Final Flashcards
what is a network?
a system of interconnected lines and intersections, abstract representation of real world routes of people objects phenomenon etc
What is geocoding?
finding a geographic location from an address
In order to geocode we have to have
input dataset
output dataset
processing algorithm
reference dataset
What is an input dataset?
a list of addresses
What is an reference dataset?
a database of geospatial information, defines beginning and end number of each street
what is a processing algorithm
locates the input dataset
breaks the addresses into parts and then figures out where on the block it should be
What is an output dataset?
a set of poitns, geospatial information associated with the inout dataset
What are the network types?
transportation (undirected) and geometric utility (directed)
What are the components of a transportation network?
edges, junctions, barriers, turns
what are the components of a directed network?
Edges, sinks, source junction, barrier, point feature, area feature
List the steps in address geocoding
addresses are parsed into seperate components
each component is compared to the same field in the reference layer
candidates are scored based on closeness of matches
What score means the geocoding was a good match?
80-100
what are some problems with TIGER files?
Accuracy of location and correctness of address and location
What is an event layer?
The layer added from x y points
Types of transportation network datasets
optimum route shortest path, optimum route travelling salesman, closest facility, service area, location allocation modeling for a facility location, origin destination cost matrix,
Types of geometric utility datasets
flow direction, tracing edges and junctions upstream or downstream, artificial barrier
What are spatial operations
spatial functions, operations work on coordinate information and attribute data, solve a spatial problem
what are selection operations
similar to attribute queries, selection function work on spatial data, create layer from selection, use set algebra
What is boolean algebra
AND OR NOT
what are spatial selection operations
adjacency, containment, are identical to, intersect, are within a distance of
What are classification operations
reclassification or recoding, categorizes geographic operations on a set of conditions
What are overlay functions
data must be in common coordinate system, both spatial and attribute data may change, combines features at same location
What is a clip
boundary layer is cookie cutter, data layer is clipped, output has attributes of only the data layer
What is an intersect?
Combines data from both layers with only overlapping regions remaining, combines attributes of both layers
What is a union
includes all data from both inputs, including attributes
What is a problem with vector overlay
boundary issues
What happens with line-in-polygon?
only arcs found within th ebase layer polygons are included in the output
The attributes from the polygon are transferred to the arcs
What happens with an intersection?
uses geometric AND to compute the overlapping area, attributes from both polygon are transferred to the output, also called polygon on polygon
What happens with a union
uses geometric OR to compute the overlapping area
all input features from both layers remain
attribute values are assigned by containment
attribute inheritance, polygons only
What happens with a symmetrical difference
using XOR will output polygon areas that do not overlap
What happens with a clip
attributes from the clip layer are not transferred to the output
What are the 8 types of vector overlay
Dissolve append/merge union clip identity intersect update erase
What happens with a dissolve
removes boundaries between polygons or nodes between arcs, features with same attributes are dissolved
What happens with an identity
all featurs from first input layer persist
keeps its identity
attributes from both layers exist where there is overlap
order of inout and overlay matters
polygon on polygon, line, or point
what happens with an update
all features exist in output
the update coverage features replace the area they overlap in the input coverage
underlapping features from input are erased
attributes only from input layer exist in output
order of input and overlay matters
What happens with a clip
cookie cutter
only input layer features and attributes exist in output
polygon on polygon, line or point
what happens with an erase
cookie cutter, only input layer features and attributes exist in output, order of input and overlay matters, polygon on polygon, line, or point
What happens with a split
divides the first inout layer into a number of smaller layers based on the second input layer
the name of the output feature classes will be the same as the split fields unique values
What is a buffer?
A proximity function, a region that is less than or equal to a specified distance from a feature
What are the types of buffers
fixed buffers
dissolved buffers
compound buffers
nested buffers
what is cartography
the art and techniques of making maps
What are the map purposes
audience
info to communicate
area of interest
presentation medium
types of thematic maps
point symbol, area symbol, dot maps, proportional symbol, area class, flow line maps, choropleth maps, isoline, grid based map, cartograms
What are the visual variables in symbology and labeling
shape, hue, orientation, value, size, texture
how is color expressed?
as an RGB triplet, each component can vary from zero to 255 maximum value. 0 will be black and all 255 will be white
ArcMap can define color in what models?
RGB, CMYK, HSV, gray, names
A 2 class map can be suitable for
binary data or data with positive and negative values
4 to 8 classes in a map usually ensure that map readers can
see distincr patterns and can match color hue, lightness, and saturation on the map to the legend
More than 8 classes will produce
more complex patterns and map readers may not be able t match the used colors to the map legend
Classification should…
maximize the between class differences and minimize the within class differences
what are the five ways to classify raw data
unclassified natural breaks equal intervals quantiles unique scheme
What is the natural breaks classification
finds existing groups of values in the data and puts them together, using natural gaps in the data. It works well on unevenly distributed data
What is the equal interval classification
the class system takes the range of values in the field and divides them into a specified number of classes of equal size. very useful for ratio data
What is a quantiles classification
put about the same number of features in each class, this method creates a very balanced map with all classes equally well represented but some of the classes may be very close together in terms of their values
What are the concepts of raster data structures
grid often has its origin in the upper left corner, single values associated with each cell, rules needed to assign cell value to object that does not cover entire cell
what is raster data resolution
the minimum linear dimension of the smallest unit of geographic space for which data are recorded
What three fields are always present in the grid attribute table
the objectid, the value field, and a count field indicatinf how many cells contain that value
what is an artifact
an anomaly in the data
What are discrete rasters
essentially store features but in raster format, have relatively few values that change abruptly from one category to another
How can you display raster data
thematic rasters, image rasters
What is cell size
length or width of a cell on the ground
What is extent
area that a raster represents on the ground
Whats in a cell?
each cell can have zero, one, or multiple values, but no cell can be empty, values can be numeric or text
