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66 Cards in this Set
- Front
- Back
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database
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a set of structured or related data
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spatial data v. tabular data
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where things are v. what things are
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database management system
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software application designed to organize the efficient and effective storage retrieval, indexing and reporting of data
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The Relational Database Model (
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Each COLUMN has a unique name
Column entries MUST be drawn from same domain Columns can be in ANY order Only ONE entry per cell Each ROW must be distinctive NULL values are allowed |
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queries
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• Primary method of data
retrieval • Create new information, but doesn’t change the older/existing information • Type of Queries – Spatial – Aspatial |
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Primary Key
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– Unique Identifier for EACH row of information a particular data file
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Foreign Keys
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– Non‐unique Identifier that carries information that may be linked to the primary key
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Arc Catalog
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ArcCatalog is an application that allows you to Explore, Access, Manage, and Build geographic data
• Seamless view of geographic data, similar towindow’s explorer • Icons communicate the role of individual GIS elements • No Microsoft clutter |
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Functions of ArcCatalog
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• Create & format new data
• Search for data • Determine geographic extent • Determine data quality • Launch GIS operations |
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Geodatabase & components
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A Geodatabase is the top level unit of geographic data
organization. It is a collection of Datasets, feature classes, object classes and relationship classes |
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Feature Dataset
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A collection of feature classes that share a common coordinate system
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Feature Class
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A collection of features with the same geometry
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Object Class
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A table within a geodatabase that relates to the spatial data
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Relationship class
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A table that stores relationship information between
features and objects. Relationships model the dependencies between objects |
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Metadata?
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Documentation of the content, quality, condition of the data
– Who made it? Who distributes it? – What is the subject, processing? – When and where was it collected? – Why and how was it collected? – How much does it cost? – How is it referenced to the real world? – What’s the quality of the data? – Who should I contact if I have questions? |
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Spatial Analysis?
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Spatial Analysis is the process by which we turn raw
geographic data into useful information; it includes all the manipulations and methods that can be applied to Geographic data, to add value, support decisions, and reveal patterns and anomalies not immediately obvious |
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Scope
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• The geographical extent or area of the input data used to determine the values at output locations
Characterization of Scope • Local • Neighborhood • Global |
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aspatial queries using query algebra
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-set algebra (<,>,=,<>)
-Boolean queries (or, and, not) |
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spatial queries using query algebra
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adjacency and containment
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proximity functions
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buffers and spatial joins
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buffering
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creation of a zone of interest (inclusion or exclusion) around an entity
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Clipping
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This process creates a new layer by using a polygon layer
(or selected polygons from a particular layer) as a cookie cutter on a point, line, or polygon shapefile. The output layer contains information from Layer A only. Layer B is only used to define the new boundary |
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Intersect
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The intersect method preserves only those features falling
within the spatial extent common to both layers. The features of the input layer are intersected or sliced by the intersect layer. The attribute data from both layers are included in the new layer's attribute table. |
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Dissolve
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Dissolving features in a layer coalesces features that have
the same attribute value. This tool is extremely important if you are trying to create a new shapefile, a file with a coarser layer of geography than your starting files |
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Union
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Union creates a new layer by combining two polygon
layers. The new layer has data and shapes from both layers, including their intersection |
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Merge
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Using merge is similar to union; a new layer is created from
multiple layers but their features are not intersected. Merge allows you to combine the features from two or more layers of the same geometric type. |
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Raster Algebra
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The cell by cell
combination of raster data layers using either local, neighborhood, or in some cases global functions |
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Math (Local Raster Functions)
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• Apply Mathematical Functions on a cell‐by‐cell
basis • Most Functions use one input layer – one output layer • Basic Arithmetic • Trigonometric Functions • Inverse Functions • Truncation • Powers |
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Boolean (Logic) (Local Raster Functions)
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• Boolean operations place true or false values
depending on the input values • Three basic logical operators – AND, OR, NOT – Also Logical Comparison |
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Reclassification (Local Raster Functions)
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• Raster Reclassification assigns output values that depend on the specific
set of input values • Based on matching input cell values to a reclassification table • Usually a single output value applies to a range of input values |
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Overlay (Local Raster Functions)
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• Cell‐by‐cell combination of
data from two or more input layers • New output values are generated for each unique combination of input values • Typically Nominal data (categorical) |
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What are Zonal Statistics?
