Advanced GIS – Flashcards

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

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

• 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

False

CAD systems, CAM systems are also spatial information systems

• Characterized by geographic space
• Representation at geographic scale

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

• 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

• 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

• 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

• 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

• data
• technology
• application
• people

can be categorized into

• geodetic control network
• topographic base
• graphical overlays

• 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.

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

land surveying and phtogrammetry

• 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

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

• Cartography
• remote sensing
• mathematics
• statistics
• computer science
• information technology
• geography
• urban planning 
• resource management

• cartography
• remote sensing
• computer programming
• software-specific training
• workshops
• laboratories

• information technology
• law
• sociology
• antrhopology
• cognitive science
• economics
• political science
• public administration

• CAD, CAM, CAC
• automated mapping
• Database Management Systems (DBMS)

• Grass
• ArcInfo
• ArcMap
• IDRISI

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

• area
• shape
• distance
• direction

• to maintain shape make the scale along the meridian and paralell the same in both directions
• preserving shaped distorts the distances

• shows spatial distributions and relative sizes of spatial features
• tradeoffs of preserving area are the shape distance and occasionally directions are distorted

• Gerardus Mercator 
• Cylindrical projection
• true shape
• meridians equally spaced
• rhumb lines enable plotting direction (good for navigation)

midlatitude and poleword landmasses dramatically stretched 

• Cylindrical
• conical
• planar

• 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

• 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

• 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

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

• preserves land masses
• very little distortion in both shape and area
• no more than 2% error

projection information is written to the PRJ of a coverage

• 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)

Amount of polar flattening 

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

• 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

• 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

• zero surface from which all elevations or heights are measured
• MSL was used as a vertical datum since MSL is available worldwide

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

• 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

• Topological Relationships
• continguity- next to sharing a border
• connectivity - connected to, allowing flow from one to the other
• proximity- near
• closure contained

easily handled by non-spatial databases

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

Land Surveying

Remote Sensing

Global Positioning System

• ground surveys
• tape measures
• LIDAR

• 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

• 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

• Can be virtually undetectable
• can be woven into materials
• uses a 96-bit code as a string of 96 zeroes and ones

• Digital Raster Graphic (DRG)
• Digital Line Graph (DLG)
• Digital Elevation Model (DEM)
• LiDAR derived elevation data

• Geographic referencing for attribute data uses the hierarchical referencing system
• discrete often parcelled based
• municipal addresses

usually determined by the valid operations

• numerical levels

• Binary Scale
• Nominal Scale
• Ordinal Scale
• Interval Scale
• Ratio Scale

• Difference in Rank
• can go beyond just equal or not equal
• sorting is possible
• non parametric/ qualitative

• 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

• Manual coordinate capture
• attribute capture
• digital coordinate capture
• data import

• manual point, line, and area feature of editing
• manual attribute editing
• automated error detection and editing

• copy, subset, merge data
• versioning
• data registration and projectiong
• summarization, data reduction
• documentation

• spatial query
• attribute query
• interpolation
• connectivity
• proximity and adjacency
• buffering
• terrain analysis
• boundary dissolve
• spatial data overlay
• moving window analysis
• map algebra

• map design and layout
• hardcopy map printing
• digital graphic production
• export format generation
• metadata output
• digital map serving

• historically cartographic products from GIS not Good
• Digital Maps (soft copy)

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

• Isometric
• Isoplethic

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

generated from point data

Actual - measure with instruments or other point sampling techniques

Derived- statistiacal measures and magnitudes

• 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

• mapped data must be a geographical volume and must have a surface that bounds the volume
• data must be continuous, not discrete
• must be familiar with the phenomenon being mapped

• Assumption is that the value at each given location is the same as teh value of the nearest observation
• Uses the concept of Thiessen Polygons
• defined around each observation 
• only one observation is contained in each polygon

• assumes values only change at the borders
• does not perform well with interval or ratio scale data because it is a continuous surface
• resulting surface is discontinuous without smooth graduations between observed values

• Assumption:
• the value of an attribute z for each unvisited grid cell location is DISTANCE WEIGHTED AVERAGE of data points located at nearby observations
• Original data points are located on a regular grid or irregularly distributed and interpolated to locations on a denser regular grid

d= distance between given and observed

z- observation point

N = number of observations

i = iteration

z1 = weighted value at a given point

T - weighting parameter

• 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

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

• 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

• 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

• Class of symbols

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

1. Clarity and Legibility
2. Contents, Information, and Map Space
3. Visual Contrast
4. Figure-Ground Organization
5. Visual Hierarchy

1. Map Elements

• 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

• 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.

• Geographic Databases are dynamic, not static; allows interactive data analysis
• data models; methods of data representation

approaches to representation of real world in geographic databases; 

• Object based model
• field based model

1. contiguity - next to sharing a border
2. connectivity- connected to
3. proximity
4. closure/ containment

• 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

• 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

1. Generation Time: time at which object is created 
2. Duration Time: time during which an object is in existence or is observed
3. Temporal Significance: important of given event
4. Temporal Scale: analogous to map scale adapted to time

• Descriptive Names of classes and subclasses
• Definitions of classes and subclasses

1. Major Code
2. Minor Code

1. Internal Clustering
2. Local clustering; and
3. Global 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

1. Total length of the path
2. variability in unit lengths, where unit length is the distance from one point on the path to the next sequence;
3. the average distance on the path from the tiles to their neighbors in space

• 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

1. curve must pass only once to every point in multidimensional space
2. two points that are neighbors in space must be neighbors on the curve
3. two points that are neighbors on the curve must be neighbors in space
4. it should be easy to retrieve neighbors at any point
5. curver corresponds to a mapping from a multi- to a 1-D space
6. curve should be able to be used for variable spatial resolution
7. curve should be stable

