Module 19

Working with SQL Server® 2008 R2

Spatial Data

Module Overview

• Introduction to Spatial Data

• Working with SQL Server Spatial Data Types

• Using Spatial Data in Applications

Lesson 1: Introduction to Spatial Data

• Target Applications

• Types of Spatial Data

• Planar vs. Geodetic

• OGC Object Hierarchy

• Spatial Reference Identifiers

• Demonstration 1A: Spatial Reference Systems

Target Applications

• There is a perception that spatial applications are quite separate to mainstream business applications

• Almost every business application can benefit from spatial data and functions Locations of customers, stores, offices

All addresses

Intersections and distances

• Business Intelligence applications particularly benefit from spatial visualizations

Types of Spatial Data

• Vector vs. Raster Data Vector – series of line segments Raster – pixels or dots

• 2D, 3D, 4D

Planar vs. Geodetic

• Planar systems = Flat Earth

• Geodetic systems (e.g. GPS) = Round Earth

OGC Object Hierarchy

• Open Geospatial Consortium is the relevant industry body OGC defined an object tree

• SQL Server data types are based on the Geometry hierarchy

Spatial Reference Identifiers

• Each spatial instance has a spatial reference identifier (SRID)

• SRID corresponds to a spatial reference system that is a way of performing measurements

• SRID 4326 is the WGS84 system (commonly implemented as the GPS system)

• SRID 0 is used when no system is needed (flat earth)

• When two spatial instances are used in a calculation, their SRIDs must match

• EPSG standard is used to define available SRIDs

Demonstration 1A: Spatial Reference Systems

In this demonstration, you will see:

• The available Spatial Reference Identifiers

• The available units of measurement

Lesson 2: Working with SQL Server Spatial Data Types

• SQL Server Spatial Data

• System vs. User SQL CLR Types

• geometry Data Type

• geography Data Type

• Spatial Data Formats

• OGC Methods and Properties

• Microsoft Extensions

• Demonstration 2A: Spatial Data Types

SQL Server Spatial Data

• Data Types geometry data type (flat Earth - planar)

geography data type (round Earth - geodetic)

• Bing Maps SDK updated

• SQL Server Reporting Services map control

• Microsoft.SqlServer.Types assembly

• OGC and Microsoft extension methods ST prefix on OGC defined methods

No prefix on Microsoft extension methods

System vs. User SQL CLR Types

• System types are enabled regardless of ‘clr enabled’ setting

• geometry, geography, hierarchyid use large CLR object support

• Call properties and methods on CLR objects via:

Calling Method Example

Instance.Property NewYork.STArea

Instance.Method() Border.MakeValid()

Type::StaticMethod() geometry::STGeomFromText()

SELECT name, assembly_id, permission_set_desc, is_user_defined FROM sys.assemblies;

SELECT name, assembly_id, permission_set_desc, is_user_defined FROM sys.assemblies;

geometry Data Type

DECLARE @Shape geometry;SET @Shape = geometry::STGeomFromText( 'POLYGON ((10 10, 10 30, 40 40, 20 10, 10 10))',0);SELECT @Shape;

DECLARE @Shape geometry;SET @Shape = geometry::STGeomFromText( 'POLYGON ((10 10, 10 30, 40 40, 20 10, 10 10))',0);SELECT @Shape;

• 2D data type

• STX and STY properties

• SRID is not relevant – defaults to zero

• Comprehensive OGC coverage

geography Data Type

SELECT Border FROM dbo.CountriesWHERE CountryName = 'Italy';SELECT Border FROM dbo.CountriesWHERE CountryName = 'Italy';

• 2D data type

• Long and Lat properties

• Order is important for polygons

• Single value cannot span more than a single hemisphere

Spatial Data Formats

• Internal binary format of the spatial types not normally used directly

• Need to be able to input/output as strings

• Parsing WKT – Well known text

WKB – Well known binary

GML – Geography markup language (XML variant)

Parse() assumes WKT

• Output Options to output above formats including Z and M values

ToString() provides WKT

OGC Methods and Properties

Common methods

Common Collection Properties

Method Description

STDistance The distance between two shapes

STIntersects The shape formed by the intersection of two shapes

STArea The area of a shape

STLength The length of a shape (for a polygon, the sum of the lengths of all sides)

STUnion The shape formed by uniting two shapes

STBuffer The shape formed by providing a buffer region around a shape

Properties Description

STPointN Returns a specific point in a collection of points

STGeometryN Returns a specific geometric shape from a collection of geometries

Microsoft Extensions

• Microsoft has provided a number of extensions to the OGC defined methods and properties

• Common extensions:

Method Description

MakeValid Returns a valid shape from a potentially invalid shape

Reduce Reduces the complexity of a shape without changing its basic shape

IsNull Returns if an object is NULL

AsGml Returns the object coded as GML (Geographic Markup Language)

