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.