Upload
harsha-vardhan-madiraju
View
761
Download
0
Tags:
Embed Size (px)
DESCRIPTION
Sumit Sen talks on how various forms of data are getting integrated with Geospatial, and what challenges holds for the developer community.
Citation preview
Linking geodata: Maps Images, Sensors…
Sumit Sen
GIS Development Pvt Ltd
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
Web Services Architecture
Service
Registry
Service
Provider
Service
Consumer
PublishPublish FindFind
BindBind
WebWeb
BrowserBrowser
UDDIUDDIWSDLWSDL
WebWeb
ServerServer
The Sensors
SP
SS
OS
WN
SW
AS
CS
W
Mission
Control
System
Registered sensor and observation metadata
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………
!
SWE Architecture
Observations & Measurements
SensorML
Transducer Markup Language
(TML)
IEEE 1451
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 …
Example
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
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
Geospatial Report
Map based
Textual
Hybrid
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.
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.
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.
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.
GPS
GPS
GPS
APPLICATION
SOS
SOS
SOS WFS
WFS
WCS
Example - routing
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
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
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
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
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
WFS / WMS
Standard interfaces
Pull based web services
Serves vector
Needs a Schema file?
Mapping of Schemas
Replication of data
Combining data
SRS consistencies
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?
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
Synchronisation
Minimise conflicts
Maximise efficiency
Marshalling
Java, …
Replication
Non availability of a service
Quality of Service
Service ranking
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
Summary
Geospatial data provides unique challenges to developers
Cuts across domains
Multi user environment
Web Services
Sensors, Mapping, Imagery
Applications that a pervasive, ubiquitous
Thank you for your attention