midterm Flashcards
Describe why maps are essential for displaying geographic information.
spatial relationship between symbols to perform spatial operations.
What is an information system?
frame work that helps us Helps us organize, store and access, retrieve manipulate analyze what we know
Data
most mundane info (text symbols numbers)
information
broad or narrow definition = data without meaning
info exists independently ( without knower)
knowledge
entails a knower, has bias and requires assimilation
Knowledge is information when it is read and understood.
order of data info knowledge
data > information > knowledge
ease of sharing
knowledge ???
evidance ??
info ??
data ??
data = easy
info = easy
evidance = not easy
knowledge = difficult
wisdom = impossible
types of knowledge Codified
written down and transferred with ease
types of knowledge Tacit
Tacit - slow to acquire and difficult to transfer
What role does time play in spatial data?
4th dimension of spatial objects
Tracks changes over time.
Essential for understanding trends.
Creates time-series data.
Spatial Data
Information that has a geographical or locational component
Spatial vs Aspatial data
spatial is location-based information tied to geographic coordinates
VS
aspatial data lacks geographic coordinates and is not linked to specific locations
why is geographic information special?
Geographic information is special because it adds a location context to data, helping us understand spatial relationships and make informed decisions.
Define measurement and how it is used?
Measurement is the quantification of attributes of an object or event to compare and communicate.
Define the difference between extensive and representationalism, with respect to measurement
Extensiveness in measurement study refers to the degree to which a measurement comprehensively covers all relevant aspects of the concept being measured,
representationalism emphasizes the accuracy with which the measurement represents the underlying concept, even if it doesn’t encompass all its facets.
Continous fields
Continuous fields refer to geographic or spatial data that represent phenomena or attributes as a continuous distribution across an area, rather than as discrete points or features. These fields can vary smoothly over space, such as temperature or elevation across a landscape, and are typically modeled using mathematical functions.
Aspatial data
data entries that are not tied to a location on the earth’s surface
What is meant by geodesy ?
scientific discipline that deals with measuring and understanding the shape, size, and gravitational field of the Earth. It involves the precise measurement of the Earth’s surface
What is GIS?
“SYSTEM” implies a group of connected entities and activities
what is gis used for
measure aspects of geographic phenomena and processes
- represent these measurements, usually in the form of a computer database, to emphasize spatial
themes, entities, and relationships
- operate upon these representations to produce more measurements and to discover new
relationships by integrating disparate sources
- transform these representations to conform to other frameworks of entities and relationships
Ellipsoid
an ellipsoid refers to an oblate spheroid, which is a three-dimensional shape that closely approximates the Earth’s geoid
What is a DEM?
Digital elevation model describes continuous evaluation above sea level
DSM
digital surface model , includes elevation of all features in terrain like buildings
coordinate systems
DTM
digital terrain model , Contains only elevations of bare ground (no buildings)
Nominal Level (Categorical):
Data at this level are categorical and can be placed into distinct categories or groups.
- There is no inherent order or ranking among categories.
- Examples include colors, gender, and types of fruit.
- Only operations allowed are equality and inequality (e.g., “equal to” or “not equal to”).
Ordinal Level (Ordinal)
Data at this level can be categorized, and there is a clear order or ranking among the categories.
- However, the intervals between categories are not necessarily uniform or meaningful.
- Examples include educational levels (e.g., elementary, middle, high school) and customer satisfaction ratings (e.g., “very dissatisfied” to “very satisfied”).
- Operations include equality, inequality, and ranking (e.g., “greater than” or “less than”).
Interval Level (Interval):
- Data at this level have meaningful intervals between values, but there is no true, meaningful zero point.
- Arithmetic operations like addition and subtraction are meaningful, but multiplication and division are not.
- Examples include temperature measured in Celsius or Fahrenheit and calendar years (e.g., 2023, 2024).
- Operations include equality, inequality, ranking, addition, and subtraction.
Ratio Level (Ratio):
- Data at this level have meaningful intervals between values and a true, meaningful zero point.
- All arithmetic operations (addition, subtraction, multiplication, division) are meaningful and make sense.
- Examples include age, height, weight, and income.
- Operations include equality, inequality, ranking, addition, subtraction, multiplication, and division.
two types of coordinate system
cartesian and the latitude longitude
What is a geoid?
Shape of the earth if the oceans where to flow freely creating a global sea level
What is a developable surface?
Methods to project info found on a globe into geometric forms
Provide some examples of developable surfaces?
Planes
Cylinder
Cones
Tangent map projection
If globe touches devopable surface at a single point it is tangent
What is surface globe projection
If the globe intercepts with developable surface it is surface
3 classifications of map projections
Cylindrical, azimuthal (planar ) , conical
Mercator projection
Meridian lines and Parallel lines cross at 90* , angular relationships are maintained in this projection
Rhumb line
Line of consistent angular direction
Universal Transverse Mercator (UTM)
Coordinate system
60 zones, each 6* of longitude wide based on Cartesian coordinate system
Transverse Mercator
For maps of quadrant at scales from 1:24,000 to 1:250,000 . Used for mapping large areas that are mainly north - south in extent
GPS
Global Positioning System ; determines exact x y z location on earth
WHO DEVELOPED GNSS??
USA military , make public by R. Raegan
Shelf life of GPS satellites
Approximately 12 years
When was first satellite launched?
1989
What characteristics are usually lost in map projections?
Shape , area, angles, meridians topology
azimuthal map
An azimuthal map is a flat representation of the Earth’s surface with directions radiating from a central point.
What is an equidistant map?
An equidistant map accurately shows distances from a central point, but it distorts shapes and areas.
UTM strengths ?
The UTM projection is strong in accurately representing local areas and distances.
oblique Mercator
oblique Mercator provides an accurate representation of a specific area by using an oblique angle of projection
allowing it to focus on a region of interest with minimal distortion.
Benefits of azimuthal projection
Accurate at the center point for direction and distance.
Greatest distortion of azimuthal
Increases away from the central point.
Where is azimuthal distortion preserved ?
Distances and directions from the central point.
Benefits of conical projections
preserve both direction and area, making them suitable for mapping specific regions with minimal distortion.
What is a map projection?
Systematic transformation of 3D earth onto a 2D map
Albers Equal-Area Conic
prioritizes area accuracy
Lambert Conformal Conic
maintains shape accuracy.
Equidistant conic projection is used when the mapmaker wants to ?
maintain accurate distances from specific points or along specific lines on the map.
What is GNSS
“Global Navigation Satellite System.”
provide satellite-based navigation and location information.
What is Europe GNSS called
“Galileo.”
Provide three examples of modern uses for GPS.
Three modern uses of GPS include:
- Navigation
- Location-Based Services (geotagging photos etc)
- Precision Agriculture
Min number of satellites for full coverage of earth
24
Discrete objects
Discrete objects are separate and distinct entities
continuous fields
continuous fields represent smoothly varying data over an area.
Example of discrete object
A tree is an example of a discrete object. It’s a separate and distinct entity with clear boundaries.
Example of a continuous field:
Temperature distribution.
3 segments of GPS
And what they do.
Space> satellites orbiting earth
control> ground stations that monitor satellite
user> receivers used to determine position via satellite
