Chapter 1 Flashcards
3 Vector Features
Features, Line, point, and polygon
Absolute Pathname
Starts at the drive letter and proceeds toward the file
Active Frame
All commands and actions, such as adding layers, occur only in the active frame.
Affinne
In transformation from Ground control p lints, ArcGIS uses a mathematical transformation. An affine is a first-order transformational.
ArcMap compatibility between newer and older versions
ArcMap is backward compatible, but not forward compatible. Newer version can open map documents saved in earlier versions, while older version cannot open map documents in newer versions. Solution is to save files in old format.
Aspatial Data
Data not tied, or only incidentally tied, to a location on the earth’s surface. (Address for billing is arbitrary)
Attributes
Information about objects in a feature class (population of a city)
Bands
A single array of values stored in a raster, which may store one array or many
Categorical Data
Categorical data separate features into distinct groups or classes. Volcano type, road class, land cover (forest, grasslands, urban). Often stored as text, but can also be coded. Represented by a unique values map, which gives each category a different symbol based on shape, line type, color, or pattern.
Central Meridian
A projection parameter that constitutes the central position center of the area being mapped
Chart Map
Uses a chart, such as a pie graph within a map. For example, ethnic make-up of. a state.
Chorpleth Map
Thematic map in which areas are shaded or patterned proportionally to the value of an attribute.
Classified Display
Divides the values of values into a small number of bins, similar to a graduated color map. Raster.
Common Datum
NAD 1927 (based on the Clarke 1866 Spheroid. NAD 1983 is based on the more accurate GRS 1980 spheroid. World Geodetic System 1984
Connotation
Emotional impact associated with a symbol such as red for danger in the US but joy in Thailand.
Continuous Data
Data that represents quantity that is measured and recorded everywhere over a surface.
Continuous Raster
Stores values that are continuously varying, such as elevation, temperature, geological features.
Convention
Use of a particular color or symbol with certain meaning
Coordinate Pairs
A single x, coordinate pair used to specify the location of a feature
Coordinate Space
Agreed-upon range of coordinates in specified units used to portray features. The range of x,y features onto which a map is plotted.
Coordinate System
The choice of values and units to store a data set. 1.) A specified range of x-y values onto which a map is plotted; 2.) The definition of coordinate space used by a map layer, including a ellipsoid, datum, and projection
Coverage
Vector data developed for Arc/Info and is the oldest of the data formats. Now typically converted to a shape file.
Data Analysis
Functions for exploring spatial relationships in and between map layers
Data Classification Methods
Jenks Method Equal Interval Defined Interval Quantile Geometric Standard Deviation
Data Entry’s Contribution
From a variety of sources you can create data to be used in GIS and a way to export information to other programs. Cannot analyze data, create maps, etc if there is no data to work with.
Data Management Tools
Manipulate data into a usable format
Database Connections
User can connect to a database management system on a network.
Datum
A combination of an earth ellipsoid (spheroid) and a reference point to reduce mapping discrepancies. Because the true surface of the earth is irregular, its surface can only be approximated. Different approximations have been to meet specific mapping needs. This approximation is called a datum. A sphere is converted into a spheroid and then shifted relative to the geoid until a best-fit solution is obtained. A datum consists of the chosen spheroid and the location of its center relative to the geoid center. A datum is a GCS.
dBase
Database file whose file format has been adapted for the shapefile model and tables in ArcGis. Exists within a sphapefile and is a table that contains attribute data.
Define Projections Tool
Once coordinate system is known, the user may create the coordinate system label with their tool.
Defined Interval
User specifies the size of classes and number of classes. Ideal when classes comparing things such as money, temperatures, that are easy to interpret.
Difference Between a Map Document (.mxd) and Map Package (.mpk)
Map document (.mxd) (or a layer file) does not store GIS data files within it. Instead the map stores the name and location data (the source). A map package (.mpk) includes the map document as well as the data needed to produce them map.
Digital Elevation Model (DEM)
A raster array of values representing elevations at the Earth’s surface
Digital Raster Graphic
A scanned image of a USGS topographical map
Discrete Data
Data that are objects in the real world with specific locations or boundaries.
Discrete Rasters
A raster that stores (non-continuous) objects such as roads or polygons.
