a collection of facts or figures that pertain to places, people, things, events, concepts

Information

processed or value added data that have certain perceived values to a user or a community of users

Knowledge

transformation of data into information is an explicit act by a user to raise their ___ to a level appropriate for specific decision making purposes

Intelligence

When a user deploys knowledge to perceive relationships, formulate principles, and introduce personal values

System

1. formed or constructed to achieve certain basic objectives or functions

2. their continuing existence depends on their ability to satisfy the intended objectives-if this ability fails or starts to decline, systems concerned must be upgraded or replaced

3. individual system is composed of many interrelated parts which may be operational systems by themselves

4. these parts operate individually and interact with one another according to certain rules of conduct such as procedures, laws, contractual agreements, and accepted behavior

Information Systems

1. is set up to achieve the specific objectives of collecting, storing, analyzing, and presenting information in a systematic manner.

2. structurally is made up of interrelated components that include a combination of data and technical and human resources

3. being made up of input, processing, and output systems, all working according to a well-defined set of operational procedures and protocols.

4. can be operated independently and at the same time linked with other information systems

Information System Network

The data and technical and human resources used to form the system

communications protocol and data management procedure

functional subsystems

stand-alone or network mode of systems or network mode of systems configurations

Nonspatial Information systems

those designed for processing data that are not referenced to any position in geographic space. For example, a system for accounting.

Spatial Information Systems

those designed for processing data pertaining to real-world features or phenomena that are described in terms of locations

True/False

All Spatial information systems can be regarded as GIS

False

CAD systems, CAM systems are also spatial information systems

True/False

Only those spatial information systems that are ussed for processing and analyzing geospatial data or geographically referenced data can be labeled as a GIS

True

Geospatial Data

Characterized by geographic space

Representation at geographic scale

Geographic Space

data are registered to an accepted geographic coordinate system of Earth’s system so that data from different sources can be spatially cross referenced

Geographic Scale

data are normally recorded at relatively small scales and must be generalized and symbolized

Land Information Systems (LIS)

Land Related Information Systems (LRIS)

focus of the system on land related activities such as ownership, tax assessment, land and water resources

Geographic Information Science

set of basic research issues raised by the handling of geographic information that include geographic data, problem solving, and using geographic information on society

Aims to provide the theoretical and organizational coherence for the scientific study of geographic information

True/False

Canada produced the first ever GIS

True

True/False

GIS was application driven during the 1960’s-70’s- built to meet specific information needs of individual organizations

True

Topology

refers to the spatial relationship of adjacenc, connectivity, and containment among topographic features

Impacts of Topology

solved data representation problem that hindered GIS in the early years

reduced the complexity of applying geographic data for spatial analysis, thus making GIS easier to use

geospatial data can be stored in a simple structure that is capable of respresenting their attributes

ESRI

created ArcInfo released in 1982

vector based GIS to use georelational data model that employed hybrid approach to geographic data processing

graphical data stored using topological data structure, while attribute data are stored using relational or tabular data structure

GIS 1980s-1990s

shifted to data oriented approach of GIS development fundamentally changed the way GIS technology had been developed

designed to meet demand of corporate business goals

enterprise Computing environment

integration of geographic data with other type of business data

Information infrastructure

emerged in early 1990s when U.S. proposed Nation information Initiative

intended to provide access to information affecting their lives that pertains to governement, health care, education, and community development

Location Based Service (LBS)

LBS makes use of the information about the location of the mobile computer to deliver personalized, localized, and real time geographic services to the user.

Safety Services

enhanced 911 capable of identifying the location of the user in case of emergency

information services

traffic information, navigation assistance, yellow pages, and travel/tourism information

Enterprise services

vehicle tracking, logistic planning, utility asset inspection and management

consumer portal services

delivery of local news, weather report, and forecast, driving directions

Telematics services

using GPS technology to obtain real time location information to provide driving directions and vehicle tracking functionality in fleet management

triggered location services

including location senstive advertising, billing, and logistics

Location Awareness

obtaining location based information by means of coordinates

Components of GIS

data

technology

application

people

Geospatial Data

can be categorized into

geodetic control network

topographic base

graphical overlays

Geodetic Control Network

foundation of all geographic data

provides goegraphical framework by which different sets of geospatial data can be spatially cross-referenced with another

established by high-precision surveying methods and vigorous computation at the national or contintal level.

