Home > Flashcards > Print Preview
The flashcards below were created by user
hcunning
on FreezingBlue Flashcards. What would you like to do?

List of GIS applications
urban planning, management policy, environmental sciences, political science, civil engineering/utility, business, education, administration, real estate, health care, defence and military

2 ways of thinking as GIS as a career:
 1. GIS professional (analyst, programmer, manager)
 2. GIS user (business manager, biologist, etc.)

5 factors that make up GIS?
 software (provides functions, tools)
 data (expensive)
 people
 methods (can be expensive, penalties if you do something wrong/against the law)
 hardware

GIS
the common ground between information processing and the many fields using spatial analysis techniques

Top 5 skills to be successful in GIS
 1. curiosity
 2. ability to work w/ data
 3. understanding geographic foundation
 4. adaptability
 5. good communications

Why do we need georeferenceing?
 navigation
 emergency response
 real estate
 courier services
 market analysis
 distribution of clients, customers, etc

Requirements for georeferencing?
 uniqueness
 interoperability (working together across organizational boundaries), persistence through time

Map scale
 ratio of distance on map to distance on ground
 large scale: better detail/resolution ex. map of town
 small scale: less resolution ex. map of country, space, big things

Geoid
 equipotential surface of the earth gravity field that most closely approximates the mean ocean level
 has physical meaning but can't be directly observed

Orthometric heights
height above sea level

Geodetic longitude
the angle bw the prime meridian and the meridian passing through the point

Geodetic latitude
the angle bw the equator plane and the normal to the ellipsoid passing through point

Geodetic height
the distance along the normal bw point 'p' and the ellipsoid

North American Datum 1927 (NAD 1927)
 many control points calculated from observations taken in the 1800s
 done manually and in sections taken over many years

World Geodetic System (WGS 1984)
 GRS 1980 almost identical to the WGS 1984 spheroid
 raw GPS data is actually reported in the WGS 1984 coordinate system

Kinds of distortions from transitioning from 3D to 2D
 area
 shape
 distance
 direction

Lambert Conformal Conic
minimal distortion near standard parallels, areal scale is reduced between standard parallels and increased beyond them

Map types
 different demands require different map types, dependant on data. maps might use:
 nominal data (names, IDs)
 categorical data
 ordinal data (seperates based on quantitative data)
 numerical data (based on #'s w/ standard interval bw them)

Common raster formats
GeoTIFF, JPEG2000, MrSID, GRID

Digital Elevation Models, 3 possible sources?
 1. aerial photography
 2. topographic maps
 3. stereostopic

Depending on the institution developing the DEM, there are several similar terms to call them:
 Digital terrain data (DTD)
 Digital terrain models (DTM)
 Digital elevation model (DEM)
 Digital terrain elevation data (DTED)

Methods to capture and store elevation grouped into 4 basic approaches:
 regular grid (points evenly distributed in a grid)
 contours (points placed along elevation lines)
 profiles (points in grid lines but grouped closer when elevation lines are closer together)
 triangular irregular networks (TIN)

TIN
 triangular irregular networks
 produced from a set of irregularly spaced elevation points, a network of triangular facets is fit to these points
 coordinate positions and elevations of each 3pts forming the vertices of each triangular facet are used to calculate terrain parameters (slope, aspect)

GPS
 Global Positioning System
 uses satellite data to calculate an accurate position on the earth, calculations relate user's position to almost any map projection within milliseconds

Trilateration
 Use of satellites for position fixing
 if the 3D position of the satellites and ranges from the satellite are known, a 3D location can be determined

GPS Configuration
 Space segment
 control segment
 user segment

Space segment
satellites provide navigation signal and relay orbital and clock data

user segment
user tracks satellite signals, downloads data, and computes position, velocity, and time

control segment
ground control tracks satellites and measures and uploads ephemeris and clock data

Toolbox perspective
an information technology which stores, analyzes, and displays both spatial and nonspatial data

The database perspective
the database system in which most of the data is spatially indexed, and upon which a set of procedures operated in order to answer queries about spatial entities in the database

The organizational perspective
A decision support system involving the integration of spatially referenced data in a problem solving environment

the functional perspective
a computerbased information system that deals with acquisition, management, manipulation, analysis, presentation, and dissemination of geospatially referenced data

Evolution of GIS software
 subroutine libraries (60s/70s)
 toolbox w/ CLI (command line interface) (70s/80s)
 taskoriented system (graphical user interface) (90s/100s)

the fundamental problem
the more you zoom in, the more complex and dynamic it gets

Conceptual methods
a theoretical construct that represents a phenomenon w/ a set of variables and a set of longitudinal and quantitative relationships b/w them

Solution to the fundamental problem: Modeling
a data model in geographic information systems is a mathematical construct for representing geographic objects