Distortions Produced by 3 Types
Cylindrical - Preserve direction and shape at expense of distance and area (longitude boxes point in the right direction but become enlarged, so distance and area don’t work) Conic - Preserves area and distance at the expense of distance and shape) Azimuthal - Preserves areas or distances.
Divergent Color Set
Used for showing variation around a significant middle value. For example change in temperature, colder or warmer, from current temperature
Dot Density Map
Uses randomly placed dots to show the magnitude of a value in the attribute table. Every thousand people gets a randomly placed dot.
Elements needed to do a Projection
A reference globe A developable surface A Source of light
Enterprise GIS
Long-term GIS project developed by a large organization involving many people over a large period of time
Equal Interval Method
Classifies values into a specified number of classes of equal size. Different numbers of features in each class. Useful for ration data such as income or population because it gives a sense of regularity.
Extent
Extent of data layer is the range of x,y coordinates actually in the feature class.
False northing or easting
Arbitrary numbers added to x,y coordinates in order to translate the map to a new location in the coordinate space. Often done to ensure all the coordinates of the map are positive.
Father of GIS
Dr. Roger Tomlinson
Feature
Spatial object composed of on or more x,y coordinate pairs and having one or more attributes in a single record of an associated table
Feature Class
Set of similar objects with the same attributes stored together in a spatial data file
Feature Dataset
A set of feature classes in a geodatabase that share a common coordinate system and can participate in networks and topology
Feet in a mile
5,280
Feet in a yard
3
FID or OID
Feature and Object IDs. Links the spatial data with the attributes.
Five Components of GIS
Data entry; Data management; Thematic Mapping; Data Analysis; Map Layout
Flow Map
Shows the movement of Objects from one location to another
Generalization
Simplification of data for digital storage. For example, a city is a point or a river a line instead of a polygon.
Geocoding
The matching of a description of a location stored in a table to a spatial point feature based on a reference spatial data layer.
Geodatabase
Represent an entirely new model for storing spatial information with additional capabilities. Can contain many different objects including features classes, networks, tables, rasters, and topology.
Geographic Coordinate System
Spherical coordinate system of degrees of latitude and longitude that is used to locate features on the earth’s surface.
Geoid
The closest approximation to the earths’ shape. An irregular, equipotential surface based on gravity. What the earth would look like if there were only seas and no continents.
Geometric Accuracy
Describes how well the x-y coordinate values of a dataset correspond to the actual location on the earthy’s surface.
Geometric Interval
Bases the class intervals on a geometric series is multiplied by a constant coefficient to produce the next higher class. Works well with continuous data like precipitation and positively skewed data distributions. Provides about the same number of values in each class range.
Georeferenced
Information is tied to a specific location using x-y coordinates defined in a standard way
GIS Project Management Steps
Identify Project Needs->Develop Suitable model->Collect data (Evaluate data: Correct? Need more)->Perform Analysis (Evaluate Results, Re-evaluate data and project needs)->Present Results
GIS Project Model
Steps or calculations used to convert raw data into useful information; a scheme used to understand and predict processes in the real world based on the manipulation of data
GIS Server
Provide GIS Data over an internet connection as maps, features or images. Several types of services available: Map services renders map layers and sends them to user as static images. Feature Service shares requested data features (can change them) Layer or map package (sends data to a client where it is stored locally during use) Image service provides access to satellite imagery and aerial photos. Geoprocessing Services makes available certain computation and functions so user can perform analysis through a website.
Goal of GIS
Provide the means to collect, manage, and analyze data for better decision making.
Ground Control Points
User-created ground control points to match locations on different images or features classes that has a real-world coordinate system.
How does ArcGIS handle projection:
Projection of data frames and layers. The first layer added to a data frame defines the frame’s coordinate system. Then all other layers will be projected on-the-fly to match this. Projecting on-the-fly - A data frame may be assigned any desired coordinate system and ArcMap will project all data in the frame to match. Tools in ArcGIS to Change Projection Information - Define Projection Tool - Doesn’t project but simply puts a label on the shape file without changing coordinates. - Project Tool - Converts x,y coordinates in a feature class to a different system and saves a new feature class with a new coordinate system label. - Project Raster Tool
Image Raster
Includes aerial photography and satellite data. A pixel represent a degree of brightness.
