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

Sumit.sen@gisdevelopment.net