Download Examples of GIS websites

GIS Databases
Jin Jie, Adrienne MacKay, Laura Saslaw
INLS 623 Database Systems I
April 18, 2007
GIS/Databases
Presentation Outline
• Overview (Adrienne)
*
• Tools (Jimmy)
• Examples (Laura)
* http://www.gis.com/whatisgis/graphics/gislayers.gif
What is GIS?
Geographic Information System:
“GIS is a collection of computer hardware,
software, and geographic data for
capturing, managing, analyzing, and
displaying all forms of geographically
referenced information.” *
* www.gis.com
Features of GIS
• Modern GIS uses digitized material
• Any variable that can be located spatially can be
used
• Primary requirement is knowing location:
– longitude, latitude, elevation
– geocode systems (zipcode, highway mile markers)
• Layers of information can be generated
• Expansive number of maps and databases
available
Working with Spatial Data Sources
Data Sources
– physical maps and records
– existing digital data
– remotely sensed data
• photogrammetry (aerial photography)
• satellite imagery (GPS, LIDAR)
• ground surveying
Integration of sources and challenges
– different coordinate systems, appropriate transformations
– merging maps with varying degrees of accuracy, rubber-banding
– interpolation (for missing data)
(note: enormous amounts of GIS data is available online)
Elmasri R, Navathe SB. Fundamentals of Database Systems. Fourth Ed.
www.wikipedia.org
GIS Across Disciplines
• Help people find resources with interactive maps (city of San
Diego)
• Track weather fronts and hurricanes (Florida Power and Light)
• Establish baseline information about bottle-nosed dolphins in
Florida Bay (The South Florida Ecosystem Restoration Program).
• Study the effects of global warming by the melt of glaciers in the
Himalayas
• Estimate travel time and traffic (city of Baltimore)
• Provide access to information previously difficult to use or
inaccessible (Libraries and Museums)
• Use as powerful visualization tool for education (K-12,
universities)
• Plan for emergency response (SAIC, FEMA)
• Allocate law enforcement resources
• Provide financial users with purchasing habits and behavior of
their customers
http://www.gis.com/whatisgis/geographymatters.pdf
GIS Views
• Database
• Map
• Model
Maps
• Locations
• Nearby Features
• Quantities
• What’s Inside
• Densities
• Changes over time
* http://www.gis.com/whatisgis/dowithgis.html
GIS Databases
• AKA: geodatabases, spatial databases
“…is a database with extensions for storing,
querying, and manipulating geographic
information and spatial data.” *
“the objects in a spatial database are
representations of real-world entities with
associated attributes” **
* http://en.wikipedia.org/wiki/Geodatabase
** http://www.geog.ubc.ca/courses/klink/gis.notes/ncgia/u11.html#SEC11.1
Types of Data
1. Spatial
– Vector
– Raster
– Image
Examples:
transportation networks
political boundaries
climatic regions
elevation features
2. Attribute
–
–
–
–
–
Tabular
Hierarchical
Network
Relational
Object Oriented
Examples:
socio-economic data
economic data
marketing data
geographic names
http://bgis.sanbi.org/GIS-primer/page_09.htm
Raster Data
Spatial data represented by:
• grid of cells
• cell size defines resolution
• each cell has a unique reference
that is used to attribute data
Advantages
• simple data structure and
processing
Disadvantages
• requires a lot of storage space
• high resolution images can be
analyzed by eye
• compatible with remote sensing
data
* http://www.colorado.edu/geography/gcraft/notes/datacon/datacon_f.html
Vector Data
Spatial data represented by:
• points (non-adjacent features)
• lines (represent linear features,
solid, dashed, color, thickness)
• polygons to represent objects
(boundaries, location points, etc);
most commonly used, represent
areas (color or pattern coded)
Disadvantages
Advantages
• can be very high resolution
• structures are complex
• graphical output similar to
hand drawn map
• requires less storage space
* http://www.colorado.edu/geography/gcraft/notes/datacon/datacon_f.html
1
I
4
II
Smith
Estate A34
IV
2
Birch
III
A35
3
Cherry
Spatial Data
Node Table
Node ID Easting Northing
1 126.5
578.1
2 218.6
581.9
3 224.2
470.4
4 129.1
471.9
Arc Table
Arc ID From N To N L Poly
I
4
1
II
1
2
III
2
3 A35
IV
3
4
Polygon Table
Polygon ID
Arc List
A34
I, II, III, IV
A35
III, VI, VII, XI
Relational Representation
R Poly
A34
A34
A34
A34
Attribute Data
Node Feature Attribute Table
Node ID Control
Crosswalk
1 light
yes
2 stop
no
3 yield
no
4 none
yes
ADA?
yes
no
no
no
Arc Feature Attribute Table
Arc ID Length Condition Lanes Name
I
106 good
4
II
92 poor
4 Birch
III
111 fair
2
IV
95 fair
2 Cherry
Polygon Feature AttributeTable
Polygon ID Owner
Address
A34
J. Smith 500 Birch
A35
R. White 200 Main
http://www.utdallas.edu/~briggs/poec5319/struct.ppt
Spatial Data Indexing
Grid (spatial index)
Quadtree
Octree
UB-tree
R-tree – The most common one
R-tree
• R-trees: tree data structures( similar to B-trees), dedicated for
spatial access methods.
