GIS on the Web;web sources of GIS data

Web Mapping DefinedWeb servers and map Web servers and map viewer clients interact to - viewer clients interact to -

Whoville

WhovilleCedar Lake

Integrated View

Internet

• Display multiple layers Display multiple layers of geographic data within of geographic data within a single web applicationa single web application

• QueryQuery and update and update

• Provide interface for Provide interface for visualization, Decision visualization, Decision Support, etcSupport, etc..

• Support geocoded raster, Support geocoded raster, vector, matrixvector, matrix, and other , and other datadata

• Discover, access and Discover, access and retrieve views from retrieve views from multiple serversmultiple servers

Crime

Social Services

LandParcel

FederalProgram

Weather

Environment

ParcelsRoadsImagesBoundaries ...

CatalogView

Framework(Clearinghouse)

Mapping on the WebMapping on the Web

TodayToday

How can I combine data from each of theseHow can I combine data from each of these

sources to answer my question?sources to answer my question?

Web Services for Generating SVG Tiny Maps

on Mobile Phones

J2ME device

Java + Batik

Viewers:TinyLineSquiggleAdobe’s ASV

Services for generating object textures for Torque

.Net + C#

Torque-GIS

Demo

SAN DIEGO SUPERCOMPUTER CENTER, UCSD

SciR&D

Metadata• Needed to automate the process of search

for data– compare using a library catalog

• Needed to determine the fitness of a data set for use– particularly regarding quality

• Needed to handle data effectively– e.g., format

• Needed to identify notable data contents– e.g., to find images of an interesting hurricane

SAN DIEGO SUPERCOMPUTER CENTER, UCSD

SciR&D

Metadata can be Expensive to Generate

• They represent a high level of abstraction– and may need an expert to define

• But the benefits are substantial– metadata make it possible to find data

sets, and use them effectively– they allow the benefits of investments in

data to be realized

SAN DIEGO SUPERCOMPUTER CENTER, UCSD

SciR&D

The U.S. FGDC Standard

• Content Standards for Digital Geospatial Metadata (CSDGM)

• Defined by a committee of U.S. Federal agencies

• Now widely used worldwide• The basis of a new international standard• Potentially several hundred items for one data

set– but easily boiled down to a much smaller number

SAN DIEGO SUPERCOMPUTER CENTER, UCSD

SciR&D

The Dublin Core Standard

• Devised by the digital library community

• Suitable for any type of data, geospatial included– easily extended to include essential items for

geospatial data– e.g., the latitude and longitude limits of the

data set’s coverage

SAN DIEGO SUPERCOMPUTER CENTER, UCSD

SciR&D

Online

SAN DIEGO SUPERCOMPUTER CENTER, UCSD

SciR&D

The data

portal

SAN DIEGO SUPERCOMPUTER CENTER, UCSD

SciR&D

Interactive access to HIS digital library

SRB (ADOs)

REST/SOAP APIsMetadata (mif, mtf)

CuahsiLink

Hydroviewer

NWIS

Matlab ArcGIS Excel Web browser

Application services: analysis, mapping, charting, models,workflow, integration (8)

Data registration/Search/Query rewriting & orchestration.(6)

NAWQA STORET . . .

Digital Library

External data resources registryDL metadata

We b

ser

vices

regi

stry

and

rela

ted

serv

ices

(10)

DL serviceslayer (5)

Fortran/C/VB/Java codes

PoP Node PoP Node

Core grid services: monitoring nodes, scheduling,data transfer, replication, collectionmanagement,…(1)

Resource drivers (2)

Service consumers

User registration/authentication/authorization (9)portal

SensorsSensors SensorsSensors

Sensor management services (3)

Sensor data filtering (4)

Ontology source andservices (7)

RServer

ArcGIS Server

Conversion engine

Certificateauthority

PoP Node PoP Node

USGS: National Mapping

US GeoDataftp access to

DEMDLGGNIS

GIRASetc.

NOAA: Weather and other data

Why build an SDI?

