University of Pittsburgh GIS Exam-
Graded A
What is a GIS? - ANSWER-The person, the data, the computer.
Lets us visualize, question, analyze, and interpret data to understand relationships,
patterns, and trends.
3 functions of GIS - ANSWER-input, manipulation, output
input - ANSWER-import data from multiple sources (like spreadsheets, satellite
imagery, etc)
pros and cons of geodatabase feature classes - ANSWER-pros: easy access to all
relevant data, more specific classifications of data, generally more intuitive
cons: increased size impedes performance
Geodatabase - ANSWER-container for attribute tables, feature classes, rasters, etc
map document - ANSWER--container for and visualizer of layers, but does not contain
the raw data itself.
-one layer is one version of your source data, and does not necessarily reference an
entire data set (user chooses what is displayed)
-accessible from windows explorer (like a word doc)
types of GIS queries - ANSWER-attribute, location
editing - ANSWER-altering spatial or attribute data permanently
NOT changing symbology or how a feature class is represented
map layer and data source - ANSWER-a map layer is not a source of data, but it
provides a path back to the source
GPS - ANSWER-global positioning system
Navstar GPS - ANSWER-US Department of Defense developed
LA Air Force operated
1993-1995
GNSS - ANSWER-Global Navigation Satellite System - includes all nationalities' GPS
systems
, GPS purpose - ANSWER-direct weapons, unified navigation for the navy
GPS use - ANSWER-civilian access allowed with selective ability until Clinton shut it
down
selective availability - ANSWER-government allowed access to less accurate, degraded
signal
Wide Area Augmentation System (WAAS) - ANSWER-ground-based receivers detect
satellite positioning variations, which are then relayed to geosynchronous satellites so
that data can be corrected
WAAS purpose - ANSWER-increase accuracy in air traffic control
Continuously Operating Reference Stations (CORS) - ANSWER-privately-maintained
ground stations, data processed by National Geodetic Survey and NOAA. similar to
WAAS
GPS constellation - ANSWER-6 orbital planes, 4 satellites per plane, 31 operational
satellites
GPS constellation orbit altitude - ANSWER-median ~20,000 km
GPS constellation Air Force goal - ANSWER-have 24 GPS satellites online 95% of the
time
how GPS determines your position - ANSWER-satellites constantly sending signals,
receiver calculates time since signal left satellites, then triangulates based on at least 3
satellite signals
sources of GPS error - ANSWER-general relativity, spatial relativity, atmosphere,
receiver error, satellite malfunctions, multipath error, Positional Dilution of Precision
general relativity - ANSWER-satellite moving much faster than the receiver - satellite
has a slower clock
spatial relativity - ANSWER-gravity's effect on signal transmission - satellite has a faster
clock
multipath error - ANSWER-signal bounces off ground to antennae, adds extra time
atmospheric error - ANSWER-ionosphere, troposphere have different indexes of
refraction
Graded A
What is a GIS? - ANSWER-The person, the data, the computer.
Lets us visualize, question, analyze, and interpret data to understand relationships,
patterns, and trends.
3 functions of GIS - ANSWER-input, manipulation, output
input - ANSWER-import data from multiple sources (like spreadsheets, satellite
imagery, etc)
pros and cons of geodatabase feature classes - ANSWER-pros: easy access to all
relevant data, more specific classifications of data, generally more intuitive
cons: increased size impedes performance
Geodatabase - ANSWER-container for attribute tables, feature classes, rasters, etc
map document - ANSWER--container for and visualizer of layers, but does not contain
the raw data itself.
-one layer is one version of your source data, and does not necessarily reference an
entire data set (user chooses what is displayed)
-accessible from windows explorer (like a word doc)
types of GIS queries - ANSWER-attribute, location
editing - ANSWER-altering spatial or attribute data permanently
NOT changing symbology or how a feature class is represented
map layer and data source - ANSWER-a map layer is not a source of data, but it
provides a path back to the source
GPS - ANSWER-global positioning system
Navstar GPS - ANSWER-US Department of Defense developed
LA Air Force operated
1993-1995
GNSS - ANSWER-Global Navigation Satellite System - includes all nationalities' GPS
systems
, GPS purpose - ANSWER-direct weapons, unified navigation for the navy
GPS use - ANSWER-civilian access allowed with selective ability until Clinton shut it
down
selective availability - ANSWER-government allowed access to less accurate, degraded
signal
Wide Area Augmentation System (WAAS) - ANSWER-ground-based receivers detect
satellite positioning variations, which are then relayed to geosynchronous satellites so
that data can be corrected
WAAS purpose - ANSWER-increase accuracy in air traffic control
Continuously Operating Reference Stations (CORS) - ANSWER-privately-maintained
ground stations, data processed by National Geodetic Survey and NOAA. similar to
WAAS
GPS constellation - ANSWER-6 orbital planes, 4 satellites per plane, 31 operational
satellites
GPS constellation orbit altitude - ANSWER-median ~20,000 km
GPS constellation Air Force goal - ANSWER-have 24 GPS satellites online 95% of the
time
how GPS determines your position - ANSWER-satellites constantly sending signals,
receiver calculates time since signal left satellites, then triangulates based on at least 3
satellite signals
sources of GPS error - ANSWER-general relativity, spatial relativity, atmosphere,
receiver error, satellite malfunctions, multipath error, Positional Dilution of Precision
general relativity - ANSWER-satellite moving much faster than the receiver - satellite
has a slower clock
spatial relativity - ANSWER-gravity's effect on signal transmission - satellite has a faster
clock
multipath error - ANSWER-signal bounces off ground to antennae, adds extra time
atmospheric error - ANSWER-ionosphere, troposphere have different indexes of
refraction
