Geoapplications development

http://rgeo.wikience.org

Higher School of Economics, Moscow, www.cs.hse.ru

Agenda2

Spatial queries: motivating examples3

http://www.spatial.cs.umn.edu/Book/sdb-chap1.pdf

Spatial SQL4

OpenGIS Implementation Specification for Geographic information -Simple feature access - Part 2: SQL option

Spatial database management system (SDBMS)5

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Discussion6

Data platforms map: June 2015, by 451 Research7

PostgreSQL8

PostGIS 9

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http://postgis.net/features/

PostGIS: generic workflow10

Enabling PostGIS11

http://postgis.net/install/

-- Enable PostGIS (includes raster)CREATE EXTENSION postgis;-- Enable TopologyCREATE EXTENSION postgis_topology;-- Enable PostGIS Advanced 3D-- and other geoprocessing algorithms-- sfcgal not available with all distributionsCREATE EXTENSION postgis_sfcgal;-- fuzzy matching needed for TigerCREATE EXTENSION fuzzystrmatch;-- rule based standardizerCREATE EXTENSION address_standardizer;-- example rule data setCREATE EXTENSION address_standardizer_data_us;-- Enable US Tiger GeocoderCREATE EXTENSION postgis_tiger_geocoder;

Enabling PostGIS (2)12

Basic SQL statements13

-- Create table with spatial columnCREATE TABLE geotable (

id SERIAL PRIMARY KEY,geom GEOMETRY(Point, 26910),name VARCHAR(128)

);

-- Add a spatial indexCREATE INDEX geotable_gix

ON geotableUSING GIST (geom);

See next trainings for indexing spatial data

-- Add a pointINSERT INTO geotable (geom) VALUES (

ST_GeomFromText('POINT(0 0)', 26910));

-- Query for nearby pointsSELECT id, nameFROM geotableWHERE ST_DWithin(

geom,ST_GeomFromText('POINT(0 0)', 26910),1000

);

PostGIS at a glance14

Item Description

Spatial data types (for table columns)

geometry, geography, box3d, box2d, spheroid, raster, gidx, topology.TopoGeometry, etc.

Spatial objects (to be stored in table fields)

Defined using POINT(0 0)LINESTRING(0 0,1 1,1 2)

Indexing strategy GiST (Generalized Search Tree)

Functions (loads of them!)

Egenhofer topological relationship, map algebra, other raster operations, etc.

Command line tools

shp2pgsql, pgsql2shp, raster2pgsql, etc.

Formats Vector and raster data export in various formats

Other 3D object, network topology, geocoder/reverse geocoder/(US Census Tiger data)

See previous trainings to revise WKT + its UML, Egenhofer matrix, map algebra, etc.

PostGIS – spatial data types15

<skipped> ………CREATE OR REPLACE FUNCTION geometry_send(geometry)

RETURNS byteaAS '$libdir/postgis-2.2','LWGEOM_send'LANGUAGE 'c' IMMUTABLE STRICT;

-- Availability: 0.1.0CREATE TYPE geometry (

internallength = variable,input = geometry_in,output = geometry_out,send = geometry_send,receive = geometry_recv,typmod_in = geometry_typmod_in,typmod_out = geometry_typmod_out,delimiter = ':',alignment = double,analyze = geometry_analyze,storage = main

);

-- Availability: 1.5.0CREATE TYPE geography (

internallength = variable,input = geography_in,output = geography_out,receive = geography_recv,send = geography_send,typmod_in = geography_typmod_in,typmod_out = geography_typmod_out,delimiter = ':',analyze = geography_analyze,storage = main,alignment = double

);

-- Availability: 0.5.0CREATE TYPE spheroid (

alignment = double,internallength = 65,input = spheroid_in,output = spheroid_out);

PostGIS – spatial objects16

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ST_GeomFromText('POINT(-126.4 45.32)', 26910) -- WKTST_GeomFromEWKT('SRID=26910;POINT(-126.4 45.32)') -- EWKT

Recall EPSG17

PostGIS – spatial objects (2)18

SQL-MM Part 3:• SQL Multimedia Applications Spatial specification• Introduces circularly interpolated curves• not yet fully supported by PostGIS

CIRCULARSTRING(0 0, 1 1, 1 0)CIRCULARSTRING(0 0, 4 0, 4 4, 0 4, 0 0)

More details are at http://postgis.net/docs/manual-2.2/using_postgis_dbmanagement.html

GEOMETRY VS GEOGRAPHY19

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CREATE TABLE global_points (id SERIAL PRIMARY KEY,name VARCHAR(64),location GEOGRAPHY(POINT,4326) -- restrict to store POINTs only and SRID=4326=WGS84

);

INSERT INTO global_points (name, location) VALUES ('London',ST_GeographyFromText('SRID=4326;POINT(0 49)') );

http://postgis.net/docs/manual-2.2/using_postgis_dbmanagement.html

JDBC & PostGIS: before we proceed20

JDBC21

http://www.developersbook.com/jdbc/images/JDBC-Architecture.gif

JDBC & PostGIS22

// Load the JDBC driver and establish a connection.

Class.forName("org.postgresql.Driver");

String url = "jdbc:postgresql://localhost:5400/postgis_example";

java.sql.Connection conn = DriverManager.getConnection(url, "postgres", "1111");

// <skipped adding PostGIS types to connection> -- see course site for complete code

// Create a statement and execute a select query

Statement s = conn.createStatement();

ResultSet r = s.executeQuery("select geom,id from geotable");

while (r.next()) {

// Retrieve the geometry as an object then cast it to the geometry type.

PGgeometry geom = (PGgeometry) r.getObject(1);

int id = r.getInt(2);

System.out.println("Row " + id + ":");

System.out.println(geom.toString());

} s.close(); conn.close();

JDBC sequence diagram

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Image source

PostGIS functions24

h2 and h2gis25

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Jaspa26

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http://jaspa.upv.es/blog/about-jaspa/

Readings27

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1.3.4

Readings28

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www.di.unipi.it/~confor/talks/SDBMS.ppt

• Spatial Databases and Spatial Data Management by Tatyana Budanskaya

Practical task29