Today, there are hundreds of millions of Internet-connected sensors on, in and around the Earth, and the number is growing rapidly. At the Chair of Geoinformatics, Technical University of Munich (TUM) the modeling and handling of sensor data has been a topic of research and education in the past year. Most of the work we do in that field is based on the OGC's Sensor Web Enablement (SWE) standards suite. A popular open source implementation of the SWE standards is the Sensor Observation Service (SOS) developed by the 52°North Initiative for Geospatial Open Source Software GmbH.
This repository contains example requests for the 52°North SOS for registering new sensors to the service and adding observations for them. Moreover, some general information on how to use these requests with the 52°North SOS client and how to send them from the command line is provided. The repository has been created for educational purpose but may be helpful for anybody involved with the 52°North SOS implementation. Each request is stored and documented in a separate folder. Navigate to the folder of the request you are looking for to find the documentation and examples.
If you encounter a mistake or have a suggestion what we could add or improve, please let us know and post an issue.
In order to receive/send data from/to an SOS instance so called requests are used. The 52°North SOS come with a SOS client, that makes it easy to edit and send requests. Please find a simple example on how to work with the client below.
The SOS client can be accessed using the following link: http://mysos.de:8080/52n-sos-webapp/client
This client can be used to send requests and perform the SOS operations. As shown in the image below, the parameters for the SOS operations can very easily be provided in the requests. Upon selecting the appropriate parameters, the client provides the example requests which can be used to learn for making our own requests. Once the request with correct parameter and syntax is created, it can be sent to the service by clicking on the Send button. The response message can be visualized in the client accordingly. In case of errors, the client will show the error message.
Simply use the dropdown menus to select a service, version, binding and operation. After that, use the Load example request dropdown, to select the example request you want to load. It is recommended to copy the example request shown now in the client to a text editor (e.g. Notepad++) and work on the request offline. Whenever you want to test your request copy it back to the client window and press the Send button to transmit it.
Note: It is not possible to send transactional requests with a transactional authorization token using this client, as it is not possible to edit the HTTP header of the request. Please take a look at the curl folder if you want to use transactional operations!
Besides using the built in client of the 52°North SOS, as described above, SOS requests can be send from a Unix shell as well. If you want to automize request for e.g. sheduled uploading of SOS requests to a SOS server, this is the way to go. Please find some examples on how to do that with the CURL utility in the curl folder.
Before beginning to perform SOS operations, please learn about all the SOS requests in the SOS operations overview. Once you are familiar with the SOS operations and the supported bindings, you are ready to create your own requests.
In order to register your sensor and the sensor observations in the SOS, please adapt the following example requests to your own needs.
If you are missing any information for a request, run a GetCapabilities request and search the answer for the specific operation you want to perform.
This operation allows clients to retrieve service metadata from a service instance.
For instance, GetCapabilities can be used to query for a list of sensors associated with the SOS or all allowed operations.
It also helps in forming the right encodings and parameters for specific operations.
The GetCapabilities request can be made using the SOS client by simply selecting the right parameters. However, it is also possible to make this request using Key Value Pair(KVP) encoding, where all request content is encoded in the URL.
All request parameters are appended to the SOS service URL as KVPs. The first KVP is separated from the service URL with a ?.
All further KVPs are appended with a &, as shown in the examples below:
-
SOS Service URL: http://mysos.de:8080/52n-sos-webapp/service
-
KVPs
- request=GetCapabilities
- service=SOS
- version=2.0.0
-
Resulting request URL:
http://mysos.de:8080/52n-sos-webapp/service?request=GetCapabilities&service=SOS&version=2.0.0
The basic request with no additional parameters but service and version lists the complete capabilities of the SOS. However, it is possible to retrieve only specific sections by providing additional parameters, as listed in the table below:
| Request content | KVPs |
|---|---|
| Details on the service provider | request=GetCapabilities&service=SOS&Sections=ServiceProvider |
| List of possible operations supported by the service and their metadata, showing which encodings are supported by each operation | request=GetCapabilities&service=SOS&version=2.0.0&Sections=OperationsMetadata |
| Filter Capabilities | request=GetCapabilities&service=SOS&version=2.0.0&Sections=FilterCapabilities |
| Entire content of the SOS | request=GetCapabilities&service=SOS&version=2.0.0&Sections=Contents |
Before inserting new observations, it is necessary to add the new sensor to your SOS instance first.
A new sensor can be registered using the InsertSensor operation.
It allows defining the sensor properties and metadata such as sensor location, procedures, offerings, observation properties (e.g. temperature, humidity) and unit of measurement for each property.
Please find an InsertSensor SOAP example request and further documentation in the InsertSensor folder.
Once the sensors are registered, the sensor metadata can be retrieved using the DescribeSensor operation.
This operation is used for requesting information about sensor such as sensor location, procedures, offerings, observation properties (e.g. temperature, humidity) and unit of measurement for each property.
The response of this operation is encoded in a OGC Sensor Model Language (SensorML) instance document.
Please find further documentation in the DescribeSensor folder.
Once the sensor is registered to the SOS, its observations can be inserted. The observation offering can be specified for the sensor, to which the observations can be uploaded in the running SOS. There are two ways to insert the observations:
The InsertObservation operation allows the client to insert new observations for a sensor system.
The request includes the details of the sensor, the observed property, the time of the observation, and its respective property.
Please find further documentation in the InsertObservation folder.
The InsertObservation operation allows inserting only one observation per request.
Hence, it is required to create a single requests for each observations, which can be cumbersome.
In order to make this process simpler, the 52° North SOS provides the InsertResultTemplate and InsertResult operations,
using which, multiple observations can be inserted without having the need to provide all parameters everytime.
Please find further documentation in the InsertResult folder.
The GetObservation operation is designed to query the service for observation data structured according to the Observation and Measurement (O&M) specification.
The request can be made by setting up parameters such as specific procedure, offering, and observedProperty.
In addition, it is also possible to query the observations based on filters such as:
- temporalFilter: A filter for a time property of the requested observations
- spatialFilter: A filter which applies to a spatial property of an observation
Please find further documentation in the GetObservation folder.