Topographic Base

created as the result of a basic mapping program by national state/ provincial, and local government mapping agencies

land surveying and phtogrammetry

Graphical Overlays

thematic data pertaining to specific GIS applications

overlays of physical features can be derived directly from the topographic base

can be collected by site investigation

Vector

data that depict the real world by means of discrete points, lines, and polygons

Raster

Data depict the real world by means of a grid of cells with spectral or attribute values

not good for representing individually identifiable features but is ideal for a variety of spatial analysis functions

Surface Data

depict the real world by means of a set of selected points or continuous lines of equal vales and can be analyzed and displayed in two or three dimensions and are most suited for natural phenomena

GIS Database

can be formed by aggregating one or more geodatabases, usually organized into broad categories such as land use, transportation, hydrology, environment, and utility

Hardware

made up of a configuration of core and peripheral equipment that is used for the acquisition, storage, analysis, and display of geographic information.

Central Processing Unit (CPU)

perfoms all the data processing and analysis tasks and controls the input/output connectivity with data aquisition, storage, and display systems

Conventionally GIS

were developed as tand alone applications that ran on a single host computer, but todays GIS are mostly implemented in a network environment using the client/server model.

Server

the computer on which the data and software aer stored

Client

computer by which users access the server

Software

GIS conventionaly developed using a hybrid approach that handled graphical and descriptive components of geospatial data separately

geographical data engine

a proprietary of GIS software that handled graphical data

Georelational datamodel

connection between the graphical data engine and the database management system (DBMS)

data mining

allow users to identify facts about the real world and transform these facts into geographic objects useful for geospatial data processing and analysis

The use of object oriented technologies

has transformed GIS from automated filing cabinets of maps into smart machines for geographic knowledge

toolbox approach

allows for users to customize their applications by using scripting language to build software extensions

component software

software engineering methodolgy that has been evolving since the early 1990s, addresses the integration of separate computer based applications such as document imaging, optical character recognition, database query.

GIS as a field of academic study

Cartography

remote sensing

mathematics

statistics

computer science

information technology

geography

urban planning

resource management

GIS as a branch of information technology

cartography

remote sensing

computer programming

software-specific training

workshops

laboratories

GIS as a data institution

information technology

law

sociology

antrhopology

cognitive science

economics

political science

public administration

Geographic Scale

Scales of interest to human activity/interaction. Refers to spaces concerning the Earth’s surface or near-surface

Spatial Scale

Can refer to a theoretical or mathematical space and can thus be applied to all spaces and scales, real and otherwise

Geographic Space

The commonality of both the data and the problems that the systems are developed solve is geography, i.e. location, distribution, pattern and relationship within a specific geographical reference framework

Geographic Scale

data usually recorded at relatively small scales and must thus be generalized and symbolized

Define GIS

GIS is a collection of hardware, software, data, policies, procedures, and people for the input, storage and retrieval, manipulation and analysis, output and modeling of spatially referenced data

Pacel Based LIS

emphasis on landownership and other castral applications. lands divided into parcels that have legal descriptions

non-parcel bassed LIS

natural resources IS, used for habitat/wildlife evaluation and management, flood hazard mitigation, conservation easement, etc.

What is not a GIS?

CAD, CAM, CAC

automated mapping

Database Management Systems (DBMS)

Types of GIS Software Packages

Grass

ArcInfo

ArcMap

IDRISI

Computing planar distance using distance theorem

d-v(x2-x1)^2 + (y2-y1)^2

where X2-x1 = difference in longitude

where y2-y1 = difference in latitude

D = distance between two points

Communication Paradigm

assumed that map itself was a final product designed to communicate a spatial pattern via symbols, class limit determinations etc.

Analytical paradigm

maintains raaw data in computer storage device for subsequent analysis – GIS

Map

generalized view of an area as seen from above typically reduced in size

cartography

subfield of geography that focuses on map-making

scale

ratio of map units to ground units

projection

process of transforming spherical Earth to flat map

Map Projections

can be perspective or nonperspective

Perspective Map projection

strictly geometric, use of a point of origin, or viewpoint, and a surface of projection. viewpoint selected baased on a certain critieria

Nonperspective Map Projection

modifying the perspective projection to maintain desired properties – Ex. Mercator Map

Map projections

can be expressed according to generalized functional relationships between geographical coordinates of a point on the Earth’s surface and the coordinates on the plane

Properties of Globes

parallels are always parallel to each other, meridian converge at poles and are evenly spaced along any parallel; distance between parallels decreases towards poles

Map projection properties

area

shape

distance

direction

Shape

to maintain shape make the scale along the meridian and paralell the same in both directions

preserving shaped distorts the distances

Meridians

intersect parallels at right angles

Area

shows spatial distributions and relative sizes of spatial features

tradeoffs of preserving area are the shape distance and occasionally directions are distorted

true direction

inherent property of azimuthal class projections since all meridians pass through the pole

