Linking geodata: Maps Images, Sensors…


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Sumit Sen talks on how various forms of data are getting integrated with Geospatial, and what challenges holds for the developer community.

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Linking geodata: Maps Images, Sensors…

  1. 1. Linking geodata: Maps Images, Sensors… Sumit Sen GIS Development Pvt Ltd
  2. 2. Developing applications with geodata  Are geospatial data related applications special?  Querying and Reporting geospatial data  Connecting to multiple sources  Sensors -> Sensor Observation Services  Vector data -> Web Feature Services  Raster data -> Web Coverage Services  Role of Application Schemas  Synchronisation efforts
  3. 3. Web Services Architecture WSDL UDDI Service Registry Publish Find Web Web Server Browser Service Service Provider Consumer Bind
  4. 4. The Sensors Registered sensor and observation metadata CSW Metadata for a sensor and observations, and a URL Metadata for a sensor observations, and a URL Metadata for a sensor observations, and a URL Metadata for a sensor observations, and a URL Metadata for a sensor observations, and a URL ……… Mission SPS Control System  WNS SWE Architecture SOS Observations & Measurements SensorML Transducer Markup Language (TML)  WAS ! IEEE 1451
  5. 5. Geospatial is not GIS Catalogue of WFS/WMS  Catalogue of Sensor Observation Services  Synchronous data  Networks  Access control  DRM  Design and Engg  Remote Sensing  Imagery  … 
  6. 6. Example
  7. 7. Querying Geospatial data  Form Based (Textual Query)  Translated to SQL easily  Map Based (Pictorial Query)  Translated via Bounding Box or otherwise  Uses spatial operators  Not necessarily same as database operations  Quick views, Redundancy  GeoRSS, GeoSync
  8. 8. Lets remove the simplification here  Points are moving  Attribute values keep on changing  Observations are not made by agents which are spatially dynamic  Buffers are required  Intermediate steps
  9. 9. Geospatial Report  Map based  Textual  Hybrid
  10. 10. Some Strategies  A basic strategy is to redraw changes as data is updated i.e., when a newly positioned object is created or moved. This is acceptable for smaller throughputs but, when the number of objects and data rate increase, system resources can be entirely consumed.
  11. 11. Alternative  An alternative approach to improve performance, presentation graphics can be updated in a cache over time and then pushed to the screen at pre- determined intervals in a single step.
  12. 12. Layer update strategies  In a solution that enables geospatial rendering based on content and time, layering and combining the different strategies can improve both performance and user acceptance.  This allows different sources of data to be updated using the optimal update strategy and then combined for the total picture.  The rendering solution should be able to determine the caching capability to optimize presentation layers - such as map layers and reference graphics— that do not update frequently. This allows developers to create static reference graphics as well as a range of dynamically updating graphics and mix them into a single picture.
  13. 13. And…Distribute across multiple threads  With multiple, layered update strategies, the solution should separate the layers across multiple threads. This allows developers to create data-handling threads between the communication middleware and the rendering on the display.  Number of threads can then be optimized based on the hardware architecture and expanded as technology expands.  This also allows the solution to prioritize threads and ensure that user interaction is responsive.
  15. 15. Getting Data from Sensors  First Step:  Get information about the SOS and the offered data  Second Step:  Get additional information about the procedures, which produce the observations  Third Step:  Get information about the target features of the observations  Fourth Step:  Get the observations from the SOS through different ways
  16. 16. Step1: Get information about the SOS and the offered observations  We want to know temporal and spatial extent of the offered observations as well as meta information about the SOS  Send GetCapabities request to the SOS  Two possibilities:  HTTP GET request  HTTP POST request
  17. 17. Step 2: Request Procedure Metadata  URNs of procedures are listed in capabilities operationsMetadata and Contents sections  To retrieve further informations about a specific sensor, you can use the DescribeSensor Operation  Parameters of DescribeSensor Operation:  service (mandatory) and version (mandatory)  procedure (mandatory)  URN from capabilties document  outputFormat (mandatory)  could be text/xml;subtype=„sensorML/0.0.0 or text/xml;subtype=„TML/1.0.0“  52north‘s SOS water NRW offers only SensorML descriptions
  18. 18. Step 3: Request Metadata about the target features of the observations We know the URNs of the target features for each observation  offering from the contents section of the SOS capabilities document Get additional information as:   name  description  feature location GetFeatureOfInterest operation  only HTTP POST  getFeatureOfInterest operation offers two possibilities to  access feature information: either by feature ids or  by a spatial filter 
  19. 19. Step 4: Request observations  Now get the observations from the stations  use the GetObservation operation for requesting observations from a SOS  GetObservation operation offers flexible filtering options:  Observations for specific phenomena  Observations produced by specific procedures  Spatial filter  Temporal filter  Observation value filter  Combinations of the different filters
  20. 20. WFS / WMS  Standard interfaces  Pull based web services  Serves vector  Needs a Schema file?  Mapping of Schemas  Replication of data  Combining data  SRS consistencies
  21. 21. WCS  Images are not only background  Source for updates to data  Updation, change detection applications  Corrections  Relatively easy to combine multiple sources  For different places?
  22. 22. What about the entities we speak about? Are they consistent  Application Schemas  Have conflict across domains  Mediator/mapping is necessary  Any progress is good – no conflicts  Application Schemas from UML  Transportation example
  23. 23. Synchronisation  Minimise conflicts  Maximise efficiency  Marshalling  Java, …  Replication  Non availability of a service  Quality of Service  Service ranking
  24. 24. Major issues  Applications are heterogeneous  Adding complexity  Applications using applications  Service chains  Value addition  AJAX and Web 2.0 or Web 3.0  Transforming geospatial experiences
  25. 25. Summary  Geospatial data provides unique challenges to developers  Cuts across domains  Multi user environment  Web Services  Sensors, Mapping, Imagery  Applications that a pervasive, ubiquitous
  26. 26. Thank you for your attention