NR 509 Exam Test Questions and Answers
GPS
Answer: Global positioning system
NAVSTAR GPS
Answer: US-Navigation Satellite Timing and Ranging-consists of 3 segments-space (satellites), control
(control station-collect satellite broadcasts), user (receiver, processors, antennas). 24 satellites,
managed by U.S. air force, used SA until 2000
Selective Availability
Answer: government corrupted signal for security- from 1990 until 2000, caused errors of 50 to 100 m -
with SA off only get errors of about 5 m
Sources of Error in GPS data
Answer: Ephemeris data- errors in the transmitted location of the satellite, satellite clock, atmospheric
disturbances, multipath-errors caused by reflected signals, receiver errors. ie in cities, mountains,
forests, the signal can bounce off buildings and you don't have as much of a view of the sky-access to
fewer satellites
Differential Correction
Answer: Collect raw data at your position with handheld GPS (contains errors mentioned above), collect
data off of a base station (surveyed, accurate location), log with base station, bring both datasets
together and calculate the true location, get base station from CORS network (continuously operating
reference station)
WAAS
Answer: Wide area augmentation system-real time differential correction for airplanes
Creating a GIS dataset from scratch
Answer: 1.Map prep: choose projection/coordinate system. decide on data source:orthophoto, scanned
map, etc. decide if raster or vector, organize info into themes (coastline, oyster reef, nesting sites, etc).
2.Coding scheme
Digitizing the map: manually-not used much anymore-tedious but good. Scanning- expensive , fast, need
to edit product a lot and have to code data . Heads up digitizing- most popular-use mouse to digitize on
screen.
3.Attribute entry.
4.Proofing- rules about linework and topology
5. metadata-most important info- all the necessary info- date, who made it, coordinate system etc- STDs
you have to follow
Spatial analysis on single layers of vector data: examples
Answer: where are farmlands? What wetlands are inside aquifers? Who abutts the bio reserve? Where
are wet soils? <-- data generalization. Take soils data from the whole state and cut out all but one town
= CLIP
Proximity analysis/neighbor analysis: what is within 100 ft of a public water supply well
, Overlay procedures
Answer: data analysis on multiple layers of vector data
ex: which wetlands are inside an aquifer, what watershed is that stream in?
poly/poly, line/poly, point/poly
command is UNION
Network Analysis
Answer: analysis on multiple layers of vector data
ie what is the fastest way to get from here to there? if you're putting in a domino's pizza, school bus,
garbage pick up, ambulance. lots of extra info in road data- 2 way or 1 way street, speed limit, daily
traffic patterns, etc.
Data Analysis on Raster Data
Answer: Neighborhood functions: arithmetic operations on focal pixel based on surrounding pixels-ie
calculate mean of all neighboring pixels within a 5 pixel radius for elevation- gets rid of detail- raster
smoothing- good for a contour map
Grid math- equivalent to vector overlay
hydrologic modeling- flow paths using elevation by pixel- can delineate watersheds and find out where
water will go
Terrain Modeling
Answer: ex- how does slope change across my study area? Where are north facing hillsides?
Mapping different aspects of the earth's surface based on elevation
examples- elevation, slope (for development), hillshade (shaded relief map, shows where sun hits),
contour maps, aspect (what direction is part of the earth's surface facing- wind, solar panels (face
south), kski resort), viewshed (identify a location and indicate everything i can see from that vantage
point-driven by what's in the shadow of a hillside-ski resorts-don't want to see them in the summer, cell
towers, fire fighters looking for forest fires, wind turbines), 3D (clouds, schools of fish, geology-bedrock,
groundwater thickness), cross section (elevation across a hiking trail)
Interpolation-idea behind it
Answer: how do i create a continuous surface of values from a sample of points at various locations.
