EAS 221 final

Card Set Information

EAS 221 final
2014-12-13 18:25:06
final exam
Show Answers:

  1. 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. 2 ways of thinking as GIS as a career:
    • 1. GIS professional (analyst, programmer, manager)
    • 2. GIS user (business manager, biologist, etc.)
  3. 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
  4. GIS
    the common ground between information processing and the many fields using spatial analysis techniques
  5. 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
  6. Why do we need georeferenceing?
    • navigation
    • emergency response
    • real estate
    • courier services
    • market analysis
    • distribution of clients, customers, etc
  7. Requirements for georeferencing?
    • uniqueness
    • interoperability (working together across organizational boundaries), persistence through time
  8. 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
  9. 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
  10. Orthometric heights
    height above sea level
  11. Geodetic longitude
    the angle bw the prime meridian and the meridian passing through the point
  12. Geodetic latitude
    the angle bw the equator plane and the normal to the ellipsoid passing through point
  13. Geodetic height
    the distance along the normal bw point 'p' and the ellipsoid
  14. 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
  15. 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
  16. Kinds of distortions from transitioning from 3D to 2D
    • area
    • shape
    • distance
    • direction
  17. Lambert Conformal Conic
    minimal distortion near standard parallels, areal scale is reduced between standard parallels and increased beyond them
  18. 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)
  19. Common raster formats
    GeoTIFF, JPEG2000, MrSID, GRID
  20. Digital Elevation Models, 3 possible sources?
    • 1. aerial photography
    • 2. topographic maps
    • 3. stereostopic
  21. 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)
  22. 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)
  23. 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)
  24. 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
  25. 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
  26. GPS Configuration
    • Space segment
    • control segment
    • user segment
  27. Space segment
    satellites provide navigation signal and relay orbital and clock data
  28. user segment
    user tracks satellite signals, downloads data, and computes position, velocity, and time
  29. control segment
    ground control tracks satellites and measures and uploads ephemeris and clock data
  30. Toolbox perspective
    an information technology which stores, analyzes, and displays both spatial and non-spatial data
  31. 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
  32. The organizational perspective
    A decision support system involving the integration of spatially referenced data in a problem solving environment
  33. the functional perspective
    a computer-based information system that deals with acquisition, management, manipulation, analysis, presentation, and dissemination of geospatially referenced data
  34. Evolution of GIS software
    • sub-routine libraries (60s/70s)
    • toolbox w/ CLI (command line interface) (70s/80s)
    • task-oriented system (graphical user interface) (90s/100s)
  35. the fundamental problem
    the more you zoom in, the more complex and dynamic it gets
  36. 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
  37. Solution to the fundamental problem: Modeling
    a data model in geographic information systems is a mathematical construct for representing geographic objects
  38. Data models
    • data in GIS represents a simplified view of the real world
    • defined as the relationships among objects in a spatial DB
  39. Attribute Data
    • used to record the non-spatial characteristics of an entity, aka items or variables 
    • help describe and define the features we wish to represent in a GIS
  40. 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
  41. Ordinal attributes
    • imply rank order or scale by values
    • may be descriptive such as small, medium, large, or may be numeric (classifications from 1-10)
  42. Interval/ratio attributes
    used for numeric items where both order and absolute difference
  43. Levels of GIS data modeling
    • reality
    • conceptual model
    • logical model
    • physical model
  44. conceptual models
    • field based (attributes can be thought as varying continuously from place to place)
    • object-based (features can be thought of as discrete entities/objects)
    • networks (object-based, but emphasis is on the interaction bw objects along pathways)
  45. 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)
  46. Data Compaction
    • approaches to reduce storage requirements 
    • - run length encoding
    • - block coding
    • - chain coding
  47. Data Quality
    • the totality of characteristics of a product that bear on its ability to satisfy a stated and implied need 
    • accuracy + precision = quality
  48. 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
  49. Data Quality Factors
    • scale
    • currency
    • lineage
    • documentation or metadata
    • standards
    • accuracy
    • precision or resolution
  50. Systematic error
    can be rectified if discovered, because its source is understood
  51. random error
    error in measurement caused by factors that vary from one measurement to another
  52. cross-validations
    uses all the data to estimate the trend and autocorrelation models, and to estimate how far the predicted information from actual measurements is?
  53. validations
    it uses few numbers of independent samples from the case study to estimate how perfect the estimated data is
  54. 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
  55. RDBMS: utilization of keys
    • relations bw tables (ie entities) are represented through the utilization of keys
    • super keys, candidate key, primary key, foreign key
  56. 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
  57. Relational Algebra
    a collection of operators that take tables as their operands and return a table as their results
  58. 8 relational algebra operators
    • restrict
    • project
    • product
    • join
    • union
    • intersect
    • difference
    • divide
  59. topological relations: equals
    same geometries
  60. topological relations: disjoint
    geometrics share common point
  61. topological relations: intersects
    geometrics intersect
  62. topological relations: touches
    geometrics intersect at a common boundary
  63. topological relations: crosses
    geometrics overlap
  64. topological relations: within
    geometry within
  65. topological relations: contains
    geometry completely contains
  66. topological relations: overlaps
    geometrics of same dimensions overlap
  67. topological relations: relate
    intersection bw interior, boundary, or exterior
  68. What is spatial interpolation?
    procedure of estimating the value of properties at unsampled sites within the area covered by existing known points
  69. 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
  70. Proximity
    all values are assumed to be equal to the nearest known point
  71. B-Splines
    • 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
  72. 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
  73. types of kriging
    • simple (assuming the mean is constant)
    • ordinary (assuming the mean is constant in the local neighbourhood)
    • co-kriging (will use information from one or more correlated secondary variables)
    • indicator (kriging of indicator variables, represents membership in a set of categories)
  74. Data sampling
    • regular
    • random
    • transect
    • stratified random
    • cluster
    • contour
  75. 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
  76. Trend Surfaces
    interpolation method based on the polynomial regression in order to fit a least-squares surface to the known points
  77. 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
  78. Digital Elevation Model (DEM)
    refers to the elevation of the terrain (bare surface) above the datum
  79. Digital Surface Model (DSM)
    refers to the elevation of both the terrain and the land-cover
  80. spatial pattern analysis
    understanding how information is distributed over one or several phenomenon
  81. Agent-based 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