8.1 GIS Hardware and Software 8.1 GIS Hardware and Software 8.2 Hybrid vs. Integrated Systems 8.3 Client/Server Systems

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8 Architecture of Geographic Information Systems

8.1 GIS Hardware and Software 8.1 GIS Hardware and Software 8.2 Hybrid vs. Integrated Systems 8.3 Client/Server Systems

8.4 Web-based Spatial 8.4 Web-based Spatial

Databases

8.5 Summary

(2)

8 Architecture of GIS

• A geographic information system is a system

designed to collect, manage, analyze, display spatial data

data

• Specialized information system that consists of

– Spatial database, – Spatial database,

– Spatial database system, – Application Software – Application Software

• Often end users only see

• Often end users only see specially programmed

user interface

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8 Architecture of GIS

• Environmental information system

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8 Architecture of GIS

• Tourist information system

(5)

8 Architecture of GIS

• Urban planning information system

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8 Architecture of GIS

• Network information system

(7)

8.1 GIS Hardware and Software

• GIS hardware mainly differs from "normal"

information systems in the input devices

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8.1 GIS Hardware and Software

• Input device: digitizer

– Collection of coordinates

– Magnifying glass with crosshairs – Magnifying glass with crosshairs – Electronic pen

– Electromagnetic

surface http://www.uni-

surface

– Digitization of maps

http://www.uni-

potsdam.de/Geographie/

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8.1 GIS Hardware and Software

• Input device: drum scanner

– Oldest type of scanner – Provides accurate results – Provides accurate results – Usually with very high

resolution

– Original on a rotating drum

http://www.at-mix.de/

– Original on a rotating drum – Scanning device always in the

same position to the original same position to the original

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8.1 GIS Hardware and Software

• GIS-Software

– Components (user-oriented view)

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8.1 GIS Hardware and Software

•

Classification of GIS software

•

Classification of GIS software

– Expert GIS

standard GIS, spatial data server, geodatabase

– Desktop-GIS – Desktop-GIS

data management for collection and information

– Mobile GIS – Mobile GIS

information, collection, updating

– Web-GIS – Web-GIS

information, usually no collecting and updating

– Component GIS

embedding GIS functionality into third party systems

– Component GIS

embedding GIS functionality into third party systems

– GIS-Viewer

software for displaying and querying GIS data formats software for displaying and querying GIS data formats

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8.2 Hybrid vs. Integrated Systems

• Architecture of GIS can be roughly classified

– File based – Hybrid – Hybrid

– Layer-oriented – Integrated

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8.2 Hybrid vs. Integrated Systems

• File based architecture

– First generation of GIS (since approx. 1960) – All information stored in files

– All information stored in files – No logical data independence – No physical data independence – No standardization

– No standardization

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8.2 Hybrid vs. Integrated Systems

•

Hybrid architecture

•

Hybrid architecture

– Relational databases are used for thematic attributes – Spatial data is stored

– Spatial data is stored

in specific data structures on files

– Consistency of the data is difficult to ensure

ensure

– Queries which

combine thematic and combine thematic and spatial attributes are not possible

not possible

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8.2 Hybrid vs. Integrated Systems

• For example, a query which is not possible with

• For example, a query which is not possible with hybrid architecture (see section 4.5)

SELECT b1.id

FROM Building b1, Building b2 WHERE b1.typeOfUse = ’church’

AND AND

b2.typeOfUse = ’car park’

AND

Distance(Centroid(b1.groundPlan),

• Attention: sometimes the term "hybrid GIS"

Distance(Centroid(b1.groundPlan),

Centroid(b2.groundPlan)) < 2000;

• Attention: sometimes the term "hybrid GIS"

also is used for such systems, able to integrate vector and raster data

vector and raster data

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8.2 Hybrid vs. Integrated Systems

• Layer-oriented architecture

– Thematic attributes and spatial data are stored in one single (relational) are stored in one single (relational) database