• For example: A common real-world usage for an R-tree might
be: "Find all museums within 2 miles of my current location".
http://en.wikipedia.org/wiki/R-tree
-Hierarchically nested
R-tree
- Minimum bounding
rectangles
- Each node has a
variable number of
entries.
- Node stores two pieces
of data 1)Node ID 2)
Bounding box of all
entries within this child
node.
http://en.wikipedia.org/wiki/R-tree
Operations with R-tree Indexing
• Insertion / Deletion: using the bounding boxes from the
nodes to ensure that "nearby" elements are placed in the same
leaf node.
• Searching : using the bounding boxes to decide whether or not
to search inside a child node. (many nodes may never be
touched)
http://en.wikipedia.org/wiki/R-tree
Databases with spatial capability
• MySQL - Mysql Spatial Extensions
• Oracle – Oracle Spatial
• Postgres - PostGIS
Mysql Spatial Extensions
• MySQL 4.1: introduces spatial functionality in MySQL
• Motivation: Database that only works on simple data types,
such as INTEGER or DECIMAL, will just not be good enough
for geographic information.
http://dev.mysql.com/tech-resources/articles/4.1/gis-with-mysql.html
OpenGIS® Simple Features
specifications for SQL
MySQL GIS Datatypes (abstract types in gray)
The Open Geospatial Consortium (OGC) publishes the OpenGIS® Simple Features
Specifications For SQL, to propose conceptual ways for extending an SQL RDBMS to support
spatial data.
http://dev.mysql.com/tech-resources/articles/4.1/gis-with-mysql.html
Geometry Value
Properties of an internal geometry value:
• Type (point, linestring, polygon etc.). Exampel:point(1,1),
• SRID (Spatial Reference Identifier) - identifies the geometry's
associated Spatial Reference System .
• Coordinates. Example. Linestring(1 1, 3 4)
• Interior, Boundary, and Exterior – Exterior: all space
not occupied by the geometry. Interior: the space
occupied by the geometry. Boundary is the interface
between the geometry's interior and exterior.
http://dev.mysql.com/doc/refman/5.0/en/opengis-geometry-model.html
Geometry Value
• MBR (Minimum Bounding Rectangle) – It is formed by the minimum and
maximum (X,Y) coordinates.
• Its dimension (–1, 0, 1, or 2)
– –1: an empty geometry.
– 0 : no length and no area.
– 1: non-zero length and zero area.
– 2: non-zero area.
• Simple / non-simple (LineString, MultiPoint, MultiLineString) - whether
there are two points are equal.
• Closed / not closed (LineString, MultiLineString) – whether it forms a ring.
• Empty / non-empty – whether it has at least one point.
Data Types
Data types holding single geometry values:
•
•
•
•
GEOMETRY (geometry values of any type)
POINT
LINESTRING
POLYGON
Data types hold collections of values:
•
•
•
•
MULTIPOINT
MULTILINESTRING
MULTIPOLYGON
GEOMETRYCOLLECTION( a collection of objects of any type )
http://dev.mysql.com/doc/refman/5.0/en/mysql-spatial-datatypes.html
Creating Spatial columns
• Currently, spatial columns are supported for
MyISAM, InnoDB, NDB, BDB, and ARCHIVE
tables.
• Create a table with a spatial column:
CREATE TABLE geom (g GEOMETRY);
• Add / drop a spatial column:
ALTER TABLE geom ADD pt POINT;
ALTER TABLE geom DROP pt;
http://dev.mysql.com/doc/refman/5.0/en/creating-spatial-columns.html
Populating Spatial Columns
• Values should be stored in internal geometry format, but you
can convert them to that format from either Well-Known Text
(WKT) or Well-Known Binary (WKB) format.
• INSERT INTO geom
VALUES (GeomFromText('POINT(1 1)'));
• INSERT INTO geom
VALUES (GeomFromText(LINESTRING(0 0,1 1,2 2) ));
http://dev.mysql.com/doc/refman/5.0/en/populating-spatial-columns.html
Fetching Spatial Data
• Fetching spatial data in internal format(useful for inter-table transferring)
CREATE TABLE geom2 (g GEOMETRY)
SELECT g
FROM geom;
• In WKT format - The AsText() function converts a geometry from internal
format into a WKT string(text).
SELECT AsText(g)
FROM geom;
• In WKB format: - The AsBinary() function converts a geometry from
internal format into a BLOB containing the WKB value.