Conformal Projection

naturally preserves shapes and true direction

Mercator Projection

Gerardus Mercator

Cylindrical projection

true shape

meridians equally spaced

rhumb lines enable plotting direction (good for navigation)

Disadvantages of Mercator Projection

midlatitude and poleword landmasses dramatically stretched

Classes of Projection

Cylindrical

conical

planar

Cylindrical Projection

cylinder assumed to circumscribe a transparent globe such that a cylinder touches the equator throughout its circumference

meridians are vertical and parallel lines

parallels are horizontal straight lines

Conical Projections

come placed over globe such that the apex of the cone is exactly over the polar axis

cone must touch globe along a parallel of latitude

along standard parallel, scale is correct

parallels are arcs of circles

Planar or Azimuthal Projections

Plane Touches the globe at North or South Pole

Like a cone flattened until vertex reaches a limit of 180 degrees

shape is circular

meridians look like straight lines eminating from the circle

parallels are complete circles centered at the pole

Universal Transverse Mercator (UTM)

used to define horizontal positions world wide 6 degree zones each mapped by transverse Mercator Projection

Fuller Transformation

preserves land masses

very little distortion in both shape and area

no more than 2% error

Defining Projections in Arc/Info

for coverages, tins and grids projection information is stored as a PRJ file within their subdirectory and store as a file name .prj

Cover

projection information is written to the PRJ of a coverage

Grid

projection information is written to the PRJ of a grid

File

projection information is written to the PRJ of an ASCII text file

TIN

projection information is written to the PRJ of a tin

;target;

data set for which the projection information is being defined

Georeferencing

the representation of the location of real world features within the spatial framework of a particular coordinate system

objective

provide a rigid spatial framework by which the positions of real-world features are measured, computed, recorded, and analyzed

geoid and ellipsoid

deal iwth representing the physical shape of the Earth via a mathematical surface

Ellipsoid

the reference surface for horizontal positions

physical shape of the real earth is closely approximated by the rotational ellipsoid

reference surface for horizontal coordinates (lat/long)

f = (a-b)/ a

Amount of polar flattening

where a and be are lengths of major and minor semi axes of the ellipse

Eccentricity

e^{2}= (a^{2}-b^{2})/ a^{2}

Geoid

means earthlike

shape of the earth if oceans were allowed to flow freely under the continents

geoid rises over the continents and is depressed over the oceans

coincides with mean seal level

reference surface for vertical coordinates

equipotential surface

surface on which the gravity potential is constant everywhere

Datum

model that describes the position, direction, and scale of relationships of a reference surface to positions on the surface of Earth

Geodetic datums

established to provide positional control that supports surveying and mapping projects covering large geographic areas

provide positional control that supports surveying and mapping projects covering large geographic areas

vertical datum

zero surface from which all elevations or heights are measured

MSL was used as a vertical datum since MSL is available worldwide

Geocentric Datum

referenced by 3-D cartesian coordinate systems (x,y,z) with the origin coincident with the center of the ellipsoid

Relation b/w Coordinate Systems and Map Projections

coordinate systems formed on the basis on map projections but they are not map projections themselves

coordinate systems and map projections are different concepts with different purposes

map projections define how poisitons on Earth’s surface are transformed onto a flat map surface

the coordinate system is then superimposed on the surface to provide a referencing framework by which positions are measured and computed

Universal Transverse Mercator

projection is used to define the horizontal positions into 6 degree zones, each mapped by the Transverse Mercator projection with a central meridian in the center of the zone

Spatial Relationships

Topological Relationships

continguity- next to sharing a border

connectivity – connected to, allowing flow from one to the other

proximity- near

closure contained

Spatial attributes

always interested in location

Non-Spatial Attributes

easily handled by non-spatial databases

spatial attributes and relationships are not handled well by non-spatial databases

Spatial Data Aquisition

Land Surveying

Remote Sensing

Global Positioning System

Geographic Data Collection

ground surveys

tape measures

LIDAR

Global Position Systems (GPS)

U.S. DoD project devised in 1970s

constellation of 24 satellites

6 orbital planes

55 degree inclination

receiver computes position, velocity, time, four GPS satellites used to calculate position in 3 dimensions to offset receiver clock errors

Radio Frequency Identification (RFID)

