1Which of the following GIS software is produced by the Environmental Science Research Institute?
ArcGIS
2The US National Spatial Data Infrastructure (NSDI) was initiated in
1994
3What is a Geographic Information System
GIS: a computer based system to aid in the collection, maintenance, storage, analysis, output, and distribution of geographic information
4GIS Era of Innovation
1960s to 70s
5First GIS
Canada GIS, 1963
6The Era of Commercialization
1980s to 90s
7ARC/INFO by ESRI (year)
1981
8Clinton Executive Order (year)
1994
9Clinton Executive Order created what agencies...
US NSDI, FGDC
10NSDI
National Spatial Data Infrastructure
11FGDC
Federal Geographic Data Committee
12GIS day
Wednesday of Geograohy Awareness Week in November
14Era of Exploitation
2000a
15Conceptual Representation
Data model
16Logical Representation
Data structure
17Physical Representation
Machine code
18Object based model: geographic space:
represented by a set of discrete and identifiable objects
19Object based model: an object has
identifiable boundaries
20Object based model: an object is describable by
one or more properties
21Field based model: geographic space
represented by a set of continuous fields
22Field based model: a field is described by
every possible position within the field
23Field based model: every possible position has
one or more properties
24A GIS data model is
the representation of real world phenomena in GIS
25A GIS data model includes
the model of geographic space (locations) and the model of properties (attributes)
26Two GIS models
vector and raster
27Vector model
object based conceptual representation
28Raster model
field based conceptual representation
29Field based model is like...
a grid
30Object based model is like...
points and lines and polygons
31Geometric primitives are
point, line, polygon
32Geometric primitives are for ___ models
vector
33A point is represented with
an x, y coordinate pair
34A point has
no size/no area
35A line is represented as
a sequence of ordered coordinate pairs
36A line can be
a straight line or a polyline
37A polyline is
ann ordered set of connected straight lines
39A polygon is represented as
a sequence of interconnected lines
40A polygon has the first and last ________
x, y coordinates being the same
42Vector data model: spaghetti model stores individual objects ________
separately as geometric primitives
43Spaghetti model: advantages
Easy to create, store, update, and delete an object
Used in computer mapping systems
44Spaghetti model: disadvantages
Not explicitly record connections of line segments when they cross or meet
Duplication: objects are stored twice and may not be the same (gaps or overlap)
Difficult to do analysis: which objects are adjacent, how are objects spatially related
45Vector data model: topological model
Topology: he study of geometric properties that do not change when teh forms are bent, stretched, or undergo similar transformation
46Spatial relations
disjoint, touch, overlap, within/contain
47Topological model
organizes and stores objects based on the concept of topology
48Most common topological model
Arc-Node
49Arc Node model
stores objects' geometric primitives and the topological relationships between the primitives. objects and their topological relationships can be constructed from the primitives
50Arc node: point data
node table is stored
51Arc node: line data
node table and arc table are stored
52Arc node: polygon data
node table, arc table, polygon table are stored
53Topological model: advantages
Enhanced spatial operations: adjacency, connectivity, network, etc
Supported by powerful database operations (SQL)
54Topological model: disadvantages
Slow to retrieve data from multiple tables
High quality data is needed
55Vector data model: object oriented model
A real world object is modeled as an object
56Object oriented model: each object has
a set of variables containing the data for the object
a set of messages to which the object responds
a set of methods as a body of code to implement a message
57Raster Data models are used
to represent continuous fields
58Raster data model defines the world as a
regular set of cells and properties are assocaiated with each cell location
59Raster cell size (resolution)
Trade-off between data voluem and position accuracy
60Feature
a feature is an object represented with vector data model
61Layer
A layer is a collection of objects of the same geometric type and usually of the same theme
62A real world phenomenon can be represented as (model)
A raster or a vector
63A real world phenomenon can be represented as a (geometric primitive)
point, line, polygon
64Representation is determined by factors such as
human perception, map scale, application needs
65Locations on the Earth's surface are measured within a ______________ and are described by ___________________ in the ___________
spatial framework, coordinates, framework
66A coordinate consists of a _______________________ that specify location in relation to an origin
pair of numbers
67The coordinates quantify the _________ from the origin along a standard ____________
distance, direction
68A _________________ is a system for specifying points using coordinates measured in some specified way
coordinate system
69The Earth's surfance is the __________ and __________ spatial framework to measure locations
primary, unique
70The corresponding coordinate system for this framework is called
geographic coordinate system
71The locations, latitude and longitude are called
geographic coordinates
72GEOID
earth's true shape
73Poles
the axis of revolution of the ellippsoid
74Equator
the circle mid way between two poles with a right angle to the polar axis
753 commonly used official ellipsoids
Clarke 1866, GRS80, WGS84
76Users for: Clarke 1866
North America
77Users for: GRS80
Worldwide
78Users for: WGS84
Worldwide
79Longitude and latitude
Conversion from degrees-minutes-seconds to decimal degrees
80Latitude measures the angle from the ______ to the _______
equatorial plane, earth's surface
81Longitude measures the angle from the ______ to the _______
prime meridian plane, north-south plane that interesects the location of interest
82The Equator is a
circle being perpendicular to the axis and passing the mass center
83The longitude of the point is the
rotation angle
84Meridian
curve of constant longitude
85Parallel
curve of constant latitude
86Equator is taken as
0 degrees latitude
87Geographic coordinate system
origin, latitude and longitude, curve surface
88Elevation is measured as the
disstance from a location to the mean sea level
89Spatial data in a GIS most often uses a
Cartesian coordinate system
90Cartesian coordinates are recorded as
(x,y)
91Cartesian coordinate system has
2 or 3 orthogonal axes on a plane surface
92Cartesian coordinate systems make it
easy to measure distance and direction
93Map projection
a process that defines how positions on the Earth's curved surface are transformed onto a flat surface
94Why do we need to do projection?
Earth is curved but it is much eaiser to measure distance on a plane
95Class
the shape of the developable surface
96Case
whether the developable surface touches or cuts through the globe, tangent or secant
97Tangent
the developable surface touches but does not slice through the globe
98Secant
the developable surface slices through the globe
99Aspect
how the developable surface is placed relative to the globe