• Build data once and use it many times for many applications

• Integrate distributed providers of data: Cooperative governance

• “Place-based management”• Share costs of data creation and

maintenance• Support sustainable economic,

social, and environmental development

Types of geospatial standards Data Classification

e.g., Vegetation Classification

Data Content e.g., Digital Geospatial Metadata, Spatial Schema

Data Symbology or Presentation e.g., Digital Geologic Map Symbolization

Data Transfer Data Services (Web Mapping, Feature) Data Usability

e.g., Geospatial Positioning Accuracy

What is the OpenGIS?

• Open Geospatial Consortium (OGC) • Non-profit, international voluntary consensus standards organization• Industry, government, and university members

• Over 260 members worldwide – 30 countries & 5 continents• 91 European members - 19 countries• 35 Asia-Pacific members - Japan, Republic of Korea, Australia, China, and

Thailand

• OGC collaborates and works closely with:• International Organization for Standardization (ISO) • World Wide Web Consortium (W3C)• OASIS• And others…

OGC Membership Levels

• OGC members participate at four levels:• Associate: Commercial and university members granted non-

voting participation in Technical Committee, and full access to OGC technical documents.

• Technical: participate and vote in OGC Technical Committee, creating the OpenGIS® Specifications in Special Interest and Working Groups.

• Principal: participate and vote in OGC Technical and Planning Committees, providing management of OGC Specification Program and Interoperability Program and guides OGC Technology Roadmap and Interface Development Schedule.

• Strategic: highest level of OGC membership, voting in both the OGC Technical Committee and the OGC Planning Committee and receive additional benefits from the Consortium based on a specific business plan jointly developed with OGC.

Approved Specifications

• Simple Feature Access – OLE, SQL, CORBA• Catalog 1.1.1• Coordinate Transformation 1.1• Grid Coverages 1.0• Web Map Service 1.1.1 (2.0 in final edit) (WMS)• Geography Markup Language 3.0 (GML) 529 pages alone!!!• Web Feature Service 1.0• Filter 1.0• Style Layer Descriptor 1.0 (SLD)• Web Coverage Service 0.0 (WCS)• OpenLS• OGC Web Services (Ongoing)• Web Map Client Configuration

WMS: Web Map Service• Mature, well-established specification

• Version 1.0 issued 2000-04• Version 1.1.1 issued 2001-12• Server & client support in many vendor products &

freeware

• Scope: geographic data rendered as images ("maps"),not actual data values• Similar to ArcIMS Image Server

Demo: see lifemapper.org orWestern Australia: http://atlas.walis.wa.gov.au/servlet/com.esri.wms.Esrimap?ServiceName=WA_Atlas_GN_WMS&Format=image/PNG&

OGC Web Map Service Interfaces

• GetCapabilites

• GetMap

• GetFeatureInfo

WMS - getCapabilties

• allows the server to advertise what it can do:• available layers• supported output projections• supported output formats• scale hints• extent of data

• XML format

WMS - getMap

• allows the retrieval of a map from a web server

• user supplies bounding box, image size, format, error handling, etc…

• server responds with an “image”, typically a web-ready format like GIF, PNG or TIFF

GetMap Request Example

• http://b-maps.com/map.cgi?VERSION=1.1.0&• REQUEST=GetMap&• SRS=EPSG:4326&• BBOX=-97.105,24.913,78.794,36.358&• WIDTH=560&• HEIGHT=350&• LAYERS=BUILTUPA,COASTL,POLBNDL&• STYLES=0XFF8080,0X101040,BLACK&• FORMAT=image/png&• BGCOLOR=0xFFFFFF&• TRANSPARENT=TRUE&

WMS – getFeatureInfo

• allows the retrieval of simple feature attributes

• user supplies an x,y coordinate pair and a layer of interest

• server responds with attribute information in HTML, GML or arbitrary ASCII format

• … optional interface

WMS Limitations

• all you get is a picture, not the data• limited control over how the data is

“styled”• particularly limiting with regards to labeling• supports only a small portion of

functionality typically supported by a vendor

Style Layer Descriptor enabled Web Map Service

• In a basic WMS style is “just a name” that identifies a specific layer portrayal

• An SLD WMS adds the ability to control layer style

• An SLD WMS adds the following additional operations that are not available on a basic WMS:• DescribeLayer• GetLegendGraphic• GetStyles• PutStyles