Can be passive or active

can range from few cms to 20-30 ft

high powered tags can tansmit into low orbit

Point of sale terminals used for customer tacking

RFID

Can be virtually undetectable

can be woven into materials

uses a 96-bit code as a string of 96 zeroes and ones

Examples of GIS

Digital Raster Graphic (DRG)

Digital Line Graph (DLG)

Digital Elevation Model (DEM)

LiDAR derived elevation data

Non spatial Data for Thematic Mapping

Geographic referencing for attribute data uses the hierarchical referencing system

discrete often parcelled based

municipal addresses

Non Spatial Levels of Measurement

usually determined by the valid operations

numerical levels

Steven’s Levels of Measurement

Binary Scale

Nominal Scale

Ordinal Scale

Interval Scale

Ratio Scale

Binary Scale

presence or absence. frequently used to represent discrete data in raster systems

Nominal Scale

making distinctions in kind/class category

Ordinal Scale

Difference in Rank

can go beyond just equal or not equal

sorting is possible

non parametric/ qualitative

Interval Scale

uses a relative scale, zero is arbitrary and can have negative values

Ratio Scale

uses an abosolute zero. zero represents the absence of phenomena

Criticism of Steven’s levels of measurement

not adequate to address all possible circumstances in cartography and GIS

ratio is not the highest level of measurement

cyclic measures do not fit the concept of scale well

Data Dictionary

defines our terms, levels of measurement, translates computer representation or attributes.

Data entry

Manual coordinate capture

attribute capture

digital coordinate capture

data import

Editing

manual point, line, and area feature of editing

manual attribute editing

automated error detection and editing

data management

copy, subset, merge data

versioning

data registration and projectiong

summarization, data reduction

documentation

Analysis

spatial query

attribute query

interpolation

connectivity

proximity and adjacency

buffering

terrain analysis

boundary dissolve

spatial data overlay

moving window analysis

map algebra

Output

map design and layout

hardcopy map printing

digital graphic production

export format generation

metadata output

digital map serving

Cartography

historically cartographic products from GIS not Good

Digital Maps (soft copy)

human computer interaction

optimization of communication and presentation of geographic information

Computational Steering

user views intermediate results of spatial analysis and based on those results, the algorithmic parameters may be interactively changed

Isarithmic Mapping

mapping a real or conceptual 3-D geographical volume with quantitative line symbols. It is a planimetric representation of a 3-D volume

Two forms of Isarithmic Maps

Isometric

Isoplethic

Both involve the planimetric mapping of the traces of the intersections of horizontal planes with the 3-D surface

Isometric Maps

generated from point data

Actual – measure with instruments or other point sampling techniques

Derived- statistiacal measures and magnitudes

Isoplethic Maps

generated from mapping data that occured over geographic areas called unit series

Isarithmic Map Construction

magnitude or value of this isarithmic lines represent their vertical distance from teh data

planes constructed parallel to the Datum – each isarithm will have a constance magnitude, distance from the datum

When to use Isarithmic Maps

mapped data must be a geographical volume and must have a surface that bounds the volume

based on the principle in geography that things closer together are more similar

if considering a location with no measured valuek IDW will look within a specified neighborhood around the point of interest and identity of the measured value

the closer observations will influence the predicted value more than observations measured farther away

closer points are thus more heavily weighted than points further away.. IDW as the distance from the point-to be predicted increase the values become more inversely wieghted

Inverse Distance Weighted Interpolation

Advantages

results in a smooth and continuous surface that changes between observations

derived surface passes through observed values

Disadvantages

requires subjective selection of parameters

does not interpolate beyond min and max values in observation sets

Design Process

Graphic design produces visual forms

assign qualitative and quantitative meaning s to the distinctive marks – relate graphic characteristics of the marks to attributes of the data

arrange the marks in a total composition that enhances map communication with teh user, wehre the intended information is conveyed

skill and artistry important for map design

Criteria for a Good Decision

should be suited to the needs of map users

should be easy to use

should be accurate, present information without error and distortion

should be clear, legible, and aesthetically pleasing

symbols, color, layout, and typographic appearence

should be thought provoking and communicative

Design of Symbols

Class of symbols

point, line and area polygon symbols are the basic elements used to create all visual design

Point

conveys a positon

Line

exhibit directions as well as position

Area

exhibits exten, direction, and position – graphically uniform over the area; even color uniform repetition of a point or line symbols

Shape

regular or geometric shapes, irregular shapes as well

Size

different geometric dimensions

Color

hue, value, and saturation

Pattern

combination of basic reptitive graphic elements produces an aerial graphic effect

