Data Capture

The capture of massive quantities of spatial data, able to be distributed and shared in real time, provide for an ever-increasing range of environmental and societal applications. Data capture includes the principles, methods, technologies, applications, and institutional/programmatic aspects of spatial data acquisition. Sources of data include global navigation satellite systems, satellite and aerial sensing, field surveys, land records, socioeconomic data (e.g., census), volunteered geographic information, wireless sensor networks, and unmanned aerial systems.

Topics in this Knowledge Area are listed thematically below. Existing topics are linked directly to either their original (2006) or revised entries; forthcoming, future topics are italicized. 

 

Digital Data Capture Land Surveying and GPS  
Data capture methods Survey theory and electro-optical methods  
  Land records  
Aerial Imaging Global Positioning System  
Nature of aerial photograph data    
Aerial photography image interpretation Field Data Collection  
  Spatial sample types  
Remote Sensing Platforms & Sensors Sample size selection  
Mission planning Sample intervals  
Nature of multispectral image data Census data  
Multispectral sensors and programs Field data technologies  
LiDAR data Volunteered Geographic Information (VGI)  
Unmanned Aerial Systems (UAS)    
  Data Coordinating Organizations  
  Spatial data sharing among organizations  
Processing Remotely-Sensed Data Federal agencies, National & International Organizations  
Stereoscopy and orthoimagery State and regional coordinating bodies  
Vector data extraction    
Algorithms and processing    
Ground verification and accuracy assessment    

 

DC-12 - Aerial photography image interpretation
  • Use photo interpretation keys to interpret features on aerial photographs
  • Calculate the nominal scale of a vertical aerial image
  • Calculate heights and areas of objects and distances between objects shown in a vertical aerial image
  • Produce a map of land use/land cover classes using a vertical aerial image
  • Describe the elements of image interpretation
DC-18 - Algorithms and processing
  • Differentiate supervised classification from unsupervised classification
  • Describe the sequence of tasks involved in the geometric correction of the Advanced Very High Resolution Radiometer (AVHRR) Global Land Dataset
  • Compare pixel-based image classification methods with segmentation techniques
  • Explain how to enhance contrast of reflectance values clustered within a narrow band of wavelengths
  • Describe an application of hyperspectral image data
  • Produce pseudocode for common unsupervised classification algorithms, including chain method, ISODATA method, and clustering
  • Calculate a set of filtered reflectance values for a given array of reflectance values and a digital image filtering algorithm
  • Describe a situation in which filtered data are more useful than the original unfiltered data
  • Perform a manual unsupervised classification given a two-dimensional array of reflectance values and ranges of reflectance values associated with a given number of land cover categories
DC-22 - Federal agencies and national and international organizations and programs
  • Describe the data programs provided by organizations such as The National Map, GeoSpatial One Stop, and National Integrated Land System
  • Discuss the mission, history, constituencies, and activities of international organizations such as Association of Geographic Information Laboratories for Europe (AGILE) and the European GIS Education Seminar (EUGISES)
  • Discuss the mission, history, constituencies, and activities of governmental entities such as the Bureau of Land Management (BLM), United States Geological Survey (USGS) and the Environmental Protection Agency (EPA) as they related to support of professionals and organizations
  • involved in GIS&T
  • Discuss the mission, history, constituencies, and activities of GeoSpatial One Stop
  • Discuss the mission, history, constituencies, and activities of the Open Geospatial Consortium (OGC), Inc.
  • Discuss the mission, history, constituencies, and activities of the Nation Integrated Land System (NILS)
  • Discuss the mission, history, constituencies, and activities of the Federal Geographic Data Committee (FGDC)
  • Discuss the mission, history, constituencies, and activities of the National Academies of Science Mapping Science Committee
  • Discuss the mission, history, constituencies, and activities of the USGS and its National Map vision
  • Discuss the mission, history, constituencies, and activities of University Consortium of Geographic Information Science (UCGIS) and the National Center for Geographic Information and Analysis (NCGIA)
  • Discuss the political, cultural, economic, and geographic characteristics of various countries that influence their adoption and use of GIS&T
  • Identify National Science Foundation (NSF) programs that support GIS&T research and education
  • Outline the principle concepts and goals of the “digital earth” vision articulated in 1998 by Vice President Al Gore
  • Assess the current status of Gore’s “digital earth”
DC-09 - Field data technologies
  • Identify the measurement framework that applies to moving object tracking
  • Explain the advantage of real-time kinematic GPS in field data collection
  • Describe an application of hand-held computing or personal digital assistants (PDAs) for field data collection
  • Considering the measurement framework applied to moving object tracking, identify which of the dimensions of location, attribute, and time is fixed, which is controlled, and which is measured
  • Describe a real or hypothetical application of a sensor network in field data collection
  • Outline a combination of positioning techniques that can be used to support location-based services in a given environment
DC-03 - Global Positioning System
  • Explain how GPS receivers calculate coordinate data
  • Discuss the relationship of GPS to the Global Satellite Navigation System
  • Explain “selective availability,” why it was discontinued in 2000, and what alternatives are available to the U.S. Department of Defense
  • Explain the relationship of the U.S. Global Positioning System with comparable systems sponsored by Russia and the European Union and the Global Navigation Satellite System
  • Discuss the role of GPS in location-based services (LBS)
  • Specify the features of a GPS receiver that is able to achieve geometric accuracies on the order of centimeters without post-processing
  • Explain the relevance of the concept of trilateration to both GPS positioning and control surveying
  • Perform differential correction of GPS data using reference data from a CORS station
  • List, define, and rank the sources of error associated with GPS positioning
  • Distinguish between horizontal and vertical accuracies when using coarse acquisition codes/standard positioning service (C-codes) and precision acquisition codes/precise positioning service (P-codes)
DC-19 - Ground verification and accuracy assessment
  • Evaluate the thematic accuracy of a given soils map
  • Explain how U.S. Geological Survey scientists and contractors assess the accuracy of the National Land Cover Dataset
DC-02 - Land records
  • Distinguish between GIS, LIS, and CAD/CAM in the context of land records management
  • Evaluate the difference in accuracy requirements for deeds systems versus registration systems
  • Exemplify and compare deed descriptions in terms of how accurately they convey the geometry of a parcel
  • Distinguish between topological fidelity and geometric accuracy