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-A Statistic is calculated for each zone of a zone dataset, based on values from another dataset
Zonal Functions apply operations based on defined regions or zones • Zone = All the cells in a raster that have the same value (do not have to be contiguous) • What Statistics? • Max, Min, Mean, Median, Range, Sum, Standard Dev. |
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Cost‐Distance (Neighborhood Raster Functions)
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• A cost surface contains the minimum cost of
reaching cells in a layer from one or more source cells • Uniform Travel Cost (Simple) – fixed cost per distance • Friction Surface |
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Isarthmic map
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An isarthmic map (contour map) is created by
interpolating a set of isolines between sample points of known values. |
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Isopleth map
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special kind of isarthmic
map in which the sample points are associated with enumeration units |
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Thiessen Polygons
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This method assumes
the values of un‐ sampled area are equal to the value of the closest sampled point |
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Triangulated Irregular Network
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• This method is used to
construct Digital Elevation models • Adjacent data points are connected by lines to form a network of irregular triangles |
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Trend Surface
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This methods attempts to fit a mathematically
defined surface through all the data points |
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Spatial Moving Average
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• The most common
interpolation method used in GIS • Calculates a value for a location based on the range of values attached to neighboring points that fall within a user defined range |
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Density Analysis
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Density analysis takes known quantities of some phenomena and spreads it across the landscape based on the quantity that is measured at each location and the spatial relationship of the locations of the measured quantities.
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Primary Data Collection
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direct measurement
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Secondary Data Collection
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(Derivation from other sources)
Data Capture refers to direct entry, while Data Transfer refers to importing existing digital data |
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Data Sources
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• Primary geography data sources are captured
specifically for use in GIS by direct measurement • Secondary sources are those reused from earlier studies, or, obtained from other systems. |
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Primary
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:::Raster
Digital Satellite remote sensing images Digital Aerial aerial photographs :::Vector GPS measurements Survey measurements Geocoding addresses |
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Secondary
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:::Raster
Scanned maps or photographs Digital Elevation models from topographic map contours ::::Vector Existing Vector Data Coverages, Autocad Manual Digitizing from scanned maps |
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Remote sensing
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Remote Sensing is the measurement of physical,
chemical, and biological properties of objects without direct contact |
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Raster Data Capture (Secondary): scanning
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• Using a scanning devise to convert hardcopy analog
media into digital images • Georeference • Geographic wallpaper • Template for vectorization – Why scan? • Reduce wear and tear, improve access, provide db storage • Provide geographical context • Scan prior to vectorization – Creates a raster data set that can be vectorized (both automated & manual) |
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Georeferencing (Rubbersheeting)
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When you Georeference your raster dataset, you
define its location using map coordinates and assign the coordinate system of the data frame. |
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Vector Data Capture (Primary): Ground surveying and GPS
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Ground Surveying
• Determined by measuring angles and distances from known points GPS • Global Positioning System – GPS System (USA – GLONASS (Russia – 2009) – Galileo (Europe – 2011 ~ 2012) – COMPASS (China) – IRNSS (India) |
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Surveying
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Surveying is the art and science of
measuring the surface of the earth and its features. • Geodetic surveys take into account the true shape of the earth • Plane surveys treat the earth as a flat surface • Horizontal surveys determine the position of features on the ground • Vertical surveys determine the elevation or heights of feature |
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GPS satellite
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• A minimum of 24 GPS
satellites orbit the Earth • At an altitude of approximately 11,000 miles • Provide users with accurate information on position, velocity, and time anywhere in the world and in all weather conditions. |
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Geocoding
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Geocoding is the process of finding associated
geographic coordinates (often expressed as latitude and longitude) from other geographic data, such as street addresses, or zip codes (postal codes). |
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Vector Data Capture
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• Manual digitizing
– Puck on tablet – Easiest, cheapest, simplest… – Stream digitizing vs. click‐click • Heads up digitizing – From a map on your screen • i.e. scanned in map or aerial photograph – Very often the way to go now |
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Vectorization
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– Converting raster to vector data
• Batch Vectorization (Automated process) – Simple (spaghetti) lines are built from pixels |
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Accuracy
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the degree to which information on a map or in a
digital database matches true or accepted value |
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Precision
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refers to the level of measurement and exactness
of description in a GIS database **high level of precision DOES NOT imply a high level of accuracy |
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Bias
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consistent error throughout a dataset
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Modifiable Areal Unit Problem (MAUP)
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– Problem associated with aggregate data sources
– Use of Arbitrary spatial units – Problem of Scale |
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Ecological Fallacy
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errors due to performing
analyses on aggregate data when trying to reach conclusions on the individual units |
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passive remote sensing
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natural radiation measured
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active remote sensing
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– Sensing device emits
energy – Measures the backscattered radiation |
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Unsupervised image classification
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Creates polygons of similar features
– Based on the reflectance properties of the objects |
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Open source software
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computer
software for which the human‐readable source code is made available under a copyright license (or arrangement such as the public domain) that meets the Open Source Definition. • This permits users to use, change, and improve the software, and to redistribute it in modified or unmodified form. It is very often developed in a public, collaborative manner. |
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government gis use
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• Economic Development
• Transportation and Services Routing • Housing • Infrastructure • Health • Tax Maps • Human Services • Law Enforcement • Land‐Use Planning • Parks and Recreation • Environmental Monitoring • Emergency Management • Citizen Information (Geodemographics) |
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manhattan distance
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counting blocks, like legos
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Spatial join
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kind of like sister to select by location .if there's nothing in the database that helps you tie things together, you have to use the notion of geometry to answer data questions
-count # of schools within a county -Count # of zip codes within a state -notion of proximity: ten nearest hospitals in the distance |
