GIS 05 Databases

8/10/2019 GIS 05 Databases

1/60

GIS DATABASES

an overview


2/60

2

Contents

the basics of data storage

overview of databases

the database approach

types of databases

databases in GIS

design considerations

development of an ARC/INFO database


3/60

3

Conceptual, logical and physical ...

Conceptual Logical Physical


4/60

4

A storage hierarchy ...

files/tables

records

fields(types )

databases information systems

decision support systems (DSS)

approaches to storage application/file based

databases

increasingcomplexit

y


5/60

5

Application based approach

Permits

Tax/Rates

AssessmentAssessment Data

Permit Data

Sewer DataSewer

Maintenance

Applicationsusing data stored as Application Specific data


6/60

6

Database approach

Permits

Tax/Rates

AssessmentAssessment Data

Permit Data

Sewer DataSewer

MaintenanceDatabaseManagementSystem

Database approach and use of shared data -

implications for GIS


7/60

7

Database a definition

A collection of interrelateddata stored

together with controlled redundancy to

serve one or more applications in an optimalfashion.

A common and controlled approach is usedin adding new data and modifying and

retrieving existing data within the data base


8/60

8

Databases objectives/advantages

centralised data storage and management

global view of data data dictionary

standardisation of all aspects of data management

reduced duplication

multiple access / retrieval flexibility

integrity constraints validation enforced

...data base management system (DBMS)


9/60

9

Database/s data dictionary

the most critical (?) element of a database

data about data metadata

essential for system developmentuses include

design - entities and data relationships

data capture - entry/validation

operations - program documentation

maintenance (impact assessment of proposed

changes , est. of effort, cost )


10/60

10

Data dictionary

types of information (general)


11/60

GIS Metadata


12/60

12

DBMS key modules

a data description/definition module

defines/creates/restructures

enforces rules

a query module

retrieval for queries, ad-hoc queries, simple reports

a report writing program

a high level language interface

...


13/60

13

Database stages of development

information systems plan for organisation

system specification user needs analysis

conceptual design data modelling hardware and software independent

physical design database design

database implementation

monitoring/audit


14/60

14

Database stages of development


15/60

15

Organisational strategy and IT

Land Information System (LIS) (i)

Problems/issues:

rationalisation of land related information in

government agencies

the removal/reduction of duplication

introduction of economies in data capture,

maintenance and storage

better (and wider) access to data

solutions ...


16/60

16

Organisational strategy and IT

Land Information System (LIS) (ii)

Solutions:

better data distribution mechanism (data format and

location transparent to user)

knowledge of data distribution built into the datadictionary

reduction of data duplication

uniform query language (SQL)

coding and data interchange standardisation (

SDTS)


17/60


18/60

18

Database types -a history

Evolution of Database

technology


19/60

19

Database types - hierarchical (i)

lends itself to GIS use as data are oftenhierarchical in structure e.g. municipality x

province x country

records divided into logically related fields connected in a tree-like arrangement

master field in each group of records pointers updates require pointers to be

modified fast preset queries ad hoc queries difficult or

impossible


20/60

20

Database types

- hierarchical (ii)

COUNTRY (USA)

States

Counties

Boundaries

Nodes


21/60

Hierarchical Structure for a

Cadastral database


22/60

Hierarchical Structure for a

Cadastral database


23/60

23

Database types - network (i)

similar to hierarchical but have multiple

connections between files to accommodate

many to many (M:M) relationships

access to a particular file without searching the

entire hierarchy above that file

linked records quick preset searches large

overhead in pointer managementmodification after creation difficult


24/60

24

Database types - network (ii)


25/60

25

Database types - network (ii)


26/60

26

Database types - relational (i)

model developed from mathematics

records and fields in a 2-dimensional table

no pointers etc any field can be used to link

one table to another

normalisation redundancy/stable structure

ad hoc queries SQL modifications easy

not very efficient for GIS SQL3


27/60

27

Database types - relational (i)


28/60

28

Database types - relational (iii)


29/60

Hierarchical structure

Network structure

Relational structure

(part)


30/60

30

Centralised vs distributed

a database does not necessarily mean a

centralised arrangement i.e. all data in one

physical place


31/60

31

GIS and distributed databases

...trend towards open systems ... special hardware and software can be used widely

specific applications optimised

system/network communications is easier

modular implementation from an overall design

incremental change

unlimited capacity (nodes) lower risks


32/60

32

Approaches to GIS system design

develop a proprietary system

develop a hybrid system: proprietary graphics +

commercial DBMS for attribute data (e.g.