– Spatial data are modeled as relations – Spatial data are modeled as relations – Introduction of a layer with

geometric functions

– Inefficient access to individual spatial – Inefficient access to individual spatial

objects (have to be collected by means of joins)

means of joins)

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8.2 Hybrid vs. Integrated Systems

• Example of relational modeling of polygons as a

• Example of relational modeling of polygons as a list of points (see section 4.3)

– Id attribute, list position and integer attributes x, y – Id attribute, list position and integer attributes x, y – For each polygon the values of

position have to start with value 1 position have to start with value 1 and have to be dense

(implementation of a list) (implementation of a list)

CREATE TABLE Polygons ( CREATE TABLE Polygons (

id CHAR(20),

position INTEGER,

x INTEGER,

y INTEGER,

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8.2 Hybrid vs. Integrated Systems

• Integrated architecture

– Thematic attributes and spatial data are stored in one single (geographic) database

single (geographic) database – Database functions and GIS

functionality in one system functionality in one system

– Database functions support the processing of spatial data

– Spatial index structures – Spatial index structures – Logical data independence – Standardization possible – Standardization possible

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8.2 Hybrid vs. Integrated Systems

• Example of a query which is possible with

• Example of a query which is possible with integrated architecture;

typically, this query is typically, this query is evaluated by using an

R-tree index (see section R-tree index (see section 4.6 and section 5)

4.6 and section 5)

SELECT p.id

FROM Parcel p, FROM Parcel p, Brook b

WHERE intersects (p.groundPlan, b.geometry);

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8.2 Spatial Join

• Relational join algorithms aren’t applicable for

• Relational join algorithms aren’t applicable for spatial joins (except Nested Loop)

– Sort-Merge-Join – Sort-Merge-Join

matNr result

1005 4.0

matNr firstName

1005 Clark 1005 4.0

1005 1.3

2832 5.0

1005 Clark

2832 Lois

4512 Lex 2832 5.0

5119 1.7

8676 1.3

5119 Charles

6676 Erik

8024 Jean

– No order on spatial (multi-dimensional) data

9876 3.7

8024 Jean

– No order on spatial (multi-dimensional) data

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8.2 Spatial Join

– Hashjoin – Hashjoin

0 1

0

matNr firstName 1 matNr result

1 2 3

1 2 3 1005 Clark

2832 Lois

4512 Lex

9876 3.7

2832 5.0

1005 4.0

4 5 6

4512 Lex

5119 Charles

6676 Erik

1005 4.0

1005 1.3

6676 1.3

6 7

6676 Erik

8024 Jean

6676 1.3

5119 1.7

– A hash function, which assigns the same value to extended, overlapping objects is not known

extended, overlapping objects is not known

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8.2 Spatial Join

• Spatial join using r-trees

– Suppose the height of both r-trees is the same

– Only MURs on the same level have to be checked for – Only MURs on the same level have to be checked for intersections and only if their parent’s MURs intersect – A priority queue is used to store the node pairs which

have to be checked

– Filter step of the spatial query evaluation

→ results have to be validated using the original

→ results have to be validated using the original geometry of the objects

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8.2 Spatial Join

procedure INDEX_TRAVERSAL_SPATIAL_JOIN(rootA, rootB) begin

priorityQueue ← CREATE_PRIORITY_QUEUE();

priorityQueue.ADD_PAIR(rootA, rootB);

while NOT priorityQueue.EMPTY() do nodePair ← priorityQueue.POP();

nodePair ← priorityQueue.POP();

rectanglePairs ← FIND_INTERSECTING_PAIRS(nodePair);

foreach p Є rectanglePairs do if p is a pair of leaves then if p is a pair of leaves then