Raster surface of large area that shows variation in whatever we are measuring- take point
measurments-interpolate raster surface-create derivative maps-geologist asking where to drop an oil
well
Inverse Distance Weighting
Answer: interpolation method
IDW
good for sudden changes, quick and dirty
based on Tobler's law- things that are closer together tend to be more similar, things that are farther
away tend to be more different- give more weight to things that are closer
GPS
Answer: Global positioning system
NAVSTAR GPS
Answer: US-Navigation Satellite Timing and Ranging-consists of 3 segments-space (satellites), control
(control station-collect satellite broadcasts), user (receiver, processors, antennas). 24 satellites,
managed by U.S. air force, used SA until 2000
Selective Availability
Answer: government corrupted signal for security- from 1990 until 2000, caused errors of 50 to 100 m -
with SA off only get errors of about 5 m
Sources of Error in GPS data
Answer: Ephemeris data- errors in the transmitted location of the satellite, satellite clock, atmospheric
disturbances, multipath-errors caused by reflected signals, receiver errors. ie in cities, mountains,
forests, the signal can bounce off buildings and you don't have as much of a view of the sky-access to
fewer satellites
Differential Correction
Answer: Collect raw data at your position with handheld GPS (contains errors mentioned above), collect
data off of a base station (surveyed, accurate location), log with base station, bring both datasets
together and calculate the true location, get base station from CORS network (continuously operating
reference station)
WAAS
Answer: Wide area augmentation system-real time differential correction for airplanes
Creating a GIS dataset from scratch
Answer: 1.Map prep: choose projection/coordinate system. decide on data source:orthophoto, scanned
map, etc. decide if raster or vector, organize info into themes (coastline, oyster reef, nesting sites, etc).
2.Coding scheme
Digitizing the map: manually-not used much anymore-tedious but good. Scanning- expensive , fast, need
to edit product a lot and have to code data . Heads up digitizing- most popular-use mouse to digitize on
screen.
3.Attribute entry.
4.Proofing- rules about linework and topology
5. metadata-most important info- all the necessary info- date, who made it, coordinate system etc- STDs
you have to follow
Spatial analysis on single layers of vector data: examples
Answer: where are farmlands? What wetlands are inside aquifers? Who abutts the bio reserve? Where
are wet soils? <-- data generalization. Take soils data from the whole state and cut out all but one town
= CLIP
Proximity analysis/neighbor analysis: what is within 100 ft of a public water supply well
, Overlay procedures
Answer: data analysis on multiple layers of vector data
ex: which wetlands are inside an aquifer, what watershed is that stream in?
poly/poly, line/poly, point/poly
command is UNION
Network Analysis
Answer: analysis on multiple layers of vector data
ie what is the fastest way to get from here to there? if you're putting in a domino's pizza, school bus,
garbage pick up, ambulance. lots of extra info in road data- 2 way or 1 way street, speed limit, daily
traffic patterns, etc.
Data Analysis on Raster Data
Answer: Neighborhood functions: arithmetic operations on focal pixel based on surrounding pixels-ie
calculate mean of all neighboring pixels within a 5 pixel radius for elevation- gets rid of detail- raster
smoothing- good for a contour map
Grid math- equivalent to vector overlay
hydrologic modeling- flow paths using elevation by pixel- can delineate watersheds and find out where
water will go
Terrain Modeling
Answer: ex- how does slope change across my study area? Where are north facing hillsides?
Mapping different aspects of the earth's surface based on elevation
examples- elevation, slope (for development), hillshade (shaded relief map, shows where sun hits),
contour maps, aspect (what direction is part of the earth's surface facing- wind, solar panels (face
south), kski resort), viewshed (identify a location and indicate everything i can see from that vantage
point-driven by what's in the shadow of a hillside-ski resorts-don't want to see them in the summer, cell
towers, fire fighters looking for forest fires, wind turbines), 3D (clouds, schools of fish, geology-bedrock,
groundwater thickness), cross section (elevation across a hiking trail)
Interpolation-idea behind it
Answer: how do i create a continuous surface of values from a sample of points at various locations.
Raster surface of large area that shows variation in whatever we are measuring- take point
measurments-interpolate raster surface-create derivative maps-geologist asking where to drop an oil
well
Inverse Distance Weighting
Answer: interpolation method
IDW
good for sudden changes, quick and dirty
based on Tobler's law- things that are closer together tend to be more similar, things that are farther
away tend to be more different- give more weight to things that are closer