• These interfaces are described in the SLD specification document

WFS: Web Feature Service

• WFS 1.0 approved 2002• ISO has requested it be submitted

• Scope: storage & retrieval of geographicvector feature data (point/line/polygon)• Hydrography, Transportation, Government Units,

Cadastral, Geodetic Control• Similar to ArcIMS Feature Server

OGC Web Feature Server Interfaces

• OGC WFS Interfaces• GetCapabilites• DescribeFeatureType• GetFeature• Transaction• LockFeature/GetFeatureWithLock

• Response to GetFeature request is formatted using GML (typically)

Two classes of WFS

Basic WFS

A basic WFS would implement the GetCapabilities, DescribeFeatureType and GetFeature operations. This would be considered a READ-ONLY web feature service.

Transaction WFS

A transaction web feature service would support all the operations of a basic web feature service and in addition it would implement the Transaction operation. Optionally, a transaction WFS could implement the LockFeature operation.

Basic WFS

GetCapabilities

A web feature service must be able to describe its capabilities. Specifically, it must indicate which feature types it can service and what operations are supported on each feature type.

DescribeFeatureType

A web feature service must be able, upon request, to describe the structure of any feature type it can service.

GetFeature

A web feature service must be able to service a request to retrieve feature instances..

Transaction

A web feature service may be able to service transaction requests. A transaction request is composed of operations that modify features; that is create, update, and delete operations on geographic features.

LockFeature/GetFeatureWithLock

A web feature service may be able to process a lock request on one or more instances of a feature type for the duration of a transaction.

Transaction WFS

DescribeFeatureType

• Generates a schema definition for the requested features using the language specified in the capabilities document (XML schema is mandatory, others are optional)

• The XML schema document must be a valid GML application schema and defines the schema of the feature types listed in the request.• Feature geometry must be expressed using the GML geometry

description.• Spatial Reference Systems must be consistent with GML

GetFeature

• The GetFeature operation allows retrieval of features from a web feature service.

• The request contains queries which may unconstrained or constrained by a Filter

• Filter is described in described in the Filter Encoding Specification

• The output format is GML by default but the specification allows other formats

Basics of GML• Geography Markup Language (GML) is an XML

grammar written in XML Schema for the modeling, transport, and storage of geographic information.

• GML provides a variety of kinds of objects for describing geography including features, coordinate reference systems, geometry, topology, time, units of measure and generalized values.

• GML includes• Geometries and Coordinate Reference System (based on

EPSG)• A temporal reference system (based on ISO 8601)• A Units of Measure (UOM) dictionary

GML 3.0

• GML models various resources required to describe geospatial information:• Features (including coverages and observations).• Coordinate Reference Systems• Units of Measure• Values (as values of feature properties)• Topology and Geometry (as values of feature properties)• Temporal (as values of feature properties)

The Three Architecture Cases

The Picture CaseThe Graphic Element Case The Data Case

(source: OpenGIS document 99-077)

Architectures for Different Applications

• Each map request sends new geometry:• Examples: find by address or another attribute; routing, “single-attribute”

maps, weather maps, etc.• In general: situations when geometry is defined by attribute (categorical

coverages, for example)

• Geometry remains relatively constant:• Examples: atlases, statistical maps for collection zones (states, counties,

census tracts)• In general: situations with many attributes for limited number of

geometries

• For the latter case: makes sense to cache and re-use coordinate information on the client side as much as possible. For each application, there is some right mix of the two approaches.

From Geography Markup to Rendering<?xml version="1.0" encoding="iso-8859-1"?><rs><r><name>Horton Plaza</name><URL></URL><labelpos>41.46,77.51</labelpos><c>5076,1540 4986,1540 4895,1539 4803,1539 4715,1539 4622,1539 4534,1538 4534,1641 4534,1745 4534,1856 4622,1856 4711,1856 4800,1856 4893,1855 4984,1855 5075,1854 5075,1749 5076,1646 </c></r><r><name>Gaslamp</name><URL></URL><labelpos>44.60,83.00</labelpos><c>5162,1013 5084,1057 5083,1116 5081,1222 5079,1326 5079,1433 5076,1540 5076,1646 5075,1749 5075,1854 5167,1854 5257,1855 5257,1750 5259,1647 5260,1541 5262,1434 5262,1328 5263,1222 5263,1013 </c></r>. . .XML encoding of geographic features (such as GML)

