1960s:

- Canada Geographic Information System (CGIS)

- Harvard Lab for Computer Graphics and Spatial Analysis

- Environmental Systems Research Institute (ESRI)

1970s:

- Landsat Satellite; IBM's GFIS

- Odyssey GIS by the Harvard Lab ~ first modern vector GIS

1980s:

- Arc/Info by ESRI, MapInfo

- GPS became operational in 1985

1990s:

- ESRI ArcView ~ Merging of GIS and GPS

- GIS migration from workstation to PC

2000s:

- Internet

- Wireless

GIS Components:

- Hardware (input and output devices/equipment)

- Software

- People

Vector: line based, single points

Rastor: based on an area, shaded pixels

A database management tool

 A powerful analytical tool

 An effective communication tool

**Anything with a spatial component**

- Environmental Research

- Agriculture

- Military

- Emergency Planning/Public Health

- Natural Resource Management

- Business Development/Community Design

- Utility Management

- Anthropology/Archaeology

**Be thinking of examples**

**what makes it the foundation of GIS**

Datums

Projections

Coordinate Systems

Data

Visualization

Catal Hyuk ~ 6000 BC

Ga-Sur (Iraq) ~ 2500-3800 BC

An index of measuring how flat the ellipsoid is. And ellipsoid (a mathematical model) is used to approximate the size and shape of Earth.

f = (a-b)/a

f=1/298 (for Earth)

a=equatorial axis

b=polar axis

**a and b depend on the selection of datums**

A model of the surface of the earth based on a surveyed network of physical points.

Datum=Ellipsoid+Point of Origin

A datum approximates the shape of the earth.

A datum defines the position of the spheroid relative to the center of the earth. 

A datum provides a frame of reference for measuring locations on the surface of the earth. 

A datum defines the origin and orientation of latitude and longitude lines. 

- the reference ellipsoid

**Both the shape of the ellipsoid and the position relative to the Earth are important**

- a set of survey points

- Earth-centered Datums ex. WGS84

- Local Datums ex. NAD27

**two bwcause the surface of the earth is not smooth**

Most Common in US: 

NAD27 - North American Datum of 1927

NAD83 - North American Datum of 1983

World Datum:

WGS84 - World Geodetic System of 1984 (used for GPS)

Sets of mathematical equations that convert coordinates from one system to another.

Systematic transformations of spheroidal shape of the earth so that the curved, three-dimensional shape of a geographic area on the earth can be represented in two dimensions as x and y coordinates.

Ideally, a 3D globe with accurate shape is the best approximation of the Earth, but globes are difficult to make, carry, update and make measurements on.

Transforming from 3D to 2D will help solve these problems.  

Distortion-Based:

• Conformal Projections
• Equal Area Projections
• Equidistance Projections

Shape-Based:

• Conic Projections
• Cylindrical Projections
• Planar Projections 
• Azimuthal/Polar Projections

State Plane

UTM ~ Universal Transverse Mercator

- A ratio between distances on the map and corresponding distances in the real world.

- It's also an expression of how much the area represented has been reduced on the map.

- Map scale is important for understanding maps both in paper and computer form. 

Verbal Scale: expresses in words a relationship between a map distance and a ground distance (ex. one inch represents 16 miles)

Graphic/Bar Scale: The most common found on maps

Representative Fraction/Ratio Scale:

(ex. 1/24,000 or 1:24,000)

Vector: represent geographic phenomena with points, lines and polygon points

Raster: matrix of cells

Components:

Points

Lines

Polygons

Characteristics:

- "ArcNode" Topology: Arcs are composed of nodes and vertices, and arcs begin and end at nodes with vertices in between

- Depends on Scale: a building can be represented by a point or a polygon depending on the scale of the landscape

- Useful for representing and storing discrete features such as buildings, pipes or parcel boundaries

- Has an attribute table associated with feature

Components:

Matrix(grid) of cells, each with a width and height and is a portion of the entire area represented

Characteristics: 

- Cell size determines resolution: smaller cell size=more accurate but takes up a lot more storage space

- Only one corner of the raster layer is georeferenced

- Location of each cell is defined by its row or column location within the matrix

- Represented by Cartesian Coordiante System with rows parallel to the x-axis, columns parallel to y-axis

- Each cell has ONE value, which represents the property or attribute of interest

- Values can be positive, negative, integer, floating-point, or even nodata

- Gradation: (Lefthand column in ArcGIS) High Level to Low Level

Advantages: 

- Good representation of reality

- compact data structure ie doesn't take up as much room

- Topology can be described in a network

- Accurate graphics

Disadvantages: 

- Complex data structure ie requires very accurate data

- Simulation can be difficult

- Some spatial analysis is difficult or impossible to perform

Advantages: 

- Simple data structure (ONE value)

- Easy overlay with complex data

- Good for various kinds of spatial or statistical analyses

- Ability to uniformly store points, lines, polygons and surfaces

Disadvantages: 

- Inherent spatial inaccuracies due to cell-based feature representation (approximation)

- Large amount of data, takes up a lot of storage space

- Different scales between layers can be a nightmare

- Information loss due to generalization

Triangulated Irregular Network:

- Data model that is used to represent 3D objects

- Network of linked triangles drawn between irregularly spaced points with x, y and z values

- Each triangle assumes a constant gradient. The slope and aspect for the x, y and z values at the three points that make up the triangle.

- More complex than vector or raster data.

- Efficient way to store and analyze surface. 

- Should not be used for mountainous terrain, but rather flatlands because of constant gradient.

