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Intro to advanced GIS and a review of basic GIS
Topic 1
Outlines
About the class setting Materials to be covered and scheduled Quick review of GIS basics First lab (Lab 1)
Materials to be covered and scheduled
A review of basic GIS (1) Spatial data analysis
Vector data analysis (2,3,4) Raster data analysis (5,6)
Spatial interpolation (7,8) 3-D analysis (12) Geoprocessing (9,10,11) Other topics (13)
We do not use one single book, because there is no single book covering all the materials I will cover in the class.
1. I will assign many ESRI-ebook for you to read
2. Many papers for you to read.
3. I will give quiz occasionally to see if you read them or not.
4. Other policies refer to the syllabus
What is GIS ?What is GIS ?
• A computer system for
- collecting,
- storing,
- manipulating,
- analyzing,
- displaying, and
- querying geographically related information.
In general GIS cover 3 components
Computer system Hardware
Computer, plotter, printer, digitizer Software and appropriate
procedures Spatially referenced or
geographic data People to carry out various
management and analysis tasks
Geographic Data
Geospatial data tells you where it is and attribute data tells you what it is. Metadata describes both geospatial and attribute data.
In GIS, we call geographic data as GIS data or spatial data
1. Geospatial data
Traditional method
To represent the geographic data is paper-based maps
Geology map Topographic map City street map (we still use it a lot) ...
Characteristics of spatial data
“mappable” characteristics: Location (coordinate system, will be lectured
later) Size is calculated by the amount (length, area,
perimeter) of the data Shape is defined as shape (point, line, area) of
the feature Discrete or continuous Spatial relationships
Discrete and continuous
Discrete data are distinct features that have definite boundaries and identities A district, houses, towns, agricultural
fields, rivers, highways, … Continuous data has no define
borders or distinctive values, instead, a transition from one value to another Temperature, precipitation, elevation, ...
GIS: a simplified view of the real world
Points Lines Areas Networks
A series of interconnecting lines
Road network River network Sewage network
Surfaces Elevation surface Temperature surface
Discrete features
Continuous features
Problems caused by the simplified features may still exist, but let’s live on it
Dynamic nature (not static) Forest grow River channel change City expand or decline
Identification of discrete and continuous features Road to be a line or a area?
Scale Some may not fit to any type of features: fuzzy
boundaries Transition area between woodland and grassland
Lets do not worry about these problems now!!! Just keep in mind
Points
A point is a 0 dimensional object and has only the property of location (x,y)
Points can be used to Model features such as a well, building, power, pole, sample location ect.
Other name for a point are vertex, node Point
Lines A line is a one-dimensional object that has
the property of length Lines can be used to represent road,
streams, faults, dikes, maker beds, boundary, contacts etc.
Lines are also called an edge, link, chain, arc
In an ArcInfo coverage an arc starts with a node, has zero or more vertices, and ends with a node
Line
Areas (Polygons)
A polygon is a two-dimensional object with properties of area and perimeter
A polygon can represent a city, geologic formation, dike, lake, river, ect.
Other name for polygons face, zoneArea
Topology needed
A collection of numeric data which clearly describes adjacency, containment (coincidence), and connectivity between map features and which can be stored and manipulated by a computer.
A set of rules on how objects relate to each other
Major difference in file formats
Higher level objects have special topology rules
Topology
© Paul Bolstad, GIS Fundamentals
Two basic data models to represent these features
Raster spatial data model Define space as an array of equally sized cells arranged in rows and
columns. Each cell contains an attribute value and location coordinates
Individual cells as building blocks for creating images of point, line, area, network and surface
Continuous raster Numeric values range smoothly from one location to another, for
example, DEM, temperature, remote sensing images, etc. Discrete raster
Relative few possible values to repeat themselves in adjacent cells, for example, land use, soil types, etc.