Pattern

Exhibits the characteristics of arrangemetn texture/spaceing and orientation

Arrangement

shape and configuration of component marks that make up a patter

Texture

size and spacing of component marks that make up a pattern, fine texture; closely spaced small marks

Design Principles

Clarity and Legibility

Contents, Information, and Map Space

Visual Contrast

Figure-Ground Organization

Visual Hierarchy

Map Composition and Layout

Map Elements

title

Map Legend

Map scale

Map symbols

Credits

Aesthetic of Map Compositon

Visual Balance

Golden Section

it is widely accepted that a rectangle with sides having a proportion of about 3-5 seems to be the most aesthetically pleasing formats

in mathematics, a geometric proportion in which a line is divided such that the ratio of the length of the longer line segments to the length of the entire line is equal to the length of the shorter line segment to the length of the longer line segment

Typography/Lettering

used to name places; identify or label objects, provides titles, legends, and other explanatory elements

letterform characteristics, size, letter spacing typeface personalities and legibility are important aspects of lettering.

Image Draping

established technique in GIS. Draping a topographic or thematic map onto a 3-D terrain surface is effective but relies on abstract colors, shading, and symbols. Draping a satellite image such as a digital orthophoto, results in good surface texture and can produce visualizations suitable for depicting landscape-scale vegetation patterns

Geometric Video Imaging

combines video imaging techniques with geometric registration typically undertaken within a GIS. its rarely used on a production bases due to the difficulty in accurately geo-referencing the photographic video image with the 3-D perspective

VRML (Virtual Reality Modeling Language)

standard file format for representing 3-D interactive vector graphics designed particularly for use with the world wide web

Moore’s Law

the number of transistors incorporated in a chip will approximately double every 24 months.

Digital Representation of Geographic Data

Geographic Databases are dynamic, not static; allows interactive data analysis

data models; methods of data representation

Object

representation of reality, not the thing itself, it is a model

Feature

an entity being represented by an object. A defined entity and its oobject representation. this term does not make a distinction between the real thing or the model

Entity

A real world phenomneon; entities have relationships and attributes which can be spatial or non spatial

Object

discrete and definite

phenomena

distributed continuously over a large area

Representing Geographic Space

approaches to representation of real world in geographic databases;

Object based model

field based model

Spatial Relationships

contiguity – next to sharing a border

connectivity- connected to

proximity

closure/ containment

Spatial Attributes

always interested in location

Time

component of Berry’s geographic matrix

Temporal Relationships

time, algebra, measurement, relationship

Measurement of Time

Time measurement for objects can be made at an instance which is a measurement of existence

can also be made for a duration which is a measurement of evolution, occurence, and permanence

Relationship between Time and Space

spatial changes refer to geometric transformation of an object and includes the change in location, size, orientation and form

spatial relationships among objects may change as a function of geometric transformations

Temporarl Attributes of Geographic Process

Generation Time: time at which object is created

Duration Time: time during which an object is in existence or is observed

Temporal Significance: important of given event

Temporal Scale: analogous to map scale adapted to time

Logical Organization

how data are classified and feature coded to facilitate identification of relationships between data items

physical organization

method by which data items are stored on a computer

Data Classification/classification scheme

purpose of classification scheme: provide an a priori standard with which individual observations can be observed and recorded during data collection process

Two components of Classification Schemes

Descriptive Names of classes and subclasses

Definitions of classes and subclasses

Entity

spatial object that has specific properties that categorically seperate it from other entities. These properties are known as attributes

Entity class, entity type, or feature class

collectively, entities that share common attributes

Feature Codes

process of encoding the values of the entities and attributes to graphical elements during the data collection process

Feature Codes comprised of two components

Major Code

Minor Code

Major Code

identifies the entity type to which a particular entity belongs

Minor Code

Identifies the attributes that an entity has, also referred to as a attribute code

Feature codes may be

alphabetic, numeric, or alphanumeric

Precision

function of the number of bits used

Byte

smallest addressable unit in the computer, an 8-bit data item

Data Item

basic building block of data organization in the computer, an occurence or instance of a certain characteristic pertaining to an entity

Related Data Items

data items are occurrences of different characteristics pertaining to the same entity

Record

a stored record, or tuple

Data File

formed by grouping a record together

True/False

Computer processing is based on databases rather than data files

True

Raster Data Representation

Grid Cells representing areas of the same entity type have identical values or patterns of the values tend to be spatially clumped

Raster Data

run length encoding raster data compression algorithm

Raster Data Representation Encoding

Adjacent cells along a row wit hthe same values are treated as a group. Value is stored once together with the number of cells that comprise the run