ArcInfo Coverage 

ArcView Shapefile

Geodatabase

CAD

ArcInfo GRID

DEM: Digital Elevation Model

DOQ: Digital Othophoto Quadrangles

Satellite Images

Aerial Photos

Scanned Maps

Graphical Images (TIFF, JPEG, BMP)

- Latest format and preferred in ArcGIS

- Relational databases that contain geographic information ie geographically referenced

- Contain feature classes and tables

- Store many different vector and rastor layers as well as tables, layer files, topographical relationship, models and more in a single database file

- all feature classes in a feature dataset share the same coordinate system

- can be easily shared among users, so much less code can be emailed

Personal 

Multiuser

Digital Elevation Model

- Most important

- Consists of an array of uniformly spaced elevation data

- Mostly developed by USGS, free data for US, Canada and Puerto Rico

- Non-USGS DEM is LIDAR: different type, based on different projection

- Global DEMs: GTOPO30, small cell size, NOT free

.shp

.shx

.dbf

Nominal: categories, can be text or number; computing is nonsense

Ordinal: rank, classification

Interval: no absolute scale, ex. temperature

Ratio: absolute value, continuous, one set porportion of other set

Cyclical: used to characterize directional attributes

Government Agencies: Federal, State and Local

Commercial Data Venders

The Internet

Research Community 

Yourself

- Data about data.

- Information about a particular data set which may describe, for example, how, when, and by whom it was received, created, accessed and/or modified and how it is formatted.

- Describes the content, quality, condition and other characteristics of the data.

- Metadata is vital in helping potential users to find needed data and determine whether a data set will meet their needs before they spend the time and money to obtain and process it. 

- It is important for: 

• Data browsing/previewing
• Data transferring
• Data Documentation
• Data Searching

- Identification / Title

- Data Quality

- Spatial Data Organization (Publisher/Creator)

- Spatial Reference

- Entity and Attribute 

- Distribution 

- Contact 

- Metadata Reference 

- A variety of free and commercial software tools available to support metadata development

- Tools for creating and editing metadata: Freeware/shareware, ArcCatalog

- Metadata should be created to meet certain standards about structure and contents

- The Content Standards for Digital Geospatial Metadata (CSDGM)

Satellite Constellation (Space Segment)

Ground Control Network (ground segment)

User Equipment (User Segment)

- 24+ NAVSTAR satellites

- Orbit: 20,200 km above the Earth

- continuously broadcast position and time data

- First satellite launched in 1978

- full constellation of 24+ satellites in operation in 1994

- At least 4 satellites are visible anytime, anywhere

- Most locations usually have 6 to 8 satellites available

- Each satellite makes roughly two revolutions per day

- Maintains the system through five monitoring stations and a master control station at Shriver Air Force Base, Colorado

- These stations correct orbit and clock errors

- GPS sattelites circle the earth twice a day in a very precise orbit and transmit signal information to earth

- GPS receivers take this information and use triangulation to calculate the user's exact location 

- The GPS receiver can help determine locations on the Earth's surface by collecting signals from three or more sattelites through a process called triangulation 

- Three spheres are necessary to find position in two dimensions

- Four are needed in three dimensions

- Ionoshpere and Troposhere delays: signal slows as it passes through atmosphere

- signal multipath: signal is reflected off of tall buildings or rocks

- receiver clock errors: not as accurate as atomic clocks

- orbital errors: inaccuracies of reported location

- Taking multiple measurements at the same location and then calculate the average

- Differential correction (DGPS)

Differential Global Positioning System

What: enhancement to GPS that a network of fixed ground based reference stations to broadcast the difference between the positions indicated by the sattelite systems and the known fixed positions

How it works:

These stations broadcast the difference between the measured satellite pseudoranges and actual (internally computed) pseudoranges, and receiver station may correct their pseudoranges by the same amount; basically uses a reference system

Why: DGPS accuracy and integrity are better than GPS

- Central application in the ArcGIS Desktop

- Used for all map-based tasks including cartography, map analysis and editing

- working with maps that each have a page layout containing a geographic window or view with a series of layers, legends, scale bars, north arrows and other elements

- offers a different way to view a map (a geographic data view and layout view) in which you can perform a broad range of advanced GIS tasks

- application helps you to organize and manage all of your GIS data

- includes tools for browsing and finding geographic information, recording and viewing metadata, quickly viewing any dataset, and defining the schema structure for your geographic data layers

- simple application containing many GIS tools used for geoprocessing

- two versions: complete version with ArcInfo and the lighter version that comes with ArcView and ArcEditor software

- lighter version contains over 20 commonly used tools for data conversion and management

- complete version comes with a comprehensive set of tools (over 150) for geoprocessing, data conversion, map sheet management, overlay analysis and map projection

- Topographically Integrated Geographic Encoding and Referencing System (TIGER)

- Digital Line Graphs (DLG)

- Digital Elevation Model (DEM)

- Digital Orthophoto Quadrangles (DOQ)

- Spatial and tabular data are collected simultaneously 

- Position accuracy is superior to conventional methods

- Coordinate systems and reference datums can be easily changed in the field and in the processing software

- GIS conversion is simple, can put GPS data into GIS easily

- Data collection costs are lower than conventional methods 

- Feature visual inspection is possible while gathering data 

- Data gathering is possible 24 hours a day, seven days a week

- GPS is unaffected by weather

- Requires training and retraining as technology changes

- Urban canyon buildings can block satellite signals 

- Heavy foliage and thick branched trees can attenuate and/or block satellite signals

- Multi-path reflective signals can make date inaccurate, signals can bounce

- Requires careful attention to system configuration and date collection standards and procedures