ARC/INFO)

use commercial DBMS and develop spatial

functions and graphics display used in

geographic analysis (e.g. siroDBMS, System9)develop a spatial DBMS from scratch


33/60

33

Approaches to GIS system design


34/60

Software

linkages

(1) Separate Spatial and attribute data

(2) Integrated Spati

and attribute data


35/60

35

GIS databases some problems (i)

centralised risk

centralisation demands better quality control other higher

potential for disaster

cost

large DBMSs are expensive to design, implement and operate

piecemeal design is difficult

complexity

need to keep track of complex hardware and software

need to keep track of graphical as well as attribute data and the

links


36/60

36

GIS databases some problems (ii)

Cascading effects of change in a GIS database (ESRI 1989)


37/60

GIS Design


38/60

38

GIS database design guide


39/60

39

Objectives of design

a good design results in a database which:

contains necessary data but no redundant data

organises data so that different users access the same

data accommodates different views of the data

distinguishes applications which maintain data from

those that use it

appropriately represents, codes and organisesgeographic features


40/60

40

Design methodology (for ARC/INFO)

conceptual model

model the users view

define entities and their relationships

logical model

identify representation of entities

match to ARC/INFO data model

organise into geographic data setsphysical model


41/60

41

Design methodology (for ARC/INFO)

1. Model the users view

2. Define entities and their relationships

3. Identify representation of entities

4. Match to ARC/INFO data model

5. Organise into geographic data sets


42/60

42

1. Model the users view

create a model of work performed by users for

which location is a factor

identify organisational functions

identify the data which supports the functions

organise data into sets of geographic features

data function matrix

high level classification of data

interdependence of data and function

difference between users and creators of data


43/60

43

Land development management function


44/60

44

Data function matrix an example


45/60

45

2. Define entities and their relationships

entities: distinguishable objects which have a

common set of properties

identify and describe entities

identify and describe the relationship among theseentities

document the process

diagrams

data dictionary

Normalise the data


46/60

46

Entity/relationship definition


47/60

47

Diagramming entities


48/60

48

Normalisation

First Normal Form (1NF)

Second Normal Form (2NF)

Third Normal Form (3NF)

ASR - Assessor


49/60

Underlying entities...

Parcel Zoning Owner Ownership


50/60

53

3. Identify representation of entities

determine the most effective spatialrepresentation for geographic features

consider whether:

a feature might be represented on a map the shape of a feature might be significant inperforming geographic analysis

the feature will have different representations anddifferent map scales

textual attributes of the feature will be displayed onmap products

...


51/60

54

4. Match to ARC/INFO data model

determine the appropriate ARC/INFO

representation for entities

points, lines, polygons

ensure complex feature classes are supported

route comprised of sections which in turn are based

on arcs

a region is composed of polygons

event is a point or a line which occurs along a route

others (e.g. GRID, TIN)


52/60

55

Matching to ARC/INFO data model

Entity Spatialtype

ARC/INFO

Relatedto

Coverage Attribute files

Anno.LUT


53/60

56

5. Organise into geographic data sets

to identify and name the geographic data sets

that will contain the various entities:

define the contents of geographic data sets

(coverages, grids etc) name workspaces, geographic data sets, entities and

attributes

complete entity definitions

add cartographic text and lookup tables


54/60

57

5(i) Define the content of geographic data sets

Data sets supported : coverage, grid, tin, image

and drawing

coverages several entities can be grouped into a

single coverage

DBMS : stored in a separate database

management system


55/60

58

5 (ii) Geographic datasets, entities and attributes

coverage definitions

high level summary of the data physically stored in

the database

required for defining the coverage structure

file naming conventions in ARC/INFO


56/60

59

5 (iii) Complete entity definitions

background information: coverage name, data

source, agency, number of records etc.

attribute definition

attribute name, type, field width

validation rules/ permitted values


57/60

60

5 (iv) Cartographic text & code tables

annotation (text, placing rules etc)

look up tables

pre defined set of values

description/ labels

means of creating displays based on attribute values


58/60

61

Robinson (Ch 14): Scale and GIS databases

(past) maps scale greatly influenced map

content and data resolution

GIS data are scaleless scale is still a

critical factor with digital databases - becauseof the ways in which we create digital databases

scale and resolution (Tab 14.1)


59/60

62

Robinson (Ch 14): Scale and resolution issues

symbolisation and display problems

handling databases of different scales

join problems (e.g. urban rural)

merge problems (different themes)

scale levels

in general

large scale data (AM/FM etc.)


60/60

Robinson (Ch 15): Managing large GIS

Data organisation

partitioning

spatial indexes

metadata

data compression

run length encoding (RLE)

quadtree encoding

others ...

Documents

GIS 05 Databases