Clustering

goal is to reduce seek and latency time in answering common large queries. For spatial databases this implies that objects are adjacent in space and are commonly requested jointly by queires should be stored physically together in secondary memory

Three types of Clustering for SDBMS

Internal Clustering

Local clustering; and

Global Clustering

Internal Clustering

to speed access to a single object, the complete representation of one object is stored in one disk page, assuming the size is smaller than the free space on the page. otherwise the object is stored on multiple, physically consecutive pages

Local Clustering

to speed access to several objects, a set of spatial objects is grouped onto one page

Global clustering

a set of spatially adjacent object is stored not on one but several physically consecutive pages that can be accessed by a single read request

Clustering

Design of spatial clustering techniques is more difficult than traditional clustering since there is no natural order in multi-dimensional space where spatial data resides. Also disk storage is logical and is only 1-D device

Clustering

regarding addressing systems, procedures exist to represent relative locations of the 2 or 3-D kind of 1-D sysstems

Clustering

Distance preserving manner needs to be mapped from higher dimensional space

No two points in the space are mapped onto the same point on the line, and should be one to one

Row order (TV)

total longer path than row prime sequence, every other line is traversed in a reverse direction and have several placves in which neighbors on the path are not adjacent in space

Diagonal and spiral orders

like the row prime sequence in possessing the property of immediate adjacency

Diagonal Sequence

mixes up corner and side joins

Spiral Order

Terminates in the middle, making it impossible to connect other blocks of space

Comparison of Paths

Total length of the path

variability in unit lengths, where unit length is the distance from one point on the path to the next sequence;

the average distance on the path from the tiles to their neighbors in space

Space Filling curves

Special fractal curves which have characteristics of completely covering an area or volume

topological dimension of 2

if point is 0-D, not possible to define a 1-D curve passing thru the infiinity point

if point is conceptualized as 2-D square the side of which tends toward zero, it is possible to find a curve filling a 2-D space

In 3-D a point can then be defined as a small cube for which the side length tends toward zero and the curve as a 3 D curver

Paths as Space Filling Curves

curve must pass only once to every point in multidimensional space

two points that are neighbors in space must be neighbors on the curve

two points that are neighbors on the curve must be neighbors in space

it should be easy to retrieve neighbors at any point

curver corresponds to a mapping from a multi- to a 1-D space

curve should be able to be used for variable spatial resolution

curve should be stable

Peano or N ordering

facilitates retrieving neighbors; while neighboring points in space are not always neighbors on the curver, they usually are

Hilber Curve

passes through all points in a set by means of single length steps only. it meets many of the criteria of an ideal curve, but does not enable the easy retrieval of neighbors. Unstable

Algorithm for the Z curve (peano)

Read the binary representation of the x and y coordinates

Interleave the bits of the binary numbers into one string

Calculate the decimal value of the resulting binary string

Algorithm for the Hilbert Curve

Read in the n-bit binary representation of the x and y coordinates

interleave bits of the two binary numbers into one string

divide the string from left to right onto 2-bit strings

give decimal valu, d for each 2 bit string

for each number j in the array i

convert each number in the array to its binary representation, concatenate all the strings in order from left to right, and calculate teh decimal value

Disk access

Hilbert curvbe method is slightly better than the Z-curve because it does not have any diagonal lines

Block

square region that is the result of one or more quadtree subdivisions of the original image. a quadtree recursively subdivides space into four equal parts

Handling regions

Each object can be uniquely representaed by the Z-values of its blocks, Each such z-Value can be treated as a primary key of a record of the form

Space Filling curves for GIS systems

Make scanning operations more efficient (hardware devices or scanning thru datafiles)

They are used as spatial indexes, simplifying 2-D addressing as 1-D addressing

Vector Data Representation

Vector Data model is object based

best utilized to represent discrete objects

spatial objects are represented individually and represented mathematically, via coordinates

Vector data model is more complex than raster data model

Wide variety of formats

Vector Data Representation Formats

Decomposing spatial objects into basic graphical elements

use of topology (spatial relationships) as well as geometry coordinates

Vector Terminology

Lines (arcs)- begin and end with a node

Polygons (areas) – closed loop of coordinates

points

Spaghetti data model

not structured vector data from map digitizers, CAD- stores graphical elements, not graphical entities

redundant- stored twice

must be structured for use in GIs

Topological Data Model

Structured vector data

many variants of model – most common is the arc-node data model

Arc = line segments

node = end points of line segments

stores graphical elements rather than graphical entities

stored topological relation allows graphic entities to be constructed

Spatial Data Transfer Standard (SDTS)

robust way of transferring earth referenced spatial data between dissimilar computer systems with the potential for no information loss. it is a transfer standard that embraces the philosophy of self-contained transfers, spatial data, attribute, goereferencing, data quality report, data dictionary