Import/Export
Process of copying a file into a new location and simultaneously converting data storage formats.
Interchange File
Arc/Info used a proprietary zipping/conversion format to convert coverages into a text file, known as an interchange file.
Internet Data Service
Data available online
Interval Data
A type of quantitative data that has a regular scale, but are not related to a meaningful zero point. Temperature. 80 isn’t twice as hot as 40.
Isarithmic Mapping
Represents a continuous field using lines to connect places of value. Created by interpolating from raster data from a set of sample points. Isolines join all connected points of the same value (measured or interpolated)
Item Description
Metadata. Users can quickly review the most important information, such as Summary (Brief summary describing the purpose of data or intentions for which it was developed) Description (More extended explanation of the data including what the data contains, how it was developed, what the attributes mean, information about data quality such as source scale). Credits (Source of the data) Appropriate Scale Ranges (suggests the scales at which the data are valid) Bounding Box (Automatically entered from the x,y extend of the features. It is always in degrees). Use Limitation (Any information on limits placed on the data such as whether it can be copied or shared).
Jenks Method
Classifies numeric data, sets the class breaks at naturally occurring gaps between groups of data. Each class interval can have its own width and numbers of features in each class will very. Works well on unevenly distributed data such as populations of state capitals (many low population, few higher population)
Large-Scale Versus Small-Scale
1:24,000 is larger scale than 1:100,000. Larger scales shows smaller area.
Latitude
vertical angles below or above equator (zero degrees) to the poles (90 to -90 degrees)
Latitude of Origin
Also called reference latitude. This is the y=0 line. Often the equator.
Layer
Feature class or raster that is added to ArcMap. A layer points to a feature class and stores information about how to display and use it.
Layer File
A layer may be saved a layer file. This file stores the location of the data set upon which the layer is based and the properties of a layer.
Layer Properties
Information stored about what symbols, labels, etc, features should have.
Layers vs Shapefile
A shapefile is a vector data storage format that contains the location, shape, and attribute of a feature. Contains several files within in itself. Contains one feature class. A layer is simply a reference to data such as a shape file or raster that defines how the data should be symbolized on a map.
Layout
The specification for a map page, including map frames, legend title, scale bar, etc, stored in a map document.
Layout View
Mode in ArcMap that is used to design and create a printed map and that allows the manipulation of map layers, titles, scale bars, north arrows, etc.
Local Datum
A datum that is the best fit of the spheroid to the geoid for a particular region.
Lock File
If a file is being used, it creates a lock file so that others cannot simultaneously make changes for access the file.
Logical Consistency
Evaluates whether a data model or data set accurately represents real-world relationships between features.
Longitude
Angles of horizontal areas east or west of the Prime Meridian (zero degrees)
Map Document
File used by ArcMap to contain a set of data for mapping and analysis. A collection of spatial data layers and tables and their properties. A document is designed to contain a single map page, called a layout.
Map Layout
Functions for creating hard and soft copy maps with various map elements.
Map Scale
The ratio of feature size on a map to its size on the ground. (1 in is equal to x in real life)
Map Units
Units of the coordinate system in which a map is stored
Map Units
The unit of the x,y
Metadata
Stores information about the data set, where it came from, how it was developed and for what purpose, how precise it is, and whether it can be used.
Methods for designating Color
RGB - Red, Green, Blue. Used for computer screen. CMYK - Cyan, magenta, yellow, black. Often used for printing and specifies mixtures of ink used in printers. HSV - Hue, Saturation, Value. Hue is shade of color (wavelength of light). Saturation corresponds to the intensity of the color measured as a percentage. If mixing paint a small amount of pigment would yield a small amount of saturation. Value is how light or dark the color is, transitioning from the full color to black.
Modifiable Areal Unit Problem
Measurements aggregated over arbitrarily sized area (population of California versos North Dakota)
Nominal Data
Nominal data identify objects, such as names of a state, address, or phone number. Often used as labels on various map types
Normalize
Dividing data by another variable
Object-Oriented Programming
A programming and database approach that treats software and model elements as objects with defined properties and relationships.A programming model in which related tasks, properties, and data structures are enclosed inside an object, and work is done when objects make requests and receive results from other objects. For example, a billing program may contain an object that maintains customer records. That object may pass information to another object that handles mailing statements, and another object that handles customer payments may ask it to update a customer record when a payment is received.
