Processing Engine starts Process Chain involves an SOS call SensorML Software processes the data on the fly Copyright © 2008 Open Geospatial Consortium, Inc. All Rights Reserved. 49

8.7 Subscribing and Receiving Sensor Alerts