Classification and intended use of objects in STPS

Geometry only – for drawing, display and geometrically defined operations on raster and vector data structures

geometry and topology – for vector data structures that use geometric drawing and topological operations

topology only – for certain analytical operations

Point

a zero dimensional object that specifies geometric locations

Entity point – point used for identifying the location of point features such as tower, buoys

Label Point – a reference point used for displaying map and chart text to assist in feature identification

Area Point- representative point within an area usually carrying attribute information about that area

Node

zero dimensional object that is a topological junction of two or more links or chains, or an end point of a link or chain

Line and Line Segment

A line is a generic term for a one dimensional object

Line segment- direct line between two points

String

connected nonbranching sequence of line segments specified as the ordered sequence of points between those line segments. A string may intersect itself or other strings

Arc

a locus of points that froms a curve that is defined by a mathematical expression

Link

a topological connection between two nodes. A link may be directed by ordering its nodes

Chain

a directed nonbranching sequence of nonintersecting line segments and arcs bounded by nodes, not neccesarily distinct at each end

Complete Chain

chain that explicity references left and right polygons and start at the end of nodes it is a two dimensional manifold

Network Chain

chain that explicitly references start and end nodes and not left and right polygons

Ring

sequence of nonintersecting chains or strings and or arcs with closure. a ring represents a closed boundary, but not the interior area inside the close boundary

Interior Area

Area not including its boundary

G-Polygon

area consisting of an interior area, one outer G ring and zero or more non intersecting nonnested inner G-rings. No ring, inner or outer, must be collinear with or intersect any other ring of the same G-polygon

GT polygon

area that is two dimensional component and only one two dimensional maniforld

Universe polygon

defines the part of the universe that is outside the perimeter of the area covered by other GT-polygons. This polygon completes the adjacency relationships of the perimeter links

Pixel

two dimensional picture element that is the smallest nondivisible element of a digital image

Grid Cell

two dimensional object that represents the smallest nondivisible element of a grid

Two dimensional aggregate spatial objects

Certain two dimensional aggregate spatial objects must be defined to provide context for many of the simple objects defined above. these aggregate objects are necessary for the definition of raster objects, topology

Digital Image

Two dimensional array of regularly spaced picture elements (pixels) constituting a picture

Grid

two dimensional set of grid cells forming a regular tesselation of a surface

Rectangle variant Grid

Each row and column of the Grid may have independent thickness or width

Layer

an areally distributed set of spatial data representing entity instances within one theme, or having one common attribute or attribute value in an association of spatial objects. A layer is specifically a two, three, or N-dimensional array of attribute values associated with all or part of a grid, image, voxel space or any other type of raster data.

Raster

one or more related overlapping layers for the same grid, digital image, voxel space, or any other type of raster data. the corresponding cells between layers are registered to the same raster object scan reference system . The layers overlap but need not be of the same spatial extent

Graph

set of topologically interrelated zero-dimensional, one dimenional and sometimes two dimensional objects taht conform to a set of defined constraint rules

Planar Graph

node and link or chain objects of the graph occur or can be represented as though they occur upon a planar surface. Not more than one node may exist at any given point on the surface

Network

a graph without two dimensional objects. If projected onto a two-dimensional surface, a network can have either more than one noede at a point, and intersecting links or chains without corresponding nodes

Voxel

a three dimensional object that represents the smallest nondivisible unit of a voxel of space (volume) (think cube)

Voxel Space

3 D array of voxels in which the volumetric dataset resides. The volume represents some measurable properties or independent variables of a real object or phenomenon.

MetaData/MetaInformation

documents knowledge of data accuracy, provenance, and age necessary for good decision making

can build a GIS catalog, internal or external portals allow others to search, find, and access the GIS resources

FGDC

Federal Geographic Data Committe with the goal to provide a complete description of a data source

ISO

International Organization for Standardization

attempts to satisfy the requirements of all existing metadata standards; flexible genearl or detailed descriptions

XML

eXtensible Markup Language was developed by the World Wide Web Consortium

standard for designing text formats

GIS

A GIS is a collection of hardware, software, data, policies, procedures, and people for the input, sotrage, & retrieval, manipulation and analysis, output and modeling of spatially referenced data

Relational DBMS

object oriented database systems

Small World

GIS FAct

Sometimes referred to as a scaleless system but it is not true because you are not changing the original scale that the data was originally collective

