Spatial Data and Geographic/Spatial Databases

Vania Bogorny www.inf.ufsc.br/~vania [email protected]

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 2

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

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What is Spatial/Geographic data?

• 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; 4

How are spatial data represented?

• Points, Lines, Polygons, and complex geometries.

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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 6

Spatial Representation: field

Irregular points (e.g. temperature) Regular Points Isoline (e.g. relief) Adjacent polygons (e.g. soil) Grid célula Triangual Network(e.g. ) 7

Example: Geographic Data and Geographic Database

Street Gid

1 2

Name

Ijui Lavras

Shape

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

WaterResource Gid

1

Name

Jacui 2 3 Guaiba Uruguai

Shape

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

GasStation Gid Name VolDiesel VolGas Shape

1 BR 2 IPF 20000 85000 Point[(x1,y1)] 30000 95000 Point[(x1,y1)] 3 Esso 25000 120000 Point[(x1,y1)] 8

Example of geographic data Districts are represented as green polygons Slums are represenetd as yellow polygons Water bodies are represented as blue lines 9

Example of geographic data Districts, Squares and Trees 10

Example of geographic data Districts and Slums 11

Example of geographic data Districts and Hospitals 12

Overlay of Geographic Data Combination of some previous data 13

Maps as Layers

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Spatial Relationships

• Main characteristic which differs spatial data from non-spatial data 15

Viaduct intersects road OR Road crosses viaduct District contains soccer field Disjunção

16

Crosses relationship

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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) ?

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Spatial Relationships

Which is the closest put to my house?

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Main Spatial Relationships Topological B

touches

Order Distance

north

A 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

Examples of Spatial Operations Original Polygons Union Intersection 23

Rivers Examples of Spatial Operations Buffered Rivers 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 S WHERE 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 pass?

select r.name,c.cntry_name from river r, country c where crosses (r.the_geom,c.the_geom) = 'True' Rainy Rainy name | cntry_name ---------------------------------+-------------- Pembina | United States Pembina | Canada | United States | Canada Souris Souris | United States | Canada Red River of the North | United States Red River of the North | Canada (8 rows)

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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) 28

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: •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

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Exercicios

1) Escreva uma consulta que conte as pracas do bairro Botafogo 2) Escreva uma consulta que retorne as favelas do bairro Tijuca mostre o resultado no mapa 3) Escreva uma consulta que retorne os rios que cruzam o bairro Barra da Tijuca 4) Escreva uma consulta que retorne as Favelas que contem escolas, mostrando-as no mapa 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

) 3.

4.

5.

6.

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.

2.

7.

Download suitable spatial datasets in shapefile format from ESRI's web-site : Convert shapefiles into sql files shp2pgsql [] [.]

> sqlfilename.sql Example: shp2pgsql c street.shp street_table my_db > street.sql http://www.esri.com/data/download/basemap/index.html Import the sql files into PostGIS psql [options]... [dbname [username]] Example: psql -d my_db -f country.sql 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 Try spatial queries. Following are example of spatial queries from chapter 3 of the Spatial Database book. • Query: List the names of the capital cities in the CITY table ( script ) • • Query: Find the names of all countries which are neighbors of the United States (USA) in the Country Table ( Query: For all the rivers listed in the River table, find the countries through which they pass ( script ) script ) • • Query: Which city listed in the City table is closest to each river listed in the River table? ( Query: List the name, population, and area of each country listed in the Country table ( script script ) 8.

• Query: List the length of the rivers in each of the countries they pass through ( script ) 31 One may consider taking the results of a query back to Arc Explorer for visualization using pg2shp.exe converter available with postgis software.

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:

GIS. San Francisco: Morgan Kaufmann, 2002.

With Application to SHEKHAR, S., CHAWLA, S.

Spatial databases

: a tour

.

Prentice Hall, 2003.

Upper Saddle River, NJ: OPEN GIS CONSORTIUM.

Topic 5, the OpenGIS abstract specification – OpenGIS features –Version 4.

1999a. Available at .

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 32