Spatial Data and Geographic/Spatial Databases

Vania Bogorny

www.inf.ufsc.br/~vaniavania@inf.ufsc.br

2

What is a Spatial/Geographic Database?

Database that:

• Stores spatial objects

• Provides operations to manipulate spatial objects

• Manipulates spatial objects just like other objects in the database

3

What is Spatial/Geographic data?

• Data which describes a location or a shape

e.g. House, Hospital, Road, River, Forests, Parks, Soil

• Is something that describes objects or phenomena that happen on the Earth and that have associated a geographic position

4

• Three main characteristics describe a geographic object: Non-spatial attributes (what): describe either quantitatively or

qualitatively a geographic entity. This data may be treated by non-spatial databases;

Spatial attribute (where): refers to the location and the representation of the geographic object, considering geometry and coordinate system. This aspect requires a specific data type not available in conventional DBMS;

Spatial relationships (how): neighbourhood relationships (e.g. topology, distance). Requires special operations that are not available in conventional DBMS;

What is Spatial/Geographic data?

5

How are spatial data represented?

• Points, Lines, Polygons, and complex geometries.

6

Spatial Representation: object

0-dimensional representation: point E.g.: school, hospital,

Uni-dimensional representation: line E.g.: river, road

Bi-dimensional representation: polygon E.g.: state, city

Tri-dimensional representation: surface E.g.:building

7

Spatial Representation: field

célula

Irregular points (e.g. temperature)

Adjacent polygons (e.g. soil)

Regular Points

Grid

Triangual Network(e.g. )

Isoline (e.g. relief)

8

Example: Geographic Data and Geographic Database

Street

Gid Name Shape

1 Ijui Multiline [(x1,y1),(x2,y2),..]

2 Lavras Multiline [(x1,y1),(x2,y2),..]

WaterResource

Gid Name Shape

1 Jacui Multiline [(x1,y1),(x2,y2),..]

2 Guaiba Multiline [(x1,y1),(x2,y2),..]

3 Uruguai Multiline [(x1,y1),(x2,y2),..]

GasStation

Gid Name VolDiesel VolGas Shape

1 BR 20000 85000 Point[(x1,y1)]

2 IPF 30000 95000 Point[(x1,y1)]

3 Esso 25000 120000 Point[(x1,y1)]

9

Districts, Squares and Trees

Example of geographic data

10

Districts and Slums

Example of geographic data

11

Districts and Hospitals

Example of geographic data

12

Combination of some previous data

Overlay of Geographic Data

13

Maps as Layers

14

Spatial Relationships

• Main characteristic which differs spatial data from non-spatial data

15

District contains soccer field

Viaduct intersects road

OR

Road crosses viaduct

Disjunção

Crosses relationship

16

17

Spatial Relationships

What is the average distance between industrial repositories and water collecting points?

18

Spatial Relationships

How distant are water bodies (blue line) from industrial repository

(pink dot) ?

19

Spatial Relationships

Which is the closest put to my house?

20

Main Spatial Relationships

B

C

A

B north A

C southeast A

B

C

A

B north A

C southeast A

OrderDistance

CBd

CBd

BA

touches

A B

overlaps

B

inside

A

contains BA

crosses

A Bequals

A B

BA A B

overlaps

inside

A

contains

A B

disjoint

A B

disjoint

BA

crosses

A Bequals

A BTopological

21

Advantages of Spatial Databases

Spatial querying using SQL– use simple SQL expressions to determine spatial

relationships• distance

• order

• topology

– use simple SQL expressions to perform spatial operations• area

• length

• intersection

• union

• buffer

22

Original Polygons

Union Intersection

Examples of Spatial Operations

23

Rivers

Buffered Rivers

Examples of Spatial Operations

24

Spatial Databases

• ESRI ArcSDE (on top of several different DBs)• Oracle Spatial• IBM DB2 Spatial Extender• Informix Spatial DataBlade• MS SQL Server (with ESRI SDE)• Geomedia on MS Access• PostGIS / PostgreSQL

25

Spatial Query Language• Spatial query language

• Spatial data types, e.g. point, linestring, polygon, …• Spatial operations, e.g. overlap, distance, nearest neighbor, …• SELECT S.name

FROM States SWHERE area(s.the_geom) > 300

• Standards• OGIS is a standard for spatial data types and operators

26

Spatial Query Example

Q1: For all rivers in the relation “River”, which countries do they cross?

select r.name,c.cntry_name from river r, country c where crosses (r.the_geom,c.the_geom) = 'True'

          name          |  cntry_name   ---------------------------------+--------------- Pembina             | United States Pembina             | Canada Rainy                  | United States Rainy                  | Canada Souris                 | United States Souris                  | Canada Red River of the North | United States Red River of the North | Canada(8 rows)