Ordinal Data
Ordinal data have categories that are ranked based on some quantitative measure, although measure may not be linear. Village, town, city, Grades, A,B,C,D,F. Must be represented by unique value maps if the values are text. Numerical ordinal data can be either unique value map or graduate color map.
Origin
Coordinate 0,0
Paramaters
Specific value associated with map projections that define how it appears. Can include: Central Meridian Latitude or Origin (or reference latitude) Standard Parallels
Parts of a line
Two or more pairs of x,y coordinates. To ends are nodes and ones in between vertex
Pathname
Location of file
Point
Single x,y pair. Point features represent objects that have no demensions.
Polygon
Group a vertices that defines a closed area. Polygon feature are used to represent two-demensional areas such as a parcel
Precision
Refers either to the number of specific digits to record a measurement or statistical variation of a repeated single measurement. Not to be confused with accuracy. A temperature of 99.893 would be precise, but not accurate if you had just drank a hot coffee.
Process of Projection
Start with define GCS and apply a mathematical formula that converts degrees of latitude and longitude into planar x,y coordinates. Converting three-dimensional GCS positions in degrees into feet or meters. The GCS influences exactly where locations end up on the paper, so the GCS is inherited by the projection.
Projection
The process of converting the locations on a globe to a flat piece of paper.
Quantile Method
Puts about the same number of features in each class. Enables the display of groups, such as quartiles. Balanced map with all classes equally well represented, however, some features in the same class could have very different values, or features in different classes could have similarly values. Best for uniformly distributed data.
Raster
A dataset composed of an array of numeric values, each of which represents a condition in a square element of ground
Raster
Map data or imagery using arrays of regular cells containing numeric values
Raster Model
A data model that uses rasters or numeric arrays to represent real-world features. Data is represented as a series of small squares called cells or pixels. Each pixel contains number indicating a single attribute
Raster model
Model designed to store continuous data.
Raster Resolution
X and why dimensions of each pixel define the resolution of the raster data. The higher the resolution the more precisely the data can be represented. If a pixel is at 90-meter resolution, a feature would be represented as much wider than they are.
Ratio Data
A type of quantitative data that has a meaningful zero point. Can support addition, subtraction, multiplication and division.
Read and Write Access
Read Access allows a program to take information out of a file without changing it. Write Access allows changes to be made to a file.
Rectify
In georeferencing, the final step, one rectifies the image by rotating, resizing, or warping to match. During rectification, the raster is converted from one grid of cells to another with potentially different sizes and spacing, forcing the cells to be adjusted or resampled.
Relative pathname
Indicates the search for a file should begin at a certain level.
Resolution
Refers to the sampling interval at which data are acquired. May be spatial, thematic, or temporal. Census data every ten years, temperature data every 15 minutes, reported as average, what size is a pixel of satellite photo.Represents underlying accuracy of the values.
Root Mean Square Error (RMSE)
When transformations are applied to ground control points, an offset is always found between specified locations and actual locations. This offset is evaluated by RMSE. Reported in map units of the new coordinate system.
Rubbersheeting
In georeferncing, process of deforming a raster to make it fit a new coordinate system.
Shapefile
Shapefiles are spaghetti data models containing a feature class composed of points, lines, or polygons (Vector). Data stored in a dBase file. Can store multipart features in which a single feature includes multiple objects (multiple polygons for islands of Hawaii, multiple cities). Although seen as a single icon in ArcGIS, a shape file is multiple files. Spatial data model developed for ArcView3 and later versions
Shapefile components
.sph (coordinates data); .dbf (stores attribute data) .shx (stores spatial index) .prj (projection information) .avl (Legend) .xml (metadata)
Source
1.) Spatial data file that provides the features for a map 2.) The original information used to develop a spatial data set
Source Scale
Original analog scale ore resolution at which a digital dataset is converted into digital form.
Spaghetti Model
Model that stores spatial features as a series of x,y coordinates and does not store topographical relationships between features
Spatial Data
Data Location tied to a specific location on the earth’s surface
Spatial Reference
Includes x,y domain, the coordinate system, and the resolution.