SELECT AsBinary(g)
FROM geom;
http://dev.mysql.com/doc/refman/5.0/en/fetching-spatial-data.html
Functions
• Conversion: AsBinary(g) , AsText(g), GeomFromText(wkt[,srid]) ,
GeomFromWKB(wkb[,srid])
• Geometry: Dimension(g), Envelope(g) , GeometryType(g), SRID(g) etc.
• Point: X(p), Y(p)
• LineString: EndPoint(ls), GLength(ls), NumPoints(ls) etc.
• MultiLineString: GLength(mls), IsClosed(mls)
• Polygon / MultiPolygon: Area() etc.
• GeometryCollection: NumGeometries(gc)
• More…….
http://dev.mysql.com/doc/refman/5.0/en/functions.html
Creating / Dropping Spatial Index
• Similar to build regular index, but extended with the
SPATIAL keyword.
CREATE TABLE geom (g GEOMETRY NOT NULL, SPATIAL INDEX(g));
ALTER TABLE geom ADD SPATIAL INDEX(g);
CREATE SPATIAL INDEX sp_index ON geom (g);
• Drop Index:
ALTER TABLE geom DROP INDEX g;
DROP INDEX sp_index ON geom;
http://dev.mysql.com/doc/refman/5.0/en/creating-spatial-indexes.html
Applications
• ESRI: ArcInfo
- It has a dominant share of the GIS software market with its
software used by 77% of GIS professionals
• Other vendors:
- MapInfo
- Intergraph
Shape Files
• Developed by ESRI
• It is a digital vector storage format for storing geometric location
and associated attribute information.
• They can be stored locally or accessed from remote sites(ie.
Davis Library GIS)
Mandatory files :
• .shp - the file that stores the feature geometry
• .shx - the file that stores the index of the feature geometry
• .dbf - the database of attributes
Optional Files: sbn, .sbx etc.
Connect ArcInfo to Database Server
See ArcInfo Example
GIS Standards
Standards have been developed by industry,
government, and the ISO for managing
geometric objects in RDMSs:
•
•
•
•
•
Storage options
Metadata
Table layer schema
Geometry types
SQL spatial data types
GIS database
standards
• ESRI Developer Network
http://edndoc.esri.com/arcsde/9.1/general_topics
/storing_geo_in_rdbms.html
• GIS open standards:
http://www.opengeospatial.org/ogc
• compliant products:
http://www.opengeospatial.org/resource/product
s/compliant
There are 2 types of file formats we most often see on
websites: raster and vector
The most common GIS raster data are
satellite images:
(my house!)
And vector images look like this:
Vector
Vector graphics…is
the use of geometrical
primitives such as
points, lines, curves,
and polygons, which are
all based upon
mathematical equations
to represent images in
computer graphics.
(http://en.wikipedia.org/wiki/Vec
tor_graphics)
http://ngmdb.usgs.gov/ngmdb/ngm_SMsearch.html
Floods in Argentina
Raster
Raster graphics is the
representation of images as a
collection of pixels (dots).
(http://en.wikipedia.org/wiki/Vector_graphics)
http://earthobservatory.nasa.gov/Newsroom/NewImages/imag
es_index.php3
Raster and vector are often seen together
• The state
boundaries are
______?______
• The colorful stuff
is _____?______
http://www.weather.gov/forecasts/graphical/sectors/
More examples of raster overlaid with vector
• http://www.biodiversity.bz/mapping/map_explore
r/dev_index.phtml
Vector over raster
http://www.zillow.com
Entered my address: 300 Reade Road, 27516
Examples Across Disciplines
• Help people find resources with interactive maps
http://mapmyrun.com/
• Track weather fronts and hurricanes
http://www.wunderground.com/global/Region/g4/2xIRSatellite.html
• Establish baseline information and track marine life.
http://www.esri.com/industries/marine/index.html
• Estimate travel time and traffic
http://www.traffic.com/Raleigh-Durham-Traffic/Raleigh-DurhamTraffic-Reports.html?ct=ma_map
http://www.gis.com/whatisgis/geographymatters.pdf
Trends
• GPS (vehicle navigation systems) have
become inexpensive and accurate
• Mass scale agriculture is using GIS, called
Precision Farming, to yield larger crops
and more profits
• US and other ports are using GPS to find
cargo containers on the lots for security
• Telemitry – http://www.traffic.com
GIS Advantages & Disadvantages
Advantages:
• Data availability
• Make better decisions
• Spans many disciplines
• Project planning
• Visual analysis
• Organizational Integration
Disadvantages:
• Complex system
• Data collection can be time-consuming
• Needs specialized equipment
• Privacy issues
Resources
Information
GIS at UNC (gis.unc.edu)
ESRI’s Guide to GIS (www.gis.com)
GIS on wikipedia (http://en.wikipedia.org/wiki/Gis)
Software
ESRI (available to UNC students for free)
http://www.esri.com/
Open Source GIS packages:
• GRASS GIS
• Quantum GIS