BufferWithTolerance Returns a buffer around an object but uses a tolerance value to allow for rounding errors

Demonstration 2A: Spatial Data Types

In this demonstration, you will see how to work with SQL Server spatial data types

Lesson 3: Using Spatial Data in Applications

• Performance Issues in Spatial Queries

• Tessellation Process

• Spatial Indexes

• Implementing Spatial Indexes

• geometry Methods Supported by Spatial Indexes

• geography Methods Supported by Spatial Indexes

• Extending SQL Server Spatial

• Demonstration 3A: Spatial Data in Applications

Performance Issues in Spatial Queries

• Spatial queries can involve a large number of data points

• Imagine trying to locate streets that intersect your suburb or region

• Executing methods like STIntersects for a large number of points is slow

• How could you simplify the problem?

• Spatial indexes are designed to help avoid these unnecessary calculations

Tessellation Process

• Spatial indexes allow us to break large problems into ever smaller problems as we move through relevant levels

• SQL Server uses a four-level grid

• Tessellation rules are applied to eliminate areas not touched by the shape

Spatial Indexes

• Spatial indexes in SQL Server work in a two-phase method

• Primary filter Finds all possible candidates

False positives are ok at this stage

No false negatives

• Secondary filter Removes false positives

Applies the spatial method (that is, STIntersects) from the original predicate in your WHERE clause

• Filter method shows effectiveness of the Primary filter

Implementing Spatial Indexes

CREATE SPATIAL INDEX IX_ObjectOutline_ShapeON dbo.ObjectOutline (Shape)WITH (BOUNDING_BOX=(0,0,512,512), GRIDS =(LOW,LOW,LOW,LOW));

CREATE SPATIAL INDEX IX_ObjectOutline_ShapeON dbo.ObjectOutline (Shape)WITH (BOUNDING_BOX=(0,0,512,512), GRIDS =(LOW,LOW,LOW,LOW));

• Use the CREATE SPATIAL INDEX statement geometry has a BOUNDING_BOX ONLINE builds are not supported

• Can be useful to index one column more than once with different tessellation levels

• Table must have a clustered primary key

geometry Methods Supported by Spatial Indexes

• Not all methods benefit from spatial indexes

• Not all predicate forms benefit from spatial indexes

• Supported forms:

geometry1.STContains(geometry2) = 1

geometry1.STDistance(geometry2) < number

geometry1.STDistance(geometry2) <= number

geometry1.STEquals(geometry2)= 1

geometry1.STIntersects(geometry2)= 1

geometry1.STOverlaps(geometry2) = 1

geometry1.STTouches(geometry2) = 1

geometry1.STWithin(geometry2)= 1

geography Methods Supported by Spatial Indexes

• Not all methods benefit from spatial indexes

• Not all predicate forms benefit from spatial indexes

• Supported forms:

geography1.STIntersects(geography2)= 1

geography1.STEquals(geography2)= 1

geography1.STDistance(geography2) < number

geography1.STDistance(geography2) <= number

Extending SQL Server Spatial

• Functions from CodePlex IsValidGeographyFromGeometry, IsValidGeographyFromText,

MakeValidGeographyFromGeography, MakeValidGeographyFromText, ConvexHullGeography, ConvexHullGeographyFromText, DensifyGeography, InterpolateBetweenGeog, InterpolateBetwenGeom, LocateAlongGeog, LocateAlongGeom, ShiftGeometry, VacuousGeographyToGeometry, VacuousGeometryToGeography

• Types from CodePlex SqlProjection (Abers Equal Area, Equirectangular, Lambert

Conformal Conic, Mercator, Oblique Mercator, Transverse Mercator, Gnomonic)

AffineTransform

• Aggregates from CodePlex GeographyUnionAggregate, GeometryEnvelopeAggregate

Demonstration 3A: Spatial Data in Applications

In this demonstration you will see how to use SQL Server spatial data to solve some business questions

Lab 19: Working with SQL Server Spatial Data

• Exercise 1: Familiarity With Geometry Data Type

• Exercise 2: Adding Spatial Data to an Existing Table

• Challenge Exercise 3: Business Application of Spatial Data (Only if time permits)

Logon information

Estimated time: 45 minutes

Virtual machine 623XB-MIA-SQL

User name AdventureWorks\Administrator

Password Pa$$w0rd

Lab Scenario

Your organization has only recently begun to acquire spatial data within its databases. The new Marketing database was initially designed prior to the company beginning to implement spatial data. One of the developers has provided a table of the locations where prospects live. It is called Marketing.ProspectLocation. A second developer has added columns to it for Latitude and Longitude and geocoded the addresses. You will make some changes to the system to help support the need for spatial data.

Lab Review

• Where would you imagine you might use spatial data in your own business applications?

Module Review and Takeaways

• Review Questions

• Best Practices