REPORT_INTERSECTIONS(p);

else

priorityQueue.ADD_PAIR(p);

endif;

enddo;

end; http://doi.acm.org/10.1145/1206049.1206056

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8.2 Spatial Join

• ADD-PAIR

– Defines the order in which the priority queue is processed

processed

• Breadth first search

• Breadth first search with additional ordering of the nodes

• Breadth first search with additional ordering of the nodes on one level i.e. x-coordinate or z-address of the MUR’s center

center

• Depth first search

1 1

1

2 3 4

1

2 5 8

(25)

8.2 Spatial Join

• Example

3 8

a

j 2

3 8

b 9

c d

k j

1 4

5

6

c d

e

l 5

7 f

g h

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8.2 Spatial Join

• R-tree of the rivers

a j

b

c d

k j

l

c d

e

l

f

g h

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8.2 Spatial Join

• R-tree of the rivers

I II

A B C D E a

j C

I

h i

b

c d

k j

l A

B

C

a c

b d e j k l

f g c d

e

l

b d e j k l

f

g D E h

i II

(28)

8.2 Spatial Join

• R-tree of the woods

3 8

1

2

3

4

9

1 4

5

6

7

(29)

8.2 Spatial Join

• R-tree of the woods

III IV

3 8

III IV

F G H I

2

3

4

8 9 F

G IV I

F G H I

8 9

1 4

5

6 1 2 F

3 4

8 9

5

7 H

5 6 7 III

(30)

8.2 Spatial Join

• 1. iteration

– nodePair: (rootA, rootB)

– priorityQueue: ((II,III) (I,IV) (I,III)) – priorityQueue: ((II,III) (I,IV) (I,III))

I

IV

III

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8.2 Spatial Join

• 2. iteration

((E,H) (D,H) (I,IV) (I,II))

• 2. iteration

– nodePair: (II, III)

– priorityQueue: ((E,H) (D,H) (I,IV) (I,II)) – priorityQueue:

F

G F

D H

E

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8.2 Spatial Join

• 3. iteration

((i,7) (h,7) (D,H) (I,IV) (I,II))

• 3. iteration

– nodePair: (E,H)

– priorityQueue: ((i,7) (h,7) (D,H) (I,IV) (I,II)) – priorityQueue:

5

6

h 7

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8.2 Spatial Join

I II III IV

C A B D E H G F I

a c b d e h i

j k l f g 5 6 7 3 4 1 2 8 9

(34)

8.2 Spatial Join

• FIND_INTERSECTING_PAIRS

procedure PLANE_SWEEP(listA, listB)

begin 5 6

begin

statusA ← CREATE_STATUS() statusB ← CREATE_STATUS()

while NOT listA.END() OR NOT listB.END() do if listA.FIRST() < listB.FIRST() then

f g

5

7 if listA.FIRST() < listB.FIRST() then

statusA.INSERT(listA.FIRST())

statusB.REMOVE_INACTIVE(listA.FIRST()) statusB.SEARCH(listA.FIRST())

listA.NEXT()

statusA:

listA.NEXT() else

statusB.INSERT(listB.FIRST())

statusA.REMOVE_INACTIVE(listB.FIRST()) statusB:

statusA.REMOVE_INACTIVE(listB.FIRST()) statusA.SEARCH(listB.FIRST())

listB.NEXT() endif

enddo

statusB:

enddo

(35)

8.3 Client/Server Systems

•

Cooperating components

•

Cooperating components

– Client initiates the communication – Client sends requests to the server – Server provides a fixed set of services – Roles and functions are asymmetric

– Sequence of interaction steps is determined – Sequence of interaction steps is determined – Client may access

multiple servers multiple servers – Server may serve

multiple clients multiple clients

– Server may also be client when

processing a request processing a request

(36)

8.3 Client/Server Systems

• Various kinds of realising client/server systems

• The differences arise as a result of the partitioning of total functionality

partitioning of total functionality

• Possible sub-functions

– Presentation – Presentation

function

– Application – Application

function – Data

– Data

management function

function

(37)

8.3 Client/Server Systems

• In the GIS area there are several alternatives how to assign sub-functionalities to clients and to servers