Vector spatial data model Use x-, y- coordinates to represent point, line, area, network,
surface Point as a single coordinate pair, line and polygon as ordered lists of
vertices, while attributes are associated with each features Usually are discrete features
DIGITAL SPATIAL DATA
• RASTER
• VECTOR
• Real World
Source: Defense Mapping School National Imagery and Mapping Agency
Raster and Vector Data Models
Vector RepresentationX-AXIS
500
400
300
200
100
600500400300200100
Y-AXIS
River
House
600
Trees
Trees
BB
B BB
BBB G
GBK
BBB
G
G
G GG
Raster Representation
1 2 3 4 5 6 7 8 9 1012345
67
8910
Real World
G G
Source: Defense Mapping School National Imagery and Mapping Agency
Example: Discrete raster
Xie et al. 2005
Example: continuous raster
Raster Real world Vector Heywood et al. 2006
Effects of changing resolutionHeywood et al. 2006
Vector – Advantages and Disadvantages
Advantages Good representation of reality Compact data structure Topology can be described in a network Accurate graphics
Disadvantages Complex data structures Simulation may be difficult Some spatial analysis is difficult or impossible
to perform
Raster – Advantages and Disadvantages
Advantages Simple data structure Easy overlay Various kinds of spatial analysis Uniform size and shape Cheaper technology
Disadvantages Large amount of data Less “pretty” Projection transformation is difficult Different scales between layers can be a nightmare May lose information due to generalization
GIS data formats (file formats)
Shapefiles Coverages TIN (e.g. elevation can be stored as TIN)
Triangulated Irregular Network
Grid (e.g. elevation can be stored as Grid) Image (e.g. elevation can be stored as
image, all remote sensing images)
Vector data
Raster data
Shape Files
Nontopological Advantages no overhead to
process topology Disadvantages polygons are
double digitized, no topologic data checking
At least 3 files .shp .shx .dbf
Coverages
Original ArcInfo Format Directory With Several Files Database Files are stored in the Info
Directory Uses Arc Node Topology
Containment (coincident) Connectivity Adjacency
TIN A triangulated irregular network (TIN) is a data model
that is used to represent three dimensional objects. In this case, x,y, and z values represent points. Using methods of computational geometry, the points are connected into what is called a triangulation, forming a network of triangles. The lines of the triangles are called edges, and the interior area is called a face, or facet.
While the TIN model is somewhat more complex than the simple point, line, and polygon vector model, or the raster model, it is actually quite useful for representing elevations. For example a raster grid would require grid cells to cover the entire surface of a geographic area. Also, if we wanted to show great detail we would have to have small grid cells. Now, if the land area is relatively flat, we would still need the small grid cells. However, with a TIN we would not have to include so many points on the flat areas, but could add more points on the steep areas where we want to show greater detail.
The illustration shows how we can create a TIN of the terrain around Ithaca, NY.
First, a series of elevation points are created Second, a TIN face is created with the elevation data Third, the faces are shaded in to give the impression of a 3D
surface
©Arthur J. LemboCornell University
Components of a TIN Nodes Edges Triangles Hull Topology
©Arthur J. LemboCornell University
Grid Properties
Each Grid Cell holds one value even if it is empty.
A cell can hold an index standing for an attribute.
Cell resolution is given as its size on the ground.
Point and Lines move to the center of the cell.
Minimum line width is one cell.
Rasters are easy to read and write, and easy to draw on the screen.
A new data model in ArcGIS
Geodatabase data model Use a relational database that stores geographic data
A type of database in which the data is organized across several tables. Tables are associated with each other through common fields. Data items can be recombined from different files.
A container for storing spatial and attribute data and the relationships that exist among them
And their associated attributes can be structured to work together as an integrated system using rules, relationships, and topological associations
Geodatabase components-vector data and table
Primary (basic) components - feature classes, - feature datasets,- nonspatial tables.
complex components building on the basic components:
- topology, - relationship classes, - geometric networks
Geodatabase components-Raster data
Raster data referenced only in personal geodatabase Raster data physically stored in multiuser geodatabse Raster datasets and raster catalogs
A raster dataset is created from one or more individual rasters. When creating a raster dataset from multiple rasters, the data is mosaicked, or aggregated, into a single, seamless dataset in which areas of overlap have been removed. The input rasters must be contiguous (adjacent) and have the same properties, including the same coordinate system, cell size, and data format. For each raster dataset (.img, grid, JPEG, MrSID, TIFF), ArcGIS creates an ERDAS IMAGINE file (.img).
