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Week 5 - Module 3 - GIS and Services Oriented Architectures

Overview ### {.module03a01a}

  • Geographic Information Systems
    • Data Types
    • Coordinate Systems
  • Services Oriented Architectures
    • Historic Context
    • Current Model - Network Computing
    • Components
    • Interoperability Standards

Geographic Information Systems ## {.module03a01a}

Data Types - Vector ### {.module03a01a}

  • Vector data represent phenomena that are associated with specific bounded locations, typically represented by:

    • Points
    • Lines
    • Polygons

  • Vector data include:

    • The geometries that describe the area being referenced, and
    • Attributes associated with that area

For example, a census vector data product might include the geometries that define census tracts and attributes associated with each geometry: population, income, etc.

Data Types - Raster ### {.module03a01a}

  • Raster data are frequently used to represent values for phenomena that vary continuously across space (e.g. elevation, concentration of air pollutants, depth to ground water, etc. )

  • These values are encoded over a regular grid of observation locations with a specified grid spacing - often referred to as the spatial resolution of the dataset (i.e. 10m resolution for a standard USGS Digital Elevation Model product)

  • Often parts of data collections that are repeated (i.e. remote sensing data products)

Accessing and Processing Raster and Vector Data

  • ArcGIS - ArcCatalog
  • QGIS - Dataset properties available through the "Metadata" tab
  • Through metadata files available from the provider web site or embedded in the downloaded file

Accessing and Processing Raster and Vector Data - Programmatically ### {.module03a01a}

  • Two geospatial libraries and their related utility programs provide information about and tools for modifying vector and raster data sets

OGR : vector data access and information

GDAL : raster data access and information

These libraries are the data access and processing foundation for a growing number of open source and commercial mapping systems

Information and documentation: GDAL Home Page | OGR Home Page

Coordinate Systems/Projections ### {.module03a01a}

  • To convert locations from a 3-dimensional oblate spherical coordinate system (such as is commonly used to represent the surface of the earth) to a 2-dimensional representation in a map, a coordinate transformation must be performed.
  • There are a limitless number of potential coordinate transformations possible, and a large number have been named and defined that meet specific cartographic or other requirements

EPSG Codes ### {.module03a01a}

  • A catalog of numeric codes and associated coordinate transformation parameters is maintained by the International Association of Oil & Gas Producers (OGP) - the successor scientific organization to the European Petroleum Survey Group (EPSG)

  • These numeric codes are used by many desktop and online mapping systems to document and represent the coordinate systems of available data and services

  • Links to an online version of the registry and downloadable databases of the registry are available from: http://www.epsg.org/Geodetic.html.

Projection Parameters ### {.module03a01a}

The parameters that define a map projection may be looked up in a number of online locations:

EPSG registry : Helpful if you already know the EPSG code of the projection you are looking for - http://www.epsg-registry.org/

GeoTIFF Projection List : Helpful if you know the name of one of the broadly used projections - uneven performance of links - http://www.remotesensing.org/geotiff/proj_list/ [Archived Version]

SpatialReference.org : Decent search tool, includes non-EPSG as well as EPSG projection information, multiple descriptions of projection parameters - http://spatialreference.org/

Services Oriented Architectures ## {.module03a01a}

Where have we come from - ENIAC (1946) ### {.module03a01a .oneUp}

ENIAC Computer{.oneUp}

  • First general purpose electronic computer
  • Programmable, but could not store programs

Where have we come from - Early Client-Server Computing (1960s) ### {.module03a01a .threeUp}

IBM 704 Mainframe Computer{.threeUp}

Model 33 ASR Teletype{.threeUp}

TeleVideo 925 ASCII Terminal{.threeUp}

  • Mainframe computers to which client terminals connected over a local network
  • Computing performed by server, client purely a display device

Where have we come from - Personal Computers (1970s) ### {.module03a01a .twoUp}

IBM 5150 Personal Computer{.twoUp}

Apple I Personal Computer{.twoUp}

  • Desktop computers capable of running a variety of operating systems and applications
  • In some environments can be interconnected to a central local server

Now - Network computing ### {.module03a01a .oneUp}

World Internet Hosts 1/94-1/13. Image courtesy IWS - http://www.isc.org/services/survey/{.oneUP}