• Typical functions of a GIS client

– Data acquisition, digitization – Data acquisition, digitization – Transformations

– Functions for image processing – Functions for image processing – Basic CAD functions

– Constructing of spatial objects – Constructing of spatial objects

– Data reduction, smoothing, generalization – User interface

http://www.ikg.uni-hannover.de/

– User interface

– Presentation of data – Data output

– Data output

(38)

8.3 Client/Server Systems

• Typical functions of a GIS server

– Selection of thematic and spatial information from geographic

information from geographic data base

– Preview of selected spatial data – Preview of selected spatial data – Conversion of selected spatial

data into the appropriate target format

– Cartographic representation of selected spatial data

selected spatial data

(39)

8.3 Client/Server Systems

•

The main services of a GIS server (in the web) were

•

The main services of a GIS server (in the web) were defined by the Open Geospatial Consortium (OGC, see section 6.3)

see section 6.3)

– Web Coverage Service (WCS)

Selection of raster data and its meaning – Web Feature Service (WFS)

Exchange of spatial objects (features) – Web Map Service (WMS)

– Web Map Service (WMS) Selection of maps

derived from derived from raster or

vector data vector data

(40)

8.3 Client/Server Systems

•

Web Coverage Service (WCS)

•

Web Coverage Service (WCS)

– A coverage is multidimensional (usually 2-dimen-dimensional) (usually 2-dimen-dimensional) image of a space-related

phenomenon (also called "field", see section 2.4)

see section 2.4)

– Enables modeling and

representation of an actual representation of an actual distribution of values in space – WCS operations are

– WCS operations are

• GetCapabilities

• DescribeCoverage

(41)

8.3 Client/Server Systems

•

GetCapabilities

•

GetCapabilities

– Describes the services provided by the WCS server – Indicates what coverages are available

– Indicates what coverages are available

•

DescribeCoverage

– Provides detailed – Provides detailed

information about a coverage

a coverage

•

GetCoverage

– Provides a coverage or a subset of a coverage – Provides a coverage or a subset of a coverage – Also specifies the

output format output format

(42)

8.3 Client/Server Systems

•

Web Feature Service (WFS)

•

Web Feature Service (WFS)

– Exchange of spatial objects with vector geometries – Requests are sent as a

– Requests are sent as a

HTTP request from a client to the WFS

– WFS offers the following operations

• GetCapabilities

• DescribeFeatureType

• GetFeature

• Transaction

• LockFeature

(43)

8.3 Client/Server Systems

• GetCapabilities

– Describes which WFS services are available – Gives the names of the available feature types – Gives the names of the available feature types

• DescribeFeatureType

– Describes the schema of a feature type – Describes the schema of a feature type

• GetFeature

<wfs:Query

typeName="AX_Gebaeude">

<ogc:Filter>

• GetFeature

– Delivers an instance of a feature

typeName="AX_Gebaeude">

<ogc:Filter>

<ogc:PropertyIsEqualTo>

<ogc:PropertyName>

weitereGebaeudefunktion

– Supports spatial and non-spatial selections

weitereGebaeudefunktion

</ogc:PropertyName>

<ogc:Literal>1170</ogc:Literal>

</ogc:PropertyIsEqualTo>

</ogc:Filter></ogc:PropertyIsEqualTo>

</ogc:Filter>

(44)

8.3 Client/Server Systems

•

Web Map Service (WMS)

•

Web Map Service (WMS)

– Request/transmission of visual representations of spatial information (maps)

– Supports three functions – Supports three functions

• GetCapabilities

• GetMap

• GetFeatureInfo (optional)

•

GetCapabilities

•

GetCapabilities

– Provides metadata in XML format – General information about the

provider provider

– Available output formats

– Available maps and their layers – Available maps and their layers

(45)

8.3 Client/Server Systems

• GetMap

– Provides map – Several options

• Map layers

• Presentation of the layers

• Underlying coordinate system

• Map window

• Size of the map

• Output format

• GetFeatureInfo (optional)

