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GIS I - GROUP A++!!!!!!!!! (Scale of Measurement (Interval (Quantitative…
GIS I - GROUP A++!!!!!!!!!
Data Types
Raster Data Model
Comprised of grids or pixels
Best for continuous data
Ex: Aerial Photos, elevation etc...
Data struture
JPEG
Mosaic dataset
TIFF
Types of Raster Data
Thematic Data
Measured quantity of a particular phenomenon
EX. Topography
Image Data
Visual representation that requires classification/interpretation.
EX. Google earth
Raster Cell Values
Discrete or Categorical data
(represented with integer cell values)
Continuous data
(represented with Floating point cell values)
Raster Data Compression
Run-Length Encoding
Grouping of cell values
Quad Trees
Cells of hierarchical quadrants
Raster Data Problems
Mixed Pixel
Large Areas of Missing Data
Vector to Raster Exchange
Original vector on top of raster
Vector converted to raster
Raster converted back to vector
Comparison of the original vector with the reconverted vector.
Data Storage
Binary
0's and 1's
Byte
256 Values
ASCII
127 Defined Codes
Two Byte Unsigned
0 to 65,535
ANSI
256 Total Defined Codes, Includes ASCII's 127 Codes
Vector Data Model
Comprised of Nodes, Polylines, Polygons
Ex: Shape files
Best for discrete boundaries, such as country borders, land parcels, and streets
Data structure
CAD
Geodatabase feature class
Shape file
TIN (Triangular Irregular Network)
GIS
GIS as an analysis tool can specify where, what it is, where its occupied, how it relates to other pieces of data
Process of GIS
(1) Identity geographic problem or issue
(2) Ask questions about it
(3) Use data to make a map
(4) Explore the patterns that appear
(5) Enhance the data or modify the analysis
(6) Ask a new question or develop a solution to the problem
(7) Repeat
Scale of Measurement
Ordinal
Categorical data with a natural ranking or order
Categorical Data
Interval
Quantitative or Numerical data on a physical scale
Zero does not represent an absence
Dates, Times, Temperature (F, C)
Nominal
Naming, Non-numerical Values
Types or Class of data
No rank or hierarchy
Ratio
Quantitative data- ratios between two values
have a definite meaning
Meaningful zero
Density, Population, Ethnicity, Percent value, Temperature (K)
Feature Data Structures
Object-oriented
Feature-relational
ArcGIS Geodatabase
Spatial Entities are defined as objects
Geometry is stored in BLOBs
Georelational
Geometry and attributes are held in different files.
Topological
ArcInfo Coverages
Holds geometry and topology together in data structure as nodes (points), arcs (lines) and polygons
Spatial relationships and spatial integrity maintained
Non-topological
ArcView Shapefiles
Holds geometry and topology separately in different files
Doesn't keep spatial relationships of features
Validation Rules
Relationship Rules
Topology
Rules about spatial relationships
Connectivity Rules
Geometric networks
Model common networks and infrastructure of resource flows
Ex: Water distribution,electrical lines, gas pipeline, etc.
Custom Rules
Attribute Domains
Constrain values allowed in any particular attribute for a table or feature class
Types
Short
Double- Double precision floating
Float- Single Precision
Text- Alpha numeric
Long
Date- Date and time data
GIS Programs
ArcInfo
ARCGIS
ArcCatalog
ArcMap
Attribute Tables
Relational Operations
Intersect
Combines fields/attributes in common
ArcView
Diffrence
Combination of fields not in common
Union
Combination of all fields
Join
Referencing and Map Projection
Datums
NAD 27
Clark Ellipsoid 1866, based in the U.S
WGS 84
Datum used for global positioning system (GPS)
International Standard used.
NAD 83
Earth center datum, U.S. only
Still used today when mapping the United States
Projections
Planar
Azimuthal Equidistant
Conic
Lambert conformal
Cylindrical
Mercator conformal
Preserve
Area
Shape
Distance
Direction
Distortion
Conformal Property
Shapes are preserved
Equivalent Property
Area is preserved
Case
Secant Case
Two lines of tangency
Simple Case
One line of tangency
Perspective
Gnomonic- Light source at the center
Gnomonic projection- viewed from the center of the Earth
Stereoscopic- Light source at antipode
Stereoscopic Projection- viewed pole to pole
Orthoscopic- Light source infinitely far away
Orthoscopic Projection- viewed from an infinite point in space
Grid Coordinate System
X-direction
Easting - positive - Most of gride system using only this part
Y-direction
Nothing
Aspect of a map projection (based on axes parallel )
Transverse
90 degrees to it
Oblique
Any other angle
Equational
Earh's rotation axis
Projected Coordinate System for the United States
State Plane Coordinate System (SPCS)
Zone to minimize distortion of states,
East-West: Lambert Confomal
North-South: UTM Projection
Better for local accurate database.
UTM
Initially military standard, 120 total zones, Transverse Mercator distortion increases as you get further from equator, Measures from 84N-80S
Georeferencing
Purposes
Post codes
Destination for mail
Hierarchy is used to organize
Fails for rural areas
Placenames
Earliest form of georefrencing
Works for different scales (local, city wise)
PLSS for Cadastre
Record of property ownership
Unique to Western U.S.
georeferencing methods
Unique
shared
persistent through time
Digital Data
Analog maps through digitizing or scanning
Must be transformed to use in GIS
Remotely Sensed Data
From GPS
Existing sources via internet
Amazing group memebers!!!!
:
Applications
GNSS (Global Navigation Satellite System)
Satellite Segment
Control Segment
User Segment