Cognitive GIS

deals with non-euclidean coordinates

Error Propagation

can amplify or cancel out your operations. Understanding how errors propagate is extremely important

Digital Raster Graph (DRG)

scanned hardcopy map that has been georeferenced

Line

Graphical

Chain/arc

topological

Differential Post Processing

Most accurate form of GPs

Projection Surface

Plane (flat surfaces) – azimuthal projection family

cylinder – cylindrical projection family

Cone – Conic projection family

Light Source Position

Gnomonic- Light source is at the center of the globe (flashlight shing at the center)

Stereographic: light source is at the point exactly opposite of the point of tangency of the projection surface (from the poles)

Orthographic- at a considerable distance (infinite point): Light rays are parallel, often used for persepctive views which means the map is often perspective but not conformal or equal in area.

Normal (regular Projection)

normal orientation for a plane is tangent at the pole (polar azimuthal)

cylindrical is normally oriented so that it is tangent along equator (equitorial)

A cone is normally oriented so that it is tangent along a parallel with its apex over the pole, in alignment with the axis of rotation

Transverse Projection

projection is tuned 90 degrees from normal

for a plane, the plane is tangent at the equator

for a transverse cylindrical projection, the cylinder is tangent along a meridean

transverse conic: not frequently seen

Oblique Projection

Projection surface lies at an angle somewhere between the normal and transverse position

Tangent Projection

The projection surface is tangent to the globe

a planar surface is tangent to the globe only at one point

tangent cones and cylinders contact, the globe along a line

Secant Projection

projection surface intersects the globe instead of merely touching the surface

a planar surface intersects the globe forming a small circle along the intersection line

A cone or cylinder intersects the globe resulting in two small circles along intersecting lines

Standard Point

point at which a planar surface touches the globe

only the one standard point exists for a planar tangent projection

directions from the point are accurate greate circles passing through are represented as straight lines

Distortions of area angle have a circular pattern and increases with distance from standard point

Standard line (line of true scale)

line along which projection surface touches or intersects the globe

this is the one standard line when a polar surface intersects the globe or a cone or cylinder is tangent to the globe

there are two standard lines when cone or cylinders intersect the globe

along a standard line a map has no distortions and map scales is identical to the nominal globe

Geometric distortion generally increases with distance

Geodemographics

demographic information about a population that is spatially consolidated

Exact Interpolators

honor the data points upon which interpolation is based

surface passes through all points whose value is known

proximal interpolation, R splines and Krigin methods all honor given data points

Kriging may incorporate a nugget effect if so not exact interpolator

Approximate Interpolators

used when uncertainty exists about given surface values

utilize belief that in many data sets there are global trneds which vary slowly, overlain by local fluctuations which very rapidly produce uncertainty (error)

Effect of smoothing will therefor reduce effects of error on resulting surface

Stoichastic Interpolators

incorporate concept of randomness

interpolated surface is conceptualized as one of many that might be observed all of which could have been produced with known data points

Kriging is stoichastics because it allows statistical significane of the surface and uncertainty of predicted values to be computed

Deterministic Interpolators

do not use probability theory

example: TIN linear

Fuzzy Math

fuze up, precision up, knowledge up, and is easier to work with

Toblers Law of Geography

Things closer together in space tend to be more similar than things further apart

Kriging Interpolation Method

geostatistical

basis of the method is the rate at which the variance between point changes over space, this is expressed in the variogram which shows how the average difference between values at points changes with distance between points

requires characterization of spatial data to set parameters

usually more accurate

CAD Models

RGB

most applicable to computer display devices

additive based on a mixture of Red, green, blue

CAD system viewed as a cube with red green and blue dyes

Red + Green = Yellow

Red + Blue = Magenta

Green + Blue = Cyan

Red + Green + Blue = white

None = black

HSV Model

tecktronic developed by HSV system to specify selection of color projection from tints to shades

double cone with the central axis forming a lightness progression identical to black and white diagonal line through RGB cube

Many color graphic programs specify color based on hue, lightness value, and saturation

HSV Color Model

Hue is given as an angle counter clockwise between 0 and 360

lightness value is given as an integer between 0 (black) and 100 (white) and saturation between 0 (gray) and 100 (pure color)

triangular slice for each hue can also be viewed as a plane cut from the RGB cube and deforemed into the HSV triangles

The transformation is linear- simple equations can be used to transforms HSV specifications into RGB and vice versa

RGB to HSV

colors in the HSV are defined with respect ot normalized red, green, and blue values