DIGITALPLANETStudyGuide.pdf GEOG 1084
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This 6 page Study Guide was uploaded by Jarrodd Davis on Thursday February 25, 2016. The Study Guide belongs to GEOG 1084 at Virginia Polytechnic Institute and State University taught by Dr. Valerie Thomas in Spring 2016. Since its upload, it has received 126 views. For similar materials see Digital Planet in Geography at Virginia Polytechnic Institute and State University.
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Date Created: 02/25/16
Digital Planet Midterm Study Guide FOR/GEOG 1084 Prepared by Jarrodd Davis DIGITAL PLANET: Tobler’s First Law of Geography: “Everything is related to everything else, but near things are more related than distant things” Tobler’s first law ties into the ideas of spatial autocorrelation and serial autocorrelation. Spatial autocorrelation – values measured nearby in space are more similar than values measured farther away from each other in space Serial autocorrelation – values measured nearby in time are more similar than values measured farther away from each other in time Definitions: Geostatistics (spatial analysis): o statistical study of spatial or spatiotemporal datasets Interpolation: o creating a continuous surface from a set of points Interpolation relies on the assumption of autocorrelation Geospatial Technologies: o systems that acquire, analyze, manage, store, or visualize various types of location-based data Some examples of Geospatial technologies include GPS, remote sensing, and GIS THE INTERNET THE WEB The hardware that provides the Service that is provided by the web. Includes a collection of internet. Does not refer to the computers and cables, a network hardware used by the service. of networks. Does not refer to the service that the hardware provides 1 | P a g e Created by Jarrodd Davis for FOR/GEOG 1084 Virginia Tech College of Natural Resources and Environment Digital Planet Midterm Study Guide FOR/GEOG 1084 Prepared by Jarrodd Davis Digital divide: o Social issue referring to the difference between those who have ready access to computers and those who do not Internet Protocol (IP): o Rules and standards that govern the web **VERY IMPORTANT** The Four Vs of BIG Data: The goal is to make social, environmental, and economic data available and accessible to all Velocity Variety Value Volume Velocity: o Analysis of the speed of data speed of change transaction speed rate of change Value: o Accuracy and relevancy of data Do you trust the data and is it quality data? Volume: o Scale of data Amount of traffic Amount of data held Variety: o Alternate data forms Tweets Video 2 | P a g e Created by Jarrodd Davis for FOR/GEOG 1084 Virginia Tech College of Natural Resources and Environment Digital Planet Midterm Study Guide FOR/GEOG 1084 Prepared by Jarrodd Davis Health data Different types of GIS Data include: Vector data o Points o Lines o Polygons Raster data o Image o Satellite Global Positioning Systems (GPS): There are 32 satellites orbiting above Earth at any given time Trilateration: o Four satellites are required to determine the exact location and elevation of a GPS receiver Receiver: o Device that receives signals from satellites in order to calculate a specific location Precision: o Repeatability of a measurement Accuracy: o Measure of how correct a measurement is Differential GPS (DGPS): o an enhancement to the GPS that uses a network of ground-based reference stations to broadcast differences between satellite systems and known fixed positions DGPS improves receiver accuracy Satellite geometry: o Arrangement of satellites Accuracy is improved if satellites are spaced farther apart to easier pinpoint the location of receivers 3 | P a g e Created by Jarrodd Davis for FOR/GEOG 1084 Virginia Tech College of Natural Resources and Environment Digital Planet Midterm Study Guide FOR/GEOG 1084 Prepared by Jarrodd Davis Different kinds of GPS Errors: Ephemeris errors o error involving orbital position of a satellite Satellite clock errors: o Clocks in receivers run at different speeds than the clocks on satellites (which are much more advanced) Remember that receiver location accuracy is dependent on measurements of satellite signal time and location. Ionosphere & troposphere: o Atmosphere refracts signals and can cause signal to be longer than normal Multipath: o GPS signal bounces off a reflective surface prior to reaching the receiver this is problematic in urban areas where there are skyscrapers and in forests Selective availability: o Until 2000, the government intentionally caused inaccurate readings to private GPS receivers due to concern for public safety Location-Based Services (LBS): We can use LBS technology for environmental applications o Real-time reporting of environmental conditions o Weather o Emergencies/alerts Many common workflows are applicable for environmental applications o Asset tracking (including workers or animals) o Mobile data access o Data maintenance o Monitoring Data collection apps can also be integrated with GIS Entity vs. Continuous Field An entity has sharp boundaries A continuous field has a gradient that represents change over topology In a vector data model, features are defined by coordinate pairs o Vectors better depict entities In a raster data model, features are depicted by contents of grid cells 4 | P a g e Created by Jarrodd Davis for FOR/GEOG 1084 Virginia Tech College of Natural Resources and Environment Digital Planet Midterm Study Guide FOR/GEOG 1084 Prepared by Jarrodd Davis o Rasters better depict continuous fields Data Modeling: Point: o A single vertex Value depends on coordinate system Do not have length or area Attributes describe the points Line: o Series of connected vertices Do not describe enclosed shapes Line features don’t have area Contains 2 or more vertices Polygon: o Series of vertices that describe a shape Have area & perimeter Often have shared geometry Contains 4 or more vertices Digitizing: o Process of creating or editing the geometry of vector data Can be manually input or loaded automatically Allows you to create your own data Also allows you to clean/fix messy data There are many different types of geometric inaccuracies in vector data: Instrument error Digitizing error Scale mismatch Inaccurate data source Seasonality Vector features have geometry (points, lines, and polygons) and attributes Dotum: o Smooth mathematical surface that closely fits the mean sea level surface through an area of interest Metadata: o Data about data Project coordinate system Datum Units 5 | P a g e Created by Jarrodd Davis for FOR/GEOG 1084 Virginia Tech College of Natural Resources and Environment Digital Planet Midterm Study Guide FOR/GEOG 1084 Prepared by Jarrodd Davis Buffer zone: o An area around real world features Always vector polygons One feature can have multiple buffer zones Size defined by buffer distance Remember our in-class exercise where we examined Blacksburg for homes within 500 feet of a bike trail Raster data model o Advantages: Simple data set: matrix of cells with values sometimes linked to an attribute table Powerful for advanced spatial and statistical analysis Ideal for continuous field values o Disadvantages: Spatial precision limited by raster dataset cell dimensions Large datasets quadruple in size as horizontal dimension of resolution increases As you move from smaller to larger cell size, you lose: o Precision spatial accuracy and data Raster buffer must buffer out in cell size increments Zone: o Each different value assigned to a grid cell Region: o Multiple touching zones with the same value Boolean operators: o Terms that expand or constrict data and or xor (one or the other) not is is not 6 | P a g e Created by Jarrodd Davis for FOR/GEOG 1084 Virginia Tech College of Natural Resources and Environment
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