Transcript Internet GIS - Geon

GIS on the Web
Opportunity in Webbased Mapping
• Disaster relief and
Emergency management
• Global and national
geospatial information
infrastructures
• Digital Earth, NSDI,
GSDI
• Crime management
• Environmental Monitoring
• Many others...
World Wide Web
Clients
Internet
Servers
Email
FTP
Web Mapping Defined
Web servers and map
viewer clients interact to Catalog
Integrated View
• Discover, access and
retrieve views from
multiple servers
• Display multiple layers
of geographic data within
a single web application
Parcels
Whoville
Roads
Images
Boundaries
...
Whoville
Cedar Lake
Internet
• Query and update
• Provide interface for
visualization, Decision
Support, etc.
View
Environment
• Support geocoded raster,
vector, matrix, and other data
Federal
Program
Social
Services
Crime
Framework
(Clearinghouse) Weather
Land
Parcel
Mapping on the Web
Today
How can I combine data from each of these
sources to answer my question?
What is the OpenGIS?
• Open GIS 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:
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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 nonvoting 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
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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)
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 or
Western Australia:
http://atlas.walis.wa.gov.au/servlet/com.esri.wms.Esrimap?ServiceName=WA_Atlas_GN_WMS&Format=image/PNG&
WMS - getCapabilties
• allows the server to advertise what it can
do:
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available layers
supported output projections
supported output formats
scale hints
extent of data
• XML format
DNR Photo Server (capabilities)
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
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
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
WFS: Web Feature Service
• WFS 1.0 approved 2002
• ISO has requested it be submitted
• Scope: storage & retrieval of geographic
vector 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
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GetCapabilites
DescribeFeatureType
GetFeature
Transaction
LockFeature/GetFeatureWithLock
• Response to GetFeature request is formatted
using GML
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 WFS
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.
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
GML: Geography Markup Language
• GML defines a data encoding in XML that allows
geographic data and its attributes to be moved between
disparate systems with ease
• GML separates content from presentation.
• One of the major breakthroughs with GML is that, when
used with XML tools, GML makes it possible to resolve
many of the difficulties associated with incompatible
data models.
• It is not difficult to create profiles of GML, and this is
what most data developers will do. The Ordnance Survey
of Great Britain and the US Census Bureau (in its TIGER
data) have committed to GML.
• Similar to ArcXML
Basics
• 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
The Three Architecture Cases
The Graphic Element Case
The Picture 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, “singleattribute” 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
<?xml version="1.0"?>
4534,1745 4534,1856 4622,1856 4711,1856 4800,1856 4893,1855
4984,1855
<html xmlns:v="urn:schemas-microsoft-com:vml"><head><style>v\:*
<!DOCTYPE
svg PUBLIC "-//W3C//DTD SVG 20000303 Stylable//EN"{ behavior:
5075,1854 5075,1749 5076,1646 </c></r>
url(#default#VML); }</style>
"http://www.w3c.org/2000/svg10-20000303-stylable"
[
<r><name>Gaslamp</name><URL></URL><labelpos>44.60,83.00</labelpos><c>5
...
<!ENTITY
base
"fill:#ff0000;stroke:#000000;stroke-width:1;">
162,1013 5084,1057 5083,1116 5081,1222 5079,1326 5079,1433 5076,1540
<v:shape id="a1" class=z style="left:0;top:0;width:11590;height:7547"
]>
5076,1646 5075,1749 5075,1854 5167,1854 5257,1855 5257,1750
5259,1647
fillcolor="#FFFF99"
strokecolor="#000000"
strokeweight="1"
<svg
width="100%" height="100%"
viewBox="0
0 11590 7547"title="Horton
style="shape-Plaza"
5260,1541 5262,1434 5262,1328 5263,1222 5263,1013 </c></r>
path="m5076,1540l
4986,1540
4895,1539
4803,1539
4715,1539
rendering:geometricPrecision; text-rendering:optimizeLegibility">4622,1539
...
4534,1538
4534,1641
4534,1745 4534,1856
4622,1856
4711,1856 4800,1856
<g
id="karta"
transform="scale(1,
-1) translate(0,
-7547)">
4893,1855
5075,1854 5075,1749 5076,1646xe"/><v:shape id="a2"
<g
id="base"4984,1855
style="&base;">
class=z
style="left:0;top:0;width:11590;height:7547"
fillcolor="#FFFF99"
<path id="a1" title="Horton Plaza" style="fill:#00ff00;"
d="M5076,1540L 4986,1540
strokecolor="#000000"
strokeweight="1"
path="m5162,1013l
4895,1539
4803,1539 4715,1539
4622,1539title="Gaslamp"
4534,1538 4534,1641
4534,1745
5084,1057
5083,1116
5081,1222
5079,1326
5079,1433
5076,1540
5076,1646
4534,1856 4622,1856 4711,1856 4800,1856 4893,1855 4984,1855 5075,1854
5075,17495076,1646
5075,18545076,1540z"/>
5167,1854 5257,1855 5257,1750 5259,1647 5260,1541
5075,1749
5262,1434
5262,1328
5263,1222
5263,1013xe"/> d="M5162,1013L 5084,1057
<path
id="a2"
title="Gaslamp"
style="fill:#ffff00;"
.5083,1116
..
5081,1222 5079,1326 5079,1433 5076,1540 5076,1646 5075,1749
<div class=label
style="top:75.51%;
left:39.46%;">Horton
Plaza</div><div
5075,1854
5167,1854
5257,1855 5257,1750
5259,1647 5260,1541
5262,1434
class=label
style="top:81%;
left:42.6%;">Gaslamp</div>
5262,1328 5263,1222 5263,1013 5162,1013z"/>
</g></g></svg>
SVG
VML
XML encoding of geographic
features (such as GML)
Rendering
Or
SVG markup
(such as VML)
Some Web Viewers
• Multi-View:
• http://geo.sdsc.edu/website/SIO_Expl/
• Multi-service:
• http://dotnet.sdsc.edu/website/htmlviewer/MultiService/
• AxioMap:
• www.regionalworkbench.org