– Information about spatial objects on the map – Thematic attributes, usually in XML format – Thematic attributes, usually in XML format

(46)

8.4 Web-based Spatial Databases

• Collection of spatial data is particularly expensive

• Spatial data is durable

• Geoservices are increasingly offered by the

• Geoservices are increasingly offered by the internet

• Typical keyword: "Internet GIS"

– Internet GIS applications reach – Internet GIS applications reach

many users

– Requirement for internet clients are low

– Standards enable simple exchanges

exchanges

(47)

8.4 Web-based Spatial Databases

• Application areas of internet-GIS

– Simple information systems

• Standard internet environment with usual plug-ins

• Presentation of interactive maps

• E.g. in the local area for publication of information to

• E.g. in the local area for publication of information to citizens and

visitors visitors

(48)

8.4 Web-based Spatial Databases

– Specialized georeferenced information systems – Specialized georeferenced information systems

• Additional services to the public or for a restricted group of people

people

• Dynamical systems needed, since data is processed during request

request

• E.g. address search, route planner

(49)

8.4 Web-based Spatial Databases

– Web-based GIS clients with access to key resources – Web-based GIS clients with access to key resources

• Offer advanced functionalities

• Analysis and intersection of spatial data

• Export and update of attributes

• Used mostly in spatial data infrastructures, because user

• Used mostly in spatial data infrastructures, because user training is required

– Portals for spatial data – Portals for spatial data

• For providing and selling of large quantities of data

quantities of data

• Usually data is supplied by different spatial data servers

spatial data servers

(50)

8.4 Web-based Spatial Databases

• Internet GIS components

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8.4 Web-based Spatial Databases

• Technical options for internet GIS

setting server client remark

statical websites

HTML documents, graphic objects

web browser proven feasible and easy solution

interactive websites

HTML documents, graphics objects, extensive embedded functionalities

web browser with script support

needed for larger amounts of and changing selections of data client HTML documents with web browser with with high demands on

client

application

HTML documents with

embedded software components, data files

web browser with plug-ins such as SVG, Java, special viewer

with high demands on

presentation, scalability, and interaction

dynamic dynamic server application, direct web browser independence from the client, dynamic

websites

dynamic server application, direct access to spatial data

web browser independence from the client, large amounts of data, and a variety of functions

spatial data data services which provide spatial client, for access to distributed spatial spatial data

infrastructure

data services which provide spatial data via pre-defined interfaces

spatial client, for example, viewer, web portal, desktop GIS

access to distributed spatial databases

terminal high performance server with special client full access to a desktop GIS via terminal

server

high performance server with terminal suite, GIS software, and

special client full access to a desktop GIS via internet

(52)

8.5 Summary

• GIS to collect, manage, analyze, display spatial data

– Specialized information system

– Spatial database, spatial database system – Spatial database, spatial database system – Application software

• GIS hardware and software

– Special input devices – Special input devices – Digitizer

– Drum scanner – Drum scanner

– Classification of GIS software – Classification of GIS software

(53)

8.5 Summary

• Hybrid vs. integrated systems

– File based architecture – Hybrid architecture – Hybrid architecture

– Layer-oriented architecture – Integrated architecture

– Integrated architecture

– Detour [spatial join with R-tree index]

• Client/server Systems

– Various kinds of realising client/server systems – Various kinds of realising client/server systems – Typical functions of a GIS client

– Typical functions of a GIS-server – Typical functions of a GIS-server

(54)

8.5 Summary

– Web Coverage Service (WCS) – Web Coverage Service (WCS) – Web Feature Service (WFS) – Web Map Service (WMS) – Web Map Service (WMS)

• Web-based spatial databases Web-based spatial databases

– Internet GIS

– Application areas of internet GIS – Application areas of internet GIS – Internet GIS components

(55)

8.5 Summary

software system

architectures

hardware

architectures

internet

GIS client/

GIS

GIS client/

server