<html xmlns:v="urn:schemas-microsoft-com:vml"><head><style>v\:* { behavior: url(#default#VML); }</style>. . .<v:shape id="a1" class=z style="left:0;top:0;width:11590;height:7547" fillcolor="#FFFF99" strokecolor="#000000" strokeweight="1" title="Horton Plaza" path="m5076,1540l 4986,1540 4895,1539 4803,1539 4715,1539 4622,1539 4534,1538 4534,1641 4534,1745 4534,1856 4622,1856 4711,1856 4800,1856 4893,1855 4984,1855 5075,1854 5075,1749 5076,1646xe"/><v:shape id="a2" class=z style="left:0;top:0;width:11590;height:7547" fillcolor="#FFFF99" strokecolor="#000000" strokeweight="1" title="Gaslamp" path="m5162,1013l 5084,1057 5083,1116 5081,1222 5079,1326 5079,1433 5076,1540 5076,1646 5075,1749 5075,1854 5167,1854 5257,1855 5257,1750 5259,1647 5260,1541 5262,1434 5262,1328 5263,1222 5263,1013xe"/>. . .<div class=label style="top:75.51%; left:39.46%;">Horton Plaza</div><div class=label style="top:81%; left:42.6%;">Gaslamp</div>

Rendering markup (such as VML)

VML

<?xml version="1.0"?><!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 20000303 Stylable//EN" "http://www.w3c.org/2000/svg10-20000303-stylable" [<!ENTITY base "fill:#ff0000;stroke:#000000;stroke-width:1;">]><svg width="100%" height="100%" viewBox="0 0 11590 7547" style="shape-rendering:geometricPrecision; text-rendering:optimizeLegibility"><g id="karta" transform="scale(1, -1) translate(0, -7547)"><g id="base" style="&base;"><path id="a1" title="Horton Plaza" style="fill:#00ff00;" d="M5076,1540L 4986,1540 4895,1539 4803,1539 4715,1539 4622,1539 4534,1538 4534,1641 4534,1745 4534,1856 4622,1856 4711,1856 4800,1856 4893,1855 4984,1855 5075,1854 5075,1749 5076,1646 5076,1540z"/><path id="a2" title="Gaslamp" style="fill:#ffff00;" d="M5162,1013L 5084,1057 5083,1116 5081,1222 5079,1326 5079,1433 5076,1540 5076,1646 5075,1749 5075,1854 5167,1854 5257,1855 5257,1750 5259,1647 5260,1541 5262,1434 5262,1328 5263,1222 5263,1013 5162,1013z"/></g></g></svg>

Or SVG

SVG

layers appearing in the initial view

layers which users can show and hide

base thematic layer

optional polygon layers

optional line layers

optional point layers

base area labels

graphics (labels, buffers)

foreground polygon layers n 1 0

n 1 0

n 1 0

n 1 0

background layers n 1 0

cosmetic elements in a view

foreground point layers n 1 0

foreground line layers n 1 0

Map StructureMap

Structure

<svg id="axiomap" onload="initMap(evt)" onmousemove="GetElementAndPosition(evt)" onmousedown="set_menu()" . . . >

<rect id="canvas" fill="white" stroke-width="0" x="0" y="0" width="100%" height="100%"/>

<desc></desc> <defs>

<menu id="MENU" xmlns="http://foo"> <header>Custom Menu</header>

. . .</menu>

</defs>  <g id="map"

style="stroke-linejoin:round; stroke-linecap:round"> <g id="background_polygons"/> <g id="base_thematic"/>

<g id="foreground_polygons "/><g id="optional_polygons "/><g id="foreground_lines"/><g id="optional_lines"/><g id="foreground_points"/><g id="optional_points"/><g id="cosmetic"/>

 <g id="tooltips"

style="shape-rendering:optimizeSpeed">. . . </g>

  <g id="stable_gui_elements“

style="shape-rendering:optimizeSpeed"> <g id="map_title" style="visibility:visible"> . . . </g> <g id="layer_navigation_group"> . . . </g> <g id="legend" style="visibility:hidden" . . .> . . . </g>

. . . </g> </g> <g id="extras"></g></svg>

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