GIS Exam Flashcards
Where is the buffer created?
around points, lines, polygons and areas
What tool do you use to create a buffer?
Pairwise buffer tool
What is an example of a place you would analyze using a buffer tool?
Neighborhoods or schools in Toronto
What is a Query?
finding answers to questions using the table and extracting spatial features from a feature class (layer)
What are the 3 different types of queries?
- interactive
- attribute
- spatial
What is an interactive query?
select spatial features using the select tool or select spatial features or records from the table (shape field or not)
What is an attribute query?
- it is applied to an attribute table, conditions are specified by the user, and records meeting those conditions are selected using a SQL expression
- conditions are either true or false
What is the extraction tool? and what is it used for?
What is the overlay tool? and what is it used for?
what is a spatial join? and what is it used for?
What is the aggregation tool? and what is it used for?
How are data represented in GIS?
(this is on the exam)
objects, fields, and data models
What are 2 data models?
vector: objects and raster: fields
What are the 3 types of objects?
points, lines and areas (polygon)
what are objects?
well-defined boundaries in otherwise empty space
what are 3 things to know about fields?
- continuously change across space
- continuous surface
- variables change in value at all locations
what information is stored on an attribute table regarding the feature class?
the shape field will have the geometry
What does a standalone table store?
It stores any tabular data, not associated with spatial data
what are the 2 field properties?
alias and data type
What is an Alias?
it is a description
What is a data type?
fields
What data type is associated with the Nominal attribute level?
Text, Integer (Short, Long)
What data type is associated with the Ordinal attribute level?
Integer (Short, Long)
What data type is associated with the Interval attribute level?
Float, Double
What data type is associated with the Ratio attribute level?
Float, Double
What do you need to know about naming geodatabases? (4)
- name fields using only letters and numbers
- fields can’t have spaces (use underscore)
- alias can be used for description
- name must be unique to that table
Rational model or relational databased #1 (3)
- has multiple tables that will merge together
- column (field): reps attribute
- row attribute values an object: called a tuple
Relational Model #2 (3)
- each data set has a primary key ID at the end
- Foreign key: can be joined to primary key of other table
- relational join (attribute join)
What is an example of a one-to-one join?
- provinces to capitals
- principals to schools
what is an example of a one-to-many join?
- provinces to cities
-school boards to schools
what is an example of a many-to-one join?
- cities to provinces
- schools to school boards
What is an example of a many-to-many join?
- students to classes (50 stduents with 5 classes each)
- stores to customers
what is topology? (3)
- it creates data that is aware of its data and attributes
- flags errors
- intelligent data
What is containment?
a feature within another feature
what is an intersection?
overlap intersects or overlaps another layer
what is connectivity?
wheater a linear feature is connected to another linear feature
what is vector encoding?
- empty feature class: lines and points
- points lines and polygons are each encoded separately
what is spaghetti data also known as?
dumb data
what takes up more data topological data or spaghetti data?
spaghetti data
what was the first thing developed to store vector data? what year was it developed?
ArcInfo (1980)
how was vector data typically stored?
geography in one file and attributes in another file
What vector data storage was developed in 1993?
ArcView
Why was ArcView created?
simple format
changed vector format
universal format
non-topological
Where is raster data held?
one value is held in each of these squares
how many attributes can you have per layer for raster representation?
1 attribute per layer
what are examples of raster representation?
elevation, temperature, and soil acidity
how do the size and area of raster data squares relate?
the size and area are the same for each square
What types of digitalization is raster data?
jpeg, gif, camera, tv
what is real-world to raster?
the areal photograph is georefrenced
how is the location in a raster stored?
- not stored in x and y coordinates
- a cell has an implied location
how do we determine the precision of the location?
based on the cell size
does the level of resolution influence the goodness of the representation?
the higher the level the better, but that’s not always true. need to check variability captured by the ground sampling distance (GSD)
What are two types of data collection?
data transfer and data capture
What are the two types of data capture?
primary and secondary
What is primary data capture for raster data?
remote sensing, aerial photogrpahy
what is primary data capture for vector data?
surveying, GPS, Mobile GIS and VGI
What is secondary data capture for raster data?
scanning maps
what is secondary data capture for vector data?
digitizing
What does snapping do?
it automatically connects features
what are the three types of snapping?
end snapping, edge snapping, vertex snapping
what 3 rules do you follow when choosing what to input?
- digitize what you really need
- use level if accuracy according to task
input data as separate themes
what are the 2 common digitizing errors?
overshoot and undershoot
What is GPS?
NAVSTAR- Navigation system with time and ranging
how many satellites are available 95% of the time?
24
how many satellites are visible?
7
what does the control segment of GPS consist of?
- master control center
- 12 command and control antennas
- 16 monitoring stations
what is surveying?
- locations if objects determined by angel and distance measurements from known locations
- uses expensive field equipment and crews
- most accurate method for large-scale, small areas
what are the 4 global navigation satellite systems?
- GPS (NAVSTAR)- US
- GLONASS- Soviet Union
- GALLILEO- EU
- BeiDou- China
how does the GPS constellation vary?
- health of satellites
- orbits change daily
how is the Dilution of precision (DOP) examined?