A raster catalog is defined as a table in the geodatabase which you can view like any other table in ArcCatalog. Each raster in the catalog is represented by a row in the table. It contains a collection of rasters that can be noncontiguous, stored in different formats, and have other different properties. In order to view all the rasters in the catalog, they must have the same coordinate system and a common geographic extent
2. Attribute data Attribute data is about “what” of a
spatial data and is a list or table of data arranged as rows and columns Rows are records (map features)
Each row represents a map feature, which has a unique label ID or object ID
Columns are fields (characteristics) Intersection of a column and a row shows
the values of attributes, such as color, ownership, magnitude, classification,…
examples
A database needed
If many fields related to one record (feature-ID), for example, the a soil unit can have over 80 estimated physical and chemical properties, more tables are needed to store all the attributes.
A database management system (DBMS) is needed to manage multiple tables.
A database is a collection of interrelated tables in digital format. There are four types: Flat file, hierarchical database, network database,
relational database In GIS, we usually use relational database
Flat file Hierarchical
NetworkRelational
PIN: Parcel ID number
Zoning (zonecode): 1-residential, 2-commercial Chang, 2004
Relational database
A relational database is a collection of tables, also called relations, which can be connected to each other by keys.
A primary key represents one or more attributes whose values can uniquely identify a record in a table. Its counterpart in another table for the purpose of linkage is called a foreign key
Advantages Each table in the database can be prepared, maintained,
and edited separately from other tables Efficient data management and processing, since linking
tables query and/or analysis is often temporary
Four tables linked by keys
Chang, 2004
Relationship of those separate tables
One record in one table related to one record in another table
One record in one table related to many records in another table
Many records in one table related to one record in another table
Many records in one table related to many records in another table
Join and relate tables
Join
Join
relate
relate
Once tables are separated as relational tables, then two operations can be used to link those tables during query and analysis
Join, brings together two tables based on a common key.
Relate, connects two tables (based on keys) but keeps the tables separate.
Keys do not have to have the same name but must be of the same data type
One-to-One Join
Employee-id Job
1 Digislave
2 Useless Supervisor
Employee-id name
1 Tom
2 John
After join
Employee-id Job Name
1 Digislave Tom
2 Useless Supervisor John
Join Employee-id to Employee-id
Many-to-One JoinSymbol Description
Qa Quaternary Alluvium
Qe Quaternary Eolian
Pa Permian Abo
Polygon Id Symbol
1 Qa
2 Qa
3 Pa
4 Qe
Polygon ID Symbol Description
1 Qa Quaternary Alluvium
2 Qa Quaternary Alluvium
3 Pa Permian Abo
4 Qe Quaternary Eolian
After Join on Symbol
One-to-Many Relates
Formation Symbol
Quaternary Alluvium
Qa
Permian Abo Pa
Symbol Mineral
Qa Quartz
Pa Quartz
Qa Gypsum
Pa Feldspar
If the tables are related on Symbol, selecting Polygon-id 1 will select the highlighted areas.
Many-to-Many Relates
Formation Symbol
1 Qa
2 Qa
Symbol Mineral
Qa Quartz
Pa Quartz
Qa Gypsum
Pa Feldspar
If the tables are related on Symbol, selecting Polygon-id 1 will select the highlighted areas.
Tables In ArcGIS GIS
Those separate tables will have one and only one table called spatial table (or layer attribute table), which has spatial location and relationship with the spatial data. Other tables called nonspatial tables, which can be either join or relate to the spatial table.
Join tables when each record in the spatial table has no more than one matching record in the nonspatial table One to one relation Many to one relation
Relate tables when each record in the spatial table has more than one record in the nonspatial table One to many relation Many to many relation
The joined table
The joined table will only preserved within the map document-the tables remain separate on disk-and can be removed at any time
Related tables
The related table will only preserved within the map document-the tables remain separate on disk-and can be removed at any time
3. metadata
Meta is defined as a change or transformation. Data is described as the factual information used as a basis for reasoning. Put these two definitions together and metadata would literally mean "factual information used as a basis for reasoning which describes a change or transformation."
In GIS, Metadata is data about the data. It consists of information that describes spatial data and is used to provide documentation for data products. Metadata is the who, what, when, where, why, and how about every facet of the spatial data.
According to the Federal Geographic Data Committee (FGDC), metadata is data about the content, quality, condition, and other characteristics of data.
