Transcript CEVE 512 – Lab 2

Geographic Information Systems :
Data Types, Sources and the ArcView Program
Overview
• Lecture (50 min)
– Review
– Spatial Data
• Shapefiles, Images, Grids, TINs
– Relational Databases
• Links and Joins
– What is ArcView
– Scale and Resolution
• Break (15 min)
• ArcView Intro Lab (75 minutes)
• Homework Assignment
GIS: Simplified (Review)
• A computer-based tool
for mapping and
analyzing things.
• Geospatial
Database: a set of
compatible data
layers or themes
Digital Hydrologic / Hydraulic
Processing (Review)
HEC-RAS
Water
surface
profiles
HEC-HMS
Flow
discharge
HEC-GeoHMS
HEC-GeoRAS
ArcView
Digital
Elevation
Model
ArcView
Flood
plain maps
Digital Map Database
GIS: Analysis (Review)
• Why should spatial data be stored in a GIS?
– Want to use the power of the computer to ask
queries of the spatial data
– Analyze data and produce new information
– Convey technical data non-technically
GIS Data Types
Discrete Space: Vector Data
-- Shapefiles
Continuous Space: Raster Data
-- Grids
-- TINs (Triangulated Irregular
Networks)
-- Images
Vector Data: Types
Vector data are defined spatially as either:
(x1,y1)
Point - a pair of x and y coordinates
vertex
Line - a sequence of points
Node
Polygon - a closed set of lines
Sample Point Shapfile: Water Right
Locations
A “point”
shapefile
Each data point has a specific x,y coordinate pair
Sample Line Shapefile: River Reaches
Each “line” consists of two nodes and a series of vertices
Sample Polygon Shapefile:
River Basins
A closed set of lines illustrating the watershed or drainage area
for a corresponding river reach
Types Combined
Spatial Data: Grid (Raster) format
Raster data are described by a cell grid, one value per cell:
Cell size
Number
of
rows
NODATA cell
(X,Y)
Number of Columns
NEXRAD Rainfall Intensity Image
October 18, 1994 @ 3:00 AM (CST)
NEXRAD Rainfall Intensity Image
October 18, 1994 @ 4:00 AM (CST)
DEM Close Up
Raster – Vector Model
Raster and Vector Data
Vector
Raster
Point
Line
Zone of cells
Polygon
Points as Cells
Line as a Sequence of Cells
Polygon as a Zone of Cells
Image Data and Vector Overlays
• Image data is nothing more than a properly placed picture. Actually
made of pixels of a certain cell size much like raster data.
– Smaller the cell size – the more refined the resolution – the sharper the
picture
• Vector representations are often traced from a “base” image map
Reservoir and Highway
Image Data and Raster Overlays
• Samples attributes at fixed intervals
– List of numbers, one number per cell
Reservoir and Highway
Triangulated Irregular Network (TIN)
Inside Channel:
Vector cross-sections
Triangles
as elements
Outside Channel:
Raster DEM
Triangular
mesh of
(x,y,z) points
Result: TIN of channel and landscape
Three-Dimensional View of a TIN
(Clear Creek and Cowarts Creek Confluence)
Hydrologic Cycle
Atmospheric
water
Surface
water
Subsurface
water
Connecting processes in the hydrologic cycle
involves linking spatial features of various kinds
Section Summary
• Four types of GIS data:
–
–
–
–
Shapefiles (point, line, polygon)
Grids
TINs
Images
• A real-world region can be considered spatially discrete or
spatially continuous
• Discrete space is represented by features in vector data
(shapefiles) and continuous space by elements or cells in
raster data (grids)
• Both vector and raster data are required to represent the
real-world in the digital GIS world  Raster-Vector
model
Overview
• Lecture (45 min)
– Review
– Spatial Data
• Shapefiles, Images, Grids, TINs
– Relational Databases
• Links and Joins
– What is ArcView
– Scale and Resolution
• Break (15 min)
• ArcView Intro Lab (75 minutes)
• Homework Assignment
GIS: Data Entry and Storage
• Store data in a logical way
• Maps and data are stored in digital form
• Digital layers with attributes attached
• Layers are stored together in a relational
database using a database management
system (DBMS).
Attributes
• GIS stores more than
just maps
• Relationship between
map features and
attributes within a GIS
• Dynamic interactive
maps
Database Management System
DBMS
• Inside the DBMS, spatial data is stored
as digital layers with their associated
attributes
Levels of Analysis:
Relational Database
Relational Linkages
Spatial Attributes
Water Right
Locations
Descriptive Attributes
Feature Attribute Table (Vectors)
Fields
Records
Value Attribute Table (Grids)
Attributes of grid zones
Linked Tables
Query Builder - find all countries with pop >
1 million people
Tables: Edit, Join and Link
Edit
Join
Link
Relationships in Linking and Joining Tables
Source Table
(new information
to be added)
Destination Table
(existing information)
Many to one
relation
Primary Key field
(each record must
have a unique value)
Relate field
(can have one or many
records for each value)
Concept Summary
• All GIS data files have descriptive attributes in a
data table associated with each file
• Feature attributes (associated with vector files)
form the basis for data analysis of these files
• Value attributes (associated with grid files) form
the basis for continuous representation of data
across a surface (precipitation, elevation, etc)
• Attribute tables can be linked or joined to related
tables using a key field
What is ArcView?
• Desktop geographic information system
(GIS) from ESRI
• Uses scripting language called Avenue
• Customize GUI
• April 20, 2002 – ArcGIS released
Geographic Features
Feature Attributes
Feature Attributes
Feature Attributes
Overview
• Lecture (45 min)
– Review
– Spatial Data
• Shapefiles, Images, Grids, TINs
– Relational Databases
• Links and Joins
– What is ArcView
– Scale and Resolution
• Break (15 min)
• ArcView Intro Lab (75 minutes)
• Homework Assignment
Soil Map of TNRCC Management Segment 841
Lower West Fork Trinity River
30 m DEM of Lower West Fork, Trinity River
Both regions and features can
be represented using elements