1. Read the binary representation of the x and y coordinates
2. Interleave the bits of the binary numbers into one string
3. Calculate the decimal value of the resulting binary string

1. Read in the n-bit binary representation of the x and y coordinates
2. interleave bits of the two binary numbers into one string
3. divide the string from left to right onto 2-bit strings
4. give decimal valu, d for each 2 bit string
5. for each number j in the array i
6. 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

1. Make scanning operations more efficient (hardware devices or scanning thru datafiles)
2. They are used as spatial indexes, simplifying 2-D addressing as 1-D addressing

• 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

1. Decomposing spatial objects into basic graphical elements
2. use of topology (spatial relationships) as well as geometry coordinates

• Lines (arcs)- begin and end with a node
• Polygons (areas) - closed loop of coordinates
• points

• not structured vector data from map digitizers, CAD- stores graphical elements, not graphical entities
• redundant- stored twice
• must be structured for use in GIs

• 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

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

• 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

• 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

• A line is a generic term for a one dimensional object
• Line segment- direct line between two points

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

• 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

• International Organization for Standardization
• attempts to satisfy the requirements of all existing metadata standards; flexible genearl or detailed descriptions

• eXtensible Markup Language was developed by the World Wide Web Consortium
• standard for designing text formats

• object oriented database systems
• Small World

1. Plane (flat surfaces) - azimuthal projection family
2. cylinder - cylindrical projection family
3. Cone - Conic projection family

1. Gnomonic- Light source is at the center of the globe (flashlight shing at the center)
2. Stereographic: light source is at the point exactly opposite of the point of tangency of the projection surface (from the poles)
3. 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.

• 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

• 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

• 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

• 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

• 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

• 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

• 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

• do not use probability theory
• example: TIN linear

• 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

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

• 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

• 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

• colors in the HSV are defined with respect ot normalized red, green, and blue values
• R= R/ R+G+B
• G= G/R+G+B
• B= B/R+G+B
• R+G+B= 1

• normalize the Saturation and Intensity to the range of [0,1] and H to the range of [0,360] 
• R = 1/3 (1-S)
• G= 1/3 (1+Scos(H)/Cos60-H
• B = 2 - (r+g)
• range of computed r,g,b is [0,1] but can be rescaled [0,255]

• almost no coordinates are stores, in fact, there only one coordinate pair that is stored - the origin
• Block orientation
• Storage

• Geometry and topology are limited but implicit in data structure
• there is no connectivity
• have contiguity built into arrangement of cells just need to know the numbering scheme and can do proximity analysis
• Index schemes - order which we are storing data into the system, z scan back and forth
• Problem: takes time to access the data we want, positions are close in space in sotrage
• type of index scheme is application dependent

• Basic Unit - Chain
• 3 Topological Objects
• Nodes - 0 dimensional connection between chains
• Chains - 1 D connection between nodes
• Polygons - 2-D polygons share chain boundaries

• nodes bound chains
• chains cobound nodes
• polygons co bound chains
• chain is basic unit since it relates to both nodes and polygons

• From Node (left poly)
• To Node (Right poly)
• Chain is given a sense of direction

ID, from node to node

topological information, deep structure

Line ID, or point poly - graphical shape info element - surface sturcture

• does not support SQL
• Fields- smallest named unit - represents a characteristic

Entity - Record, File, Database

• data fields
• money fields - allowing for only two decimal places
• integers- does not have decimal or fractional part
• reads- does have decimal or fractional part

• Primary Index into the Database
• First Field that data are stored on

• flat field
• hierarchical 
• Network
• relational
• object oriented

• a table or spreadsheet
• one file to hold all the data
• row records - number of objects
• columns - fields
• for 1 kind of object number of attributes = number of columns
• 2 kinds of objects MxN = land parcels and soil polygons

• Dead Space
• Redundancy

• Looks like a flat file
• tables or files called relations
• records are called tuples
• fields are referred to as domains

• minimizes the redundancy
• link seperate relations together by redundancy
• eliminates dead space
• process of creating a unique table/relations from redundant tables/relations called normalization

• A way to add data to a table without having to change the program used to access it
• to create a system that allows multiple user access while maintaining security

• Includes data, software/programs for storing and accessing the data as well as the security measures
• User- Query - Query Processor - transaction manager- storage manager- data metadata

• 1970s starter were most hierarchical
• 1980s relational DB model developed, algebra that describes the model and a calculus for data retrieval
• 1990s - Object oriented DBs invented
• 1997 Relational database > hierarchical - took 17 years to surpass hierarchical usage
• 2000 - relational 60% data in the market

object 5-7%, hierarchical rest of market

1. Data Manipulating Language
2. Data Definition Language

1. Logical Level
2. Conceptual Level
3. Research Area

Middleware

• connects individual DBs to other application programs; reconciles the different terms used among the various DBs
• Allows users to see at the logical level, one DB can perform just one query

• Seek Times
• Read Times
• DBs are concerned with where data are stored on the disk drive and affects retrieval time - good DBs have their own drivers to efficiently store data

• Arc Spatial Database Engine
• Relational Model 
• Examples 

• like a class = set of similar entities/objects
• represented by a rectangle

• properties of entities in an entity set
• Represented by an Oval
• So entity sets turn into tables and attributes turn into columns in the table

• connect two or more entity sets
• Represented by diamonds
• taking represents a relationship set
• think of this as a table iwth one column for each connected entity set, and one row for each list of entities are connected

• Consider a relationship between students, courses, and TAs
• if we want to know which TAs are assisting with which students this design will not tell you that

• Many to Many
• Many to One
• One to One

All of these relationships are many to many (use a round arrow to denote that drinkers have exactly one"

• many drinkers might like the same beer (many to One)