Why use and create Why use and create metadatametadata
To help organize and maintain an organization's spatial data
- Employees may come and go but metadata can catalogue the changes and updates made to each spatial data set and how each employee implemented them
To provide information to other organizations and clearinghouses to facilitate data sharing and transfer
- It makes sense to share existing data sets rather than producing new ones if they are already available
To document the history of a spatial data set - Metadata documents what changes have been
made to each data set, such as changes in geographic projection, adding or deleting attributes, editing line intersections, or changing file formats. All of these could have an effect on data quality.
Metadata Should Include Data about
Date of data collected. Date of coverage generated. Bounding coordinates. Processing steps.
Software used RMSE, etc.
From where original data came. Who did processing. Projection coordinate System Datum Units Spatial scale Attribute definitions Who to contact for more information
See an example of non-standard metadata (see)
Federal Geographic Data Committee’s (FGDC) Content Standard for Digital Geospatial Metadata (CSDGM)
The FGDC is developing the National Spatial Data Infrastructure (NSDI) in cooperation with organizations from State, local and tribal governments, the academic community, and the private sector. The NSDI encompasses policies, standards, and procedures for organizations to cooperatively produce andshare geographic data.
The objectives of the CSDGM are to provide a common set of terminology and definitions for the documentation of digital geospatial data.
CSDGM (FGDC-STD-001-
1998)
Metadata = Identification_Information Data_Quality_Information Spatial_Data_Organization_Information Spatial_Reference_Information Entity_and_Attribute_Information Distribution_Information Metadata_Reference_Information
Connect to http://www.fgdc.gov/metadata/csdgm/
Metadata toolsMetadata tools Metadata editors:
- tkme / USGS- ArcCatalog / ESRI- SMMS / Intergraph- FGDCMETA / Illinois State Geological Survey- xtme / USGS
Metadata utilities (check compliance and export to text, HTML,XML, or SGML):
- mp / USGS- MP batch / Intergraph- ArcCatalog powered by mp/ ESRI
Metadata Server- Isite / FGDC- GeoConnect Geodata Management Server / Intergraph- ArcIMS Metadata Server / ESRI
mp: Metadata Parser
FGDC Clearinghouse the FGDC developed a clearinghouse
that allows geospatial data creators to share their data
however, the FGDC Clearinghouse is not a data repository. The data contained within the clearinghouse is actually stored on computer servers maintained by individual contributors. This allows contributors to manage their own data.
Two Components The FGDC Clearinghouse consists
of 6 gateways and 250 nodes A gateway is a point of entry into
the FGDC Clearinghouse A clearinghouse node is a
database that contains metadata records. Individual contributors maintain nodes
Besides the FGDC Clearinghouse, there are a variety of other communities that use FGDC-compliant metadata as the basis of their data sharing services. These so-called clearinghouse communities are often developed because the participating organizations have data of similar or complementary types.
http://clearinghouse1.fgdc.gov/
4. Geodatabase
Before geodatabase, in one GIS project, many GIS files (spatial data and nonspatial data) are stored separated. So for a large GIS project, the GIS files could be hundreds.
Within a geodatabase, all GIS files (spatial data and nonspatial data) in a project can be stored in one geodatabase, using the relational database management system (RDMS)
Types of geodatabases
personal enterprise
Personal Geodatabase
The personal geodatabase is given a name of filename.mdb that is browsable and editable by the ArcGIS, and it can also be opened with Microsoft Access. It can be read by multiple people at the same time, but edited by only one person at a time. maximum size is 2 GB.
Multiuser Geodatabase
Multiuser (ArcSDE or enterprise) geodatabase are stored in IBM DB2, Informix, Oracle, or Microsoft SQL Server.
It can be edited through ArcSDE by many users at the same time, is suitable for large workgroups and enterprise GIS implementations. no limit of size. support raster data.
3-tier ArcSDE client/server architecture with both the ArcSDE and Oracle RDBMS running on the same server, which minimizes network traffic and client load while increasing the server loadcompared to 2-tier system, in which the clientsdirectly connect to the RDBMS
Personal and Multiuser Geodatabase Comparison
source: www.esri.com
5. Lab 1
Getting Started With the Geodatabase
About 2 hours
About 1 hour
COPY the result map of your last step to your home work
Copy your exam questions and result to your homework