CP 4510 GIS Exam
Summary Statistics tool
- Calculates statistics from table attributes - the user chooses fields and statistics types - Creates a new table as its output
Two types of raster formats than can be analyzed in arcgis pro
.img and .tiff
Types of Projections
1. Cylindrical (preserve direction and shape) 2. Conic (preserve area and/or distance) 3. Azimuthal or planar (preserve area and/or distance)
Ways to classify numeric data
1. Natural Breaks 2. Equal Interval 3. Standard Deviation 4. Quantiles 5. Geometric Intervals
Types of Thematic Maps
1. Unique value 2. Graduated Colors (polygons) 3. Graduated Symbol (Points) 4. Dot Density 5. Chart Maps
4 differences in Vector vs. Raster Model
1. Vector is discrete/categorical data while Raster is continuous data 2. Vector is integer values while Raster is floats or ints. 3. Vector has only value per category and Raster has large range in values. 4. With raster it is unlikely to have same values as adjacent cells
all map projections have one or more of these 4 distortions
1. direction 2. shape 3. area 4. distance
Ellipsoids
Actual shape of the earth. smooth shape with slightly smaller n/s axis.
Geographic (unprojected) Coordinate System
Based on spherical coordinates. Measured in degrees of lat and long
works like a cookie cutter to extract features that lie inside the boundary of another data set.
Clip
Merging
Combines all features from 2 or more data sets into single feature class.
Projected Coordinate System
Converts spherical coordinates to planar coordinates. Uses set of mathematical equations and projects 3d coordinates to 2d map.
DEM acronym
Digital Elevation Model
Projections all distort one or more properties of: ____, ____, _____, and ______.
Direction, shape, area, and distance.
Discrete vs Continuous Map Data
Discrete: objects exist in defined location (Point, lines, polygons) Continuous: Data exist everywhere (raster)
Defined or Equal Interval
Equal Sized classes. User chooses class range for defined interval map or number of classes for equal interval map.
Works like a cookie cutter to extract features that lie outside the boundary
Erase
Buffers are temporary delineations of an area within a specified distance of a set of features. They do not result in the creation of a new layer.
False
Spatial queries can select partial features (E.g the portion of a river that falls inside a given county)
False
T/F: Streaming data or GIS web services are datasets stored on your local computer
False
T/F: Tabular Joins are permanent
False
T/F: The vector model is best for continuous data. The raster model is best for discrete data.
False
T/F: UTM coordinate system breaks the world up into 6 zones of 60 degrees each
False, 60 zones of 6 degrees each.
A geoid shifts the ellipsoid relative to the datum to achieve a best fit between the two.
False, A datum shifts the ellipsoid relative to the geoid to achieve a best fit between the two.
T/F: data or numeric classification applies only to vector data
False, applies to vector and raster.
T/F: In a many to one join, one record in the target or destination table matches many records in the join or source table.
False, one record in join table matches many records in target or destination
T/F: there are 5 basic field types for a table.
False, there are 6.
T/F: The raster model stores features as map objects called points, lines, and polygons.
False, this is the vector model. Raster model breaks map area into small cells calls pixels.
a _______ is a homogenous collection of features with a common spatial representation and set of attributes stored in a database table. for example a line ______ representing road centerlines.
Feature class, feature class
Categorical Data
Features belong to categories (rock type, volcano type, etc.). Portrayed with unique values map, and categories can be numeric or text.
Natural Breaks
Jenks Optimization method and exploits natural gaps in data. Good for skewed data
Importing or Exporting
Makes a copy of a data set and may include changing the format of the data model. Both done using feature class to feature class tool
Assuming target table is on the left, states to cities is an example of which type of cardinality.
Many to 1
MAUP
Modifiable Area Unit Problem: maps reflect the influence rather than data being mapped
MAUP stands for:
Modifiable Areal Unit Problem
Common Geograhpic Coordinate System for US
NAD 1983
Which resampling method should be used on categorical data?
Nearest neighbor
In an attribute table, dividing each value by the total of all the values is another way to _______ data.
Normalize
Common Projected Coordinate System for US
North American Equisdistant Conic
Interval Data
Places values along a regular numeric scale (elevation). can have negative values. Examples are temperature, population change
Ratio Data
Places values along regular scale with meaningful zero point and no negative values. Population of state capitals
What type of coordinate system are rasters usually stored in?
Projected coordinate system that preserves area or distance.
Which methods are used to extract or subset data from a dataset?
Queries, manual selection, and clip
3 types of Extracting Data
Queries: expression based on attribute field Clip: extracts features within a bounding polygon from another feature class Erase: extracts the features outside of a bounding polygon from another feature class.
Map Scale
Ratio of distance on map to distance on the ground. Dimensionless. 1 cm on map= 100,000 cm on ground
Rows are called?
Records
Two types of vector data formats are _____ and _______
Shapefiles and geodatabases
Match data type with map type: Nominal: Categorical: Numeric:
Single Symbol Unique Values Graduated Symbols
Common Projected Coordinate System for local areas
State Plane and UTM's
Data rasters
Store values representing measurements or categories and can be analyzed (ex: elevation, aerial imagery, land use, roads
SQL acronym
Structured Query Language
Shape_area and shape_length fields are not auto recalculated for geodatabase feature classes after processing.