- relative geometry of satellites
- multiplier of GPS errors
what do the 3 Dilution of precision (DOP or PDOP) ratings mean?
1- ideal
5- OK
10- Poor
where are signal blockages most common?
valleys and depressions
what can cause signal interference?
electronic noise and microwave antennas
What can cause signal obstructions?
dense canopy and urban canyons
What is a GPS user segment?
- GPS receivers
- signals received from GPS satellites are used to determine the user’s position and time
- civilian and military user’s
what are examples of GPS Receivers?
Phones, some watches, MTK D, Navigation devices (GPS), ipads, GPS system 500, etc.
what is volunteered geographic information (VGI)?
it is when citizens volunteer to contribute geographic data
what two apps are available in the ArcGIS platform for mobile GIS?
FeildMaps and Survey123
what is a spatial join?
joins attributes from spatial features in one layer to spatial features in another layer based on a spatial relationship between the two layers
what is aggregation?
process of grouping spatial features at a level of detail or resolution that is coarser than the level at which the features were created
what does the dissolve tool do?
it aggregates spatial features based on specified attributes
- need a dissolve field
- summarize numeric fields
- output new feature class
what is a boolean raster?
assigning a new value to each value of the input layer with the purpose of developing a Boolean (0,1) raster for use in subsequent analyses
what is a classification reduction?
assigns new values to classes or ranges of old values with the purpose of reducing the number of classes in the original input layer or to create a new classification scheme
What is a local function?
reclassification and overlay
What is reclassification?
creates a new raster layer by changing the attribute values of the cells of the input layer
What are the 3 types of reclassification?
- boolean raster
- classification reduction
- changing measurement scales
What is an overlay tool?
Boolean (AND, OR, XOR, OR)
What is a topological overlay?
spatial features combined to from new features (lines and polygons), attributes combined
a powerful overlay technique because popular by _____ in the year ____.
Ian McHarg’s
1960s
what is the union overlay operation?
union: overlays two or more polygon layers and keeps all areas in all layers
What is a symmetrical Difference overlay operation?
overlays an input layer with an updated layer and keeps only those portions that do not overlap
What is the intersect overlay operation?
overlays two or more input layers and keeps only those portions overlapping in all layers
what is the apportion polygon overlay operation?
overlays an input polygon layer with a target polygon layer
what is the identity overlay operator for?
overlays an input layer with an identity layer and adds attributes of the identity layer to the input layer
what is a neighborhood function?
functions that create an output layer in which the value of each cell is a function of the cells neighbouring the cell at the same location on the input layer
what are two types of neighborhood functions?
Focal functions and block functions
how to calculate the angle of a slope?
a= tan-1 (vd/ hd)
a- angle
hd- horizontal distance (units)
vd- vertical distance (units)
what are zonal functions?
they create an output layer by identifying cells that intersect with or fall within each zone on the input layer
what are zonal statistics?
- zones defined by a raster or feature layer (zone field)
- value raster
- calculate summary stats of values per zone
what are distance functions?
used to measure the distance from cells designated as source cells
what 4 questions do distance functions address?
- proximity
- straight line distance
- cost-weighted distance
- shortest path
What are global functions?
computes an output raster dataset in which the output value at each cell location is potentially a function of all the cells combined from the various raster datasets
what is a buffer?
a zone around a spatial feature to a specified distance
what is a buffer used for?
used primarily for neighbourhood analysis that aims to evaluate characteristics of an area surrounding a specific feature
what are examples of buffer usage?
- properties within a certain distance of a road
- looking for gaps in coverage
- delineation of areas around rivers and streams that cannot be developed
what are 5 buffer options?
- some (selected) vs all spatial features
- fixed variable width (field) buffers
- single or multiple buffers
- polygons, buffers can be outside or inside boundaries
- individual buffers vs dissolved buffers
what is the erase tool used for?
creates a new layer (feature class) that keeps features that fall outside the erased layer and removes those within
what is the clip tool used for?
creates a new layer (feature class) that includes only those features of the input layer that fall within the spatial extent of the clip layer
geography is represented as either _____ or _____
objects or fields
what is an object?
it is a well defined boundaries in otherwise empty space, it is countable (discrete)
what are the three types of objects?
points, lines, and areas
what is the vector representation used for?
vector data model is used to represent objects
how is spaced defined for vector representation?
space is defined by continuous XY coordinate space
what is topology?
it is the procedure for defining spatial relationships among features. (features know where they are and what is around them)
what are the 4 types of topological spatial relationships?
- containment
- adjacency
- intersection/ overlap
- connectivity
what are lines?
an ordered set of coordinates defines a line and each line is made up of potentially multiple line segments defined by two points
what are endpoints of an arc called?
nodes
what are angle points called?
vertices
______ is the arc not the line segment
feature
_____ arcs meet at nodes
two
what are the 4 categories of cell values?
- image raster
- thematic rasters
- interpolated rasters
- derivatives of each of the above
what is an image raster?
values rep measurements of energy captured by sensor
what is a thematic raster?
values represent a theme, category or class, usually are integers
what are interpolated rasters?
values represent a theme, category, or class, usually are integers
what are the types of raster cell values?
slope, classification, zonal statistics
how to increase the resolution in a a raster?
decrease the GSD not only the cell size