Standard Deviation Classification
Apportions values of classes based on the statistics of the field. The user selects the class breaks as the number of standard deviations and the data range determines the number of classes needed. This method excels at highliting which values are typical and which are outliers, especially since a divergent color set is used to accentuate below versus normal.
Standard Parallel
Line of tangency.
Stretch
In georeferencing, spreading the values of an image to cover the entire range of symbols available.
Stretched Display
Scales the image values to a color ramp with 256 shades. Raster is sliced, which rescales the elevation values then matches to colors. Can use this on images by stretching the color bands included in the image to make them more apparent.
Tables
Can exist as separate data objects that are unassociated with a spatial data set
Thematic Accuracy
Refers to attributes and how accurately recorded.
Thematic Mapping
This is displaying data in map form. Displays the features of a spatial data layer based on values in its attribute table. Focuses on a theme rather than geography.
Thematic Raster
Represents features or quantities such as roads, geology, or vegetation.
TINs
Triangular Irregular Networks that store 3D surface information, such as elevation, using sets of nodes and triangles.
Topological Model
Data model that stores spatial relationships between features in addition to their x,y coordinates
Topology
The spatial Relationship between features. Information about how features are spatially related. (adjacency, overlap, connectivity, intersection etc)
Transformation
Conversion from one datum to another
Two basic Vector Models
Spaghetti Model and Topological Model
Two Commonly Used Projected Coordinate Systems
Universal Transverse Mercator (UTM) - Based on a secant transverse cylindrical projection. Two lines of tangency fall about 180km each side of the central meridian. . A zone is defined to include 3 degrees on each side of central meridian. Therefore, 60 zones. State Plane Coordinate System - Developed for large-scale mapping in the United States. Can use Lambert Conformal Conic, Transverse Mercator, or oblique Mercator. East-west oriented zones use Lambert Conformal Conic. North-South use Transverse mercator. States can use more the one.
Types of Color Sets
Category (can be mixed); Quantity (should be shades); Divergent (shades going in two different directions.
Types of Conic Projects
Tangent Conic - The cone is set on a sphere. If the cone is tangent to the globe along a line of latitude. Secant Conic - The cone is placed through the sphere so there are two tangents.
Types of Cylindrical Projections
Cylindrical - Uses a cylindrical surface that lies tangent (touches the earth at the equator along a great circle. Rotating the cylinder sideways making It tangent to a line of longitude produces a transverse cylindrical projection. Oblique cylindrical places the tangent at an angle.
Types of Data
Nominal Categorical Ordinal Ratio Interval
Types of Data Files
Shapefiles Coverages Geodatabase Database Connection Layer Files Rasters Tables GIS Servers TIN (Triangulated Irregular Network) CAD
Types of Distortions
Area, Distance, Shape, Direction
Types of GIS Professionals
Primary Data Providers (surveyors, etc); Application GIS (people who use GIS as part of their jobs); Development GIS (actually build and maintain GIS software); Distributed database GIS (networking for Enterprise GIS);
Types of Maps
Proportional Symbol (Point or line data). Actual data used to determine size of symbol. Not arbitrary Graduated Symbol (Usually point or line data) Choropleth Map Graduated Color (Choropleth Map) Dot Map Flow Mapping Isarithmic Mapping Chart Mapping
Types of Projection
Cylindric Conic Azimuthal (stereographic, orthographic) Uses plane that is tangent or secant to a sphere.
Types of topological relationships
Adjacency; Connectivity; Overlap; Intersection
Unique values Raster
Represents ordinal or categorical data, such as geological categories.
Universal Transverse Mercator
Family of map projections defined for 60 zones around the world and based on a transverse cylindrical projection
Unprojected Data
If data is unprojected, coordinates are labeled in latitude and longitude.
Use of Data Frames
You can add separate data frames to display multiple maps on one page.
Vector Model
Model designed to store discrete data.
Web Map
Interactive map based solely on GIS services.
What is GIS?
A set of computer tools that allows people to work with data that are tied to a particular location on earth.
Which UTM zone is Illinois? Which SPCS is Sangamon County
UTM Zone 16N (and a bit of 15N) SPCS Zone - Illinois West
World File
Six-line text file that contains the parameters to georeference a raster.
X/Y Domain
Range of allowable x,y values that can be stored in a f feature class.
Zipping
Process that combines many individual files into one.