T/F: False
Geographic Coordinate Systems are based on spherical coordinates and measured in latitude and longitude.
True
T/F: Boolean Operators are used when multiple conditions must be tested.
True
T/F: Quantile classification puts the same number of features into each class.
True
T/F: Shapefiles consist of more than one file.
True
T/F: Logistical Consistency assesses how well data represents real-world relationships.
True, for example: do roads connect at intersections?
T/F: Thematic accuracy is not related to data location
True, thematic accuracy is related to accuracy of the attributes. Geometric accuracy is related to a feature's location.
Ordinal Data
Type of categorical data: Ranks categories using along a scale and uses a unique values map
Common Geographic Coordinate System for World
WGS 1984
When GIS servers provide data over the internet (streaming data), this is an example of a?
Web Service
Feature Dataset
a collection of feature classes in a geodatabase that share the same coordinate system and area extent
Vector model
best for discrete data. features are stored map objects (points, lines, polygons) 1 to 1 relationship between feature and row in table
Calculate field tool
can be used to enter an expression to calculate new values for a field in a table. can use existing fields in the expression.
Standard Deviation
compares values close to and far from the mean. (<0.5 std dev or 0.5-1.0 std devs)
3 types of projections are Azimuthal, ____, and ______.
conic and cylindrical
completely contains
contains but doesn't permit a shared boundary
Define Projection Tool vs Project Tool
define projection: 1. creates or changes only the CS Label 2. does not change coordinates in the file 3. Keeps original data set 4. use only when CS is missing or incorrect Project: 1. Changes coordinates in the file 2. Changes the label 3. Creates new data set 4. Use when changing a CS permanently. 5. used to assemble collections of data with the same stored CS.
target tables is known as
destination table and receives the additional information
Geocoding
displays addresses on a map by matching postal data fields in a table to a street data set
Normalizing by Field Percentage
dividing each value by the total of all values. (Number of congressional districts in each state by total # of districts to get percentage of congress in each state)
attribute query
expression is used to find records with values meeting a specific condition (counties with more than 100000 people)
A _____ can be a point, line, or polygon and represent a vector object or location on a map.
feature
What corresponds to a shapefile?
feature class
A ______ stores feature classes that have the same coordinate system and the same spatial extent
feature group
Columns are called?
fields
A ______ is the native data structure for ArcGIS and is the primary data format used for editing and data management
geodatabase
Raster Model
geographic space quantized into uniformly sized discrete units called pixels. Each pixel contains a numeric value that can be an int or float.
Feature Class
homogeneous collections of common features, each having the same spatial representation, such as points, lines, or polygons, and a common set of attribute columns
3 basic operators that test spatial relationships
intersect, contains, and proximity
one to many joins
many records in join table match one record in the target table, use a relate here in which the tables are linked together but remain separate. (congressional districts to states)
projection
mathematical conversion of points on the earth's surface to flat plane (map)
many to many
multiple records in one table can link to multiple records in another table. (each student takes many classes and each class has many students)
Geometrical Interval
multiplies each class range by a constant, best for visualizing strongly skewed or log increasing data like population density
Nominal Data
names or uniquely identifies objects. (Country Names, capital cities, rivers, water bodies). usually portrayed on single symbol map
Many to 1 joins
one record in the join table matches many records in the target table. (Joining states to congressional districts)
1 to 1 join
one record in the join table matches one record in the target table. (joining married to counties using FIPS)
Geodatabases
recommended model for storing spatial information for ArcGIS. containing many types of data (feature classes, rasters, tables)
Rasters always take the shape of a
rectangle
intersect operator
relational set operator that yields only the rows that appear in both tables, tests whether feature touch
Dissolving
removes boundaries of features with the same value in the specified attribute fields.
Quantile
same number of features in each class (Linear data distribution)
spatial query
selecting records or objects from one layer based upon their spatial relationships with other layers (rather than using attributes) (cities within 50 miles of earthquake)
6 field data types
short (2 byte binary) long(10 byte binary) float double float text date
standalone tables
simply store tabular data from any source.
join table is known as
source table and provides the additional information
Picture rasters
store color values (like taking a picture of a map) and cannot be analyzed (ex: scanned topo map, basemap)
Attribute tables
store data associated with a spatial feature class.
Geoid
surface modeled from gravity differences and is closest to true shape but too complicated for mapping.
example of target and source layer: map with counties that contain volcanoes
target = counties source= volcanoes
Contains/within
tests whether a feature is inside another
proximity
tests whether features are within a specified distance of another
source layer
the one containing the features being compared to
target layer
the one from which the features will be selected
Interactive query
the user visually identifies the desired features in a map or records in a table (states west of the mississippi)
Datum
to minimize discrepancy between geoid and ellipsoid these are used. datum shifts the ellipsoid relative to the geoid to achieve best fit. a geocentric or world centered datum optimizes fit for entire earth.
Shapefiles
vector feature classes developed for the early version of ArcView and have been carried over into ArcGIS. Stored in spaghetti data format. Appear as one file in Catalog but are composed of many.
raster resolution
x and y dimensions of each pixel, the precision is limited by this too. Increasing this increase storage requirements.
Are rasters always rectangular
yes