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)

ArcViewDigital

ElevationModel

HEC-HMSFlow

discharge

HEC-RASWatersurfaceprofiles

ArcViewFlood

plain maps

HEC-GeoHMS HEC-GeoRAS

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

PointPoint - a pair of x and y coordinates(x1,y1)

LineLine - a sequence of points

PolygonPolygon - a closed set of lines

Node

vertex

Vector data are defined spatially as either:

Sample Point Shapfile: Water Right Locations

Each data point has a specific x,y coordinate pair

A “point” shapefile

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 areafor a corresponding river reach

Types Combined

Spatial Data: Grid (Raster) format

Numberof

rows

Number of Columns(X,Y)

Cell size

NODATA cell

Raster data are described by a cell grid, one value per cell:

NEXRAD Rainfall Intensity ImageOctober 18, 1994 @ 3:00 AM (CST)

NEXRAD Rainfall Intensity ImageOctober 18, 1994 @ 4:00 AM (CST)

DEM Close Up

Raster – Vector Model

Raster and Vector Data

PointPoint

LineLine

PolygonPolygon

VectorVector RasterRaster

Zone of cells

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

Outside Channel: Raster DEM

Result: TIN of channel and landscape

Triangular mesh of (x,y,z) points

Triangles as elements

Three-Dimensional View of a TIN(Clear Creek and Cowarts Creek Confluence)

Hydrologic Cycle

Atmosphericwater

Surfacewater

Subsurfacewater

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 LinkagesSpatial Attributes

Descriptive Attributes

Water RightLocations

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)

Primary Key field (each record must

have a unique value)Relate field

(can have one or manyrecords for each value)

Many to onerelation

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