27

Spatial Query Example

Q2: Find the names of all countries which are neighbors of the United States (USA)

select c1.cntry_name as USA_Neighbors from country c1, country c2 where touches(c1.the_geom,c2.the_geom)='True' and 

c2.cntry_name='United States';

 usa_neighbors --------------- Canada(1 row)

Como criar um BDG no PostgreSQL

•1) createdb -E SQL_ASCII -T template_postgis -Uusername nomeDaBase ou criar via PGADMIN•2) importação dos dados geográficos (usar UTF8):

•Transformação dos arquivos shape em .sql (Fazer isso para todos os arquivos .shp)

– a) shp2pgsql -I arquivo.shp nomeDaTabela > tabela.sql

•Importação para o banco de dados:

– b) psql -Uusuario nomeDaBase <tabela.sql

28

Exercicios

1. Escreva uma consulta que mostre o nome dos bairros que contem hospitais

2. Escreva uma consulta que faca um buffer de 100 metros nos hospitais. Mostre no mapa os hospitais e os hospitais com buffer

3. Escreva uma consulta que retorne o nome das vilas que contem hospitais e postos de saude em um entorno de 1000 metros.

4. Escreva uma consulta que retorne o nome dos bairros (atributo do ponto de coleta) que contem pontos de coleta de agua localizados a menos de 500 metros de postos de combustivel ou pocos de residuos industriais

5. Escreva uma consulta que retorne as vilas que contem escolas, mostrando-as no mapa

29

30

Exercise I (http://www.spatial.cs.umn.edu/Book/labs/vania/spatialQueries.html)

Spatial Queries using Postgres/Postgis This exercise demonstrates spatial queries from chapter 3 in Prof. Shekhar's book. using Postgresql/PostGIS SDBMS and a spatial dataset

downloaded from ESRI's web-site. It provides a multi-step process to download spatial datasets, convert those to sql, load into postgres/postgis SDBMS, and run queries. Note that one may skip the first two steps for a quick start using the following sql files: Cities (city.sql, city.gif) Countries(country.sql, country.sql) Rivers (river.sql, river.gif) Water (water.sql, water.gif) Streets (street.sql. street.gif) Each sample .sql file is the converted shapefile ready to import into PostGIS using step 3 of the process. The .gif file is the graphical

representation of the shapefiles, created in ArcExplorer, which is a free software for geographic data visualization. Complete Multi-step Process

1. Download suitable spatial datasets in shapefile format from ESRI's web-site : http://www.esri.com/data/download/basemap/index.html 2. Convert shapefiles into sql files shp2pgsql [<options>] <shapefile> [<schema>.]<table> > sqlfilename.sql Example:

shp2pgsql -c  street.shp  street_table my_db > street.sql 3. Import the sql files into PostGIS psql [options]... [dbname [username]] Example: psql -d my_db -f country.sql 4. After import the data login into Postgresql pgsql my_db Example: (sample session output) • List all tables. Example: sample session. • You may look at the schema and contents of various table using other postgres commands. Example Query: List all cities and the

country they belong to in the CITY table Example Postgis expression and output: script 1. Try spatial queries. Following are example of spatial queries from chapter 3 of the Spatial Database book.

2. Query: List the names of the capital cities in the CITY table (script)

3. Query: Find the names of all countries which are neighbors of the United States (USA) in the Country Table (script) 4. Query: For all the rivers listed in the River table, find the countries through which they pass (script)

5. Query: Which city listed in the City table is closest to each river listed in the River table? (script 6. Query: List the name, population, and area of each country listed in the Country table (script)

7. Query: List the length of the rivers in each of the countries they pass through (script)

2. One may consider taking the results of a query back to Arc Explorer for visualization using pg2shp.exe converter available with postgis software.

31

References• GUTING, R. H. An Introduction to Spatial Database Systems. The International

Journal on Very Large Data Bases, [S.l.], v.3, n.4, p. 357 – 399, Oct. 1994.

• RIGAUX, P.; SCHOLL, M.; VOISARD, A. Spatial Databases: With Application to GIS. San Francisco: Morgan Kaufmann, 2002.

• SHEKHAR, S., CHAWLA, S. Spatial databases: a tour. Upper Saddle River, NJ: Prentice Hall, 2003.

• OPEN GIS CONSORTIUM. Topic 5, the OpenGIS abstract specification–OpenGIS features–Version 4. 1999a. Available at <http://www.OpenGIS.org/techno/specs.htm>.

• OPEN GIS CONSORTIUM. OpenGIS simple features specification for SQL. 1999b. Available at <http://www.opengeospatial.org/docs/99-054.pdf>.

• OPEN GIS CONSORTIUM. Feature Geometry. 2001. Available at <http://www.opengeospatial.org/specs>.