Geographic Information Systems : Data Types, Sources and the ArcView Program

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Geographic Information Systems Data Types,
Sources and the ArcView Program
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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

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GIS Simplified (Review)

• A computer-based tool for mapping and analyzing
  things.

• Geospatial Database a set of compatible data
  layers or themes

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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
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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

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GIS Data Types
Discrete Space Vector Data -- Shapefiles
Continuous Space Raster Data -- Grids --
TINs (Triangulated Irregular
Networks) -- Images
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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
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Sample Point Shapfile Water Right Locations
A point shapefile
Each data point has a specific x,y coordinate pair
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Sample Line Shapefile River Reaches
Each line consists of two nodes and a series of
vertices
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Sample Polygon Shapefile River Basins
A closed set of lines illustrating the watershed
or drainage area for a corresponding river reach
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Types Combined
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Spatial Data Grid (Raster) format
Raster data are described by a cell grid, one
value per cell
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NEXRAD Rainfall Intensity Image October 18, 1994
_at_ 300 AM (CST)
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NEXRAD Rainfall Intensity Image October 18, 1994
_at_ 400 AM (CST)
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DEM Close Up
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Raster Vector Model
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Raster and Vector Data
Vector
Raster
Point
Line
Zone of cells
Polygon
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Points as Cells
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Line as a Sequence of Cells
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Polygon as a Zone of Cells
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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
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Image Data and Raster Overlays

• Samples attributes at fixed intervals
• List of numbers, one number per cell

Reservoir and Highway
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Triangulated Irregular Network (TIN)
Outside Channel Raster DEM
Inside Channel Vector cross-sections
Triangular mesh of (x,y,z) points
Triangles as elements
Result TIN of channel and landscape
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Three-Dimensional View of a TIN (Clear Creek and
Cowarts Creek Confluence)
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Hydrologic Cycle
Atmospheric water
Surface water
Subsurface water
Connecting processes in the hydrologic cycle
involves linking spatial features of various kinds
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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

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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

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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).

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Attributes

• GIS stores more than just maps
• Relationship between map features and attributes
  within a GIS
• Dynamic interactive maps

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Database Management System

• Inside the DBMS, spatial data is stored as
  digital layers with their associated attributes

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Levels of Analysis Relational Database
Relational Linkages
Spatial Attributes
Water Right Locations
Descriptive Attributes
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Feature Attribute Table (Vectors)
Fields
Records
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Value Attribute Table (Grids)
Attributes of grid zones
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Linked Tables
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Query Builder - find all countries with pop gt
1 million people
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Tables Edit, Join and Link
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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)
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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

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What is ArcView?

• Desktop geographic information system (GIS) from
  ESRI
• Uses scripting language called Avenue
• Customize GUI
• April 20, 2002 ArcGIS released

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Geographic Features
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Feature Attributes
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Feature Attributes
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Feature Attributes
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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

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Soil Map of TNRCC Management Segment 841 Lower
West Fork Trinity River
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30 m DEM of Lower West Fork, Trinity River
Both regions and features can be represented
using elements