Network Computing Timeline ### {.module03a01a}

  • Predecessor to the Internet - ARPANET (1969). Interconnection between UCLA and SRI (Menlo Park)
  • Adoption of TCP/IP as next generation protocol for ARPANET (1983)
  • NSF commissions construction of NSFNET, also based upon TCP/IP (1983)
  • NSFNET opened to commercial connections (1988). Led to interconnection of multiple, previously separate networks into an “Internet”
  • Growth of internet users has expanded rapidly over the past decade

In a Phrase ... ### {.module03a01a}

The current networking computing model consists of Components Interacting with Each Other

So - We Need to Answer the Following Questions ### {.module03a01a}

What are components?

What does it mean to interact?

The Big Picture - Services Oriented Architectures ### {.module03a01a .floatLeft}

SOA Illustration

  • Services Oriented Architecture (SOA) for Geospatial Data and Processing
    • Data, Processing & Client Tiers
  • Open Geospatial Consortium Interoperability Standards
    • WMS, WFS, WCS
  • Geospatial Metadata Standards
    • ISO 19115, FGDC
  • Internet Standards
    • Web: HTML, CSS, JavaScript, XML
    • SOAP - Simple Object Access Protocol
    • REST - Representation State Transformation

The Pieces - Components ## {.module03a01a}

Key Components - Data ### {.module03a01a}

Database systems

  • Optimized for storing massive quantities of tabular data
  • May be spatially enabled to support the storage of geometries (points, lines, polygons) in addition to related attribute data
  • Standard language (Structured Query Language [SQL]) for interacting with many databases
  • Broad support for accessing the contents of databases from many other applications and programming languages, for example:
    • Spreadsheets
    • Statistical Software
    • Geographic Information Systems (GIS)

Key Components - Data ### {.module03a01a}

File-based data

  • Often stored on the file system
  • Sometimes difficult represent data within a database structure (i.e. binary data)
  • May be in a wide variety of formats
    • XML
    • ASCII Text (e.g. CSV, tab-delimited)
    • Binary files
    • Excel Spreadsheets
    • Word Processing Documents
    • Geospatial data (e.g. imagery)
  • Remotely Accessible Data
    • Some data may be provided through reference to an external network resource (i.e. a web address, or other identifier) or service

Key Components - Processing Services### {.module03a01a}

  • Perform modification of source data to generate a new data product

  • May be “chained” together to create a processing “workflow”. Output from one processing service may be used as the input to another

  • May be simple OGC services; or complex data processing, analysis, or visualization services. Examples include

    • Extraction of a subset of a large data set based upon provided search criteria
    • Generation of a map from a collection of data
    • Fusion of two data products into a single derived product (e.g. vegetation indices calculated from multiple remote sensing images)
    • Calculation of statistical information for an input product, and delivery of the statistical summary

Key Components - Clients ### {.module03a01a}

  • Any system that accesses the services provided by the system may be considered a “client”
  • That system may be manually operated by a human user, or triggered automatically by software
  • Human operated clients include
    • Web-based applications
    • Desktop applications such as Geographic Information Systems and Statistical Analysis tools
  • Machine clients include
    • Data processing services that translate requests to them into requests for other system services
    • Regularly scheduled requests that are automatically triggered by external computer systems.

The Glue - Interoperability Standards / Service Interfaces ## {.module03a01a}

Open Geospatial Consortium Interoperability Standards ## {.module03a01a}

Open Geospatial Consortium (OGC) Standards ### {.module03a01a}

  • Two Classes of Standards Considered Here
    • Geospatial Product Access Standards
    • Geospatial Data and Representation Standards
  • Product Access Standards
    • Web Map Services (WMS)
    • Web Feature Services (WFS)
    • Web Coverage Services (WCS)
  • Data and Representation Standards
    • Geography Markup Language (GML)
    • KML (formerly known as Keyhole Markup Language)