Data models
 data in GIS represents a simplified view of the real world
 defined as the relationships among objects in a spatial DB

Attribute Data
 used to record the nonspatial characteristics of an entity, aka items or variables
 help describe and define the features we wish to represent in a GIS

Nominal attributes
 variables that provide descriptive info about an object
 colour, vegetation type, city name, soil series, etc.
 no implied order, size, or quantitative info contained in the nominal attributes

Ordinal attributes
 imply rank order or scale by values
 may be descriptive such as small, medium, large, or may be numeric (classifications from 110)

Interval/ratio attributes
used for numeric items where both order and absolute difference

Levels of GIS data modeling
 reality
 conceptual model
 logical model
 physical model

conceptual models
 field based (attributes can be thought as varying continuously from place to place)
 objectbased (features can be thought of as discrete entities/objects)
 networks (objectbased, but emphasis is on the interaction bw objects along pathways)

Logical Models
 spatial or data model
 2 main types, raster (study is divided into regular cells), vector (geometric primitives like points, lines, polygons used to represent objects)

Data Compaction
 approaches to reduce storage requirements
  run length encoding
  block coding
  chain coding

Data Quality
 the totality of characteristics of a product that bear on its ability to satisfy a stated and implied need
 accuracy + precision = quality

Error
 useful to distinguish bw errors in the source data and processing errors resulting from spatial analysis and modelling operations
 as the number of processing steps increase, it becomes difficult to predict the behavior of error propagation

Data Quality Factors
 scale
 currency
 lineage
 documentation or metadata
 standards
 accuracy
 precision or resolution

Systematic error
can be rectified if discovered, because its source is understood

random error
error in measurement caused by factors that vary from one measurement to another

crossvalidations
uses all the data to estimate the trend and autocorrelation models, and to estimate how far the predicted information from actual measurements is?

validations
it uses few numbers of independent samples from the case study to estimate how perfect the estimated data is

Database Management Systems
using a specialized system, a database management system (DBMS) to manage and explore data instead of storing, managing, and exploring data directly in files

RDBMS: utilization of keys
 relations bw tables (ie entities) are represented through the utilization of keys
 super keys, candidate key, primary key, foreign key

DBMS: Advantages
 reduce data redundancy
 reduce data inconsistency
 increase data integrity
 reduce storage requirements
 ability to enforce standards
 easy to interface with
 control user privilages
 manage user needs

Relational Algebra
a collection of operators that take tables as their operands and return a table as their results

8 relational algebra operators
 restrict
 project
 product
 join
 union
 intersect
 difference
 divide

topological relations: equals
same geometries

topological relations: disjoint
geometrics share common point

topological relations: intersects
geometrics intersect

topological relations: touches
geometrics intersect at a common boundary

topological relations: crosses
geometrics overlap

topological relations: within
geometry within

topological relations: contains
geometry completely contains

topological relations: overlaps
geometrics of same dimensions overlap

topological relations: relate
intersection bw interior, boundary, or exterior

What is spatial interpolation?
procedure of estimating the value of properties at unsampled sites within the area covered by existing known points

Inverse Distance Weighted
 the neighbourhood around the interpolated point is identified and a weighted average is taken of the observation values within this neighbourhood or range
 the greater the weighting coefficient, the less effect points will have if they are far from the unknown point

Proximity
all values are assumed to be equal to the nearest known point

BSplines
 is a piecewise polynomial method in order to provide a series of patches, resulting in a surface that has continuous first and second derivatives
 possible to be approximated by smoothing contours drawn through a TIN model

Kriging
 an optimal method of interpolation, for use in the mining industry
 basis is the rate at which the variance bw points changes over space

types of kriging
 simple (assuming the mean is constant)
 ordinary (assuming the mean is constant in the local neighbourhood)
 cokriging (will use information from one or more correlated secondary variables)
 indicator (kriging of indicator variables, represents membership in a set of categories)

Data sampling
 regular
 random
 transect
 stratified random
 cluster
 contour

Spatial Moving Average (SMA)
 one of the most common methods in GIS for raster and vector data
 based off of predicting the value of a specific area depending on the values of the neighbouring known points

Trend Surfaces
interpolation method based on the polynomial regression in order to fit a leastsquares surface to the known points

Buffering
 goal: identify an area within a certain distance from a given spatial entity
 ex. find the region that is within 300m from the pollution source

Digital Elevation Model (DEM)
refers to the elevation of the terrain (bare surface) above the datum

Digital Surface Model (DSM)
refers to the elevation of both the terrain and the landcover

spatial pattern analysis
understanding how information is distributed over one or several phenomenon

Agentbased model (ABM)
a class of computational models for simulating the actions and interactions of autonomous agents (both individual or collective entities such as organizations or groups) with a view to acsessing their effects on the system as a whole