Comparison of OGC Service Models ### {.module03a01a .center}

Comparison of OGC Service Models

OGC Web Map Services (WMS) ### {.module03a01a .oneUp}

WMS request result for Bernalillo County Landsat Mosaic from NM RGIS link

http://gstore.unm.edu/apps/rgis/datasets/
b030ab7b-86e3-4c30-91c0-f427303d5c77/
services/ogc/wms?
	VERSION=1.1.1&&
	SERVICE=WMS&
	REQUEST=GetMap&
	SRS=EPSG:4326&
	FORMAT=image/jpeg&
	STYLES=&
	LAYERS=bernalillo_tm2011&
	TRANSPARENT=TRUE&
	WIDTH=521&
	HEIGHT=200&
	bbox=-107.207,34.8404,-106.143,35.2487

OGC Web Feature Services (WMS) Characteristics ### {.module03a01a}

  • HTTP GET (required), HTTP POST (optional)
  • Requests:
    • GetCapabilities
    • GetMap
    • GetFeatureInfo
  • Returns
    • Mapped data
    • XML Capabilities Document, Feature Attributes
  • Includes support for time-based requests

OGC Web Feature Services (WFS) Characteristics### {.module03a01a}

  • Either HTTP GET or POST required
  • Requests
    • GetCapabilities
    • DescribeFeatureType
    • GetFeature/GetFeatureWithLock
    • GetGmlObject
    • LockFeature
    • Transaction
  • Returns
    • XML (GML)
    • Capabilities
    • Feature Data

OGC Web Coverage Services (WCS) Characteristics### {.module03a01a}

  • Either HTTP GET or POST required
  • Requests
    • GetCapabilities
    • DescribeCoverage
    • GetCoverage
  • Returns
    • Geospatial data for coverage
    • XML Capabilities
  • Includes support for time-based requests

OGC Geography Markup Language (GML) ### {.module03a01a}

  • GML is an XML grammar for representing geospatial features and their associated attributes
  • In its generic form it can encode points, lines, and polygons and their associated attributes
  • As an XML schema GML was designed to be extensible by communities of practice for consistent encoding of geographic data more richly than allowed by the generic default model
  • GML documents representing large complex geometries can be quite large - therefore slow to transfer over the Internet

OGC KML ### {.module03a01a}

  • An XML specification that supports the encoding of representation and embedding of geospatial data for use in geospatial viewers
  • Began as the underlying representation language of Google Earth (originally developed by Keyhole for their virtual Earth viewer)
  • Adopted as an OGC standard in 2008
  • Supports data linkage through
    • Embedding
    • Reference through external URLs - with WMS specifically supported through parameterization
  • Includes support for the representation of time in relation to data objects

Implementation of the OGC Standards ### {.module03a01a .twoColumn}

  • WMS

    • 1.3.0 - 389 implementations
    • 1.1.1 - 558
    • 1.1 - 263
    • 1.0 - 301

  • WFS

    • 2.0 - 78
    • 2.0 transactional - 17
    • 1.1.0 - 310
    • 1.1.0 transactional - 83
    • 1.0.0 - 363
    • 1.0.0 transactional - 131

  • WCS

    • 2.0 - Core - 7
    • 1.1.2 - 27
    • 1.1.1 Corregendum 1- 67
    • 1.1.0 - 30
    • 1.0.0 Corregendum - 227

  • KML

    • 2.2.0 - 117
    • 2.2 Reference (Best Practice) - 11
    • 2.1 Reference (Best Practice) - 82

  • GML

    • 3.3 - 6
    • 3.2.1 - 157
    • 3.1.1 - 161
    • 3.0 - 156
    • 2.1.2 - 179
    • 2.1.1 - 127
    • 2.0 - 82
    • 1.0 - 20

Implementation information based upon OGC Implementation Statistics - Accessed 2/2017

OGC Summary ### {.module03a01a}

The OGC web service specifications support key geospatial data access requirements

WMS : visualization of geospatial data through simple web requests

WFS : delivery of geospatial data (typically points, lines, and polygons) in a format that is usable in GIS and other applications

WCS : delivery of geospatial data (typically, but not limited to, raster data) usable in other applications

OGC Summary ### {.module03a01a}

The OGC data and representation standards support data exchange and higher level representation

GML : XML schema for the representation of features and associated attributes. It may be extended for use by specific communities of users (i.e. ecological data models)

KML : XML schema that supports the combination of embedded data and external data into a complete representation model that may be used by client applications to present the data through a user interface (e.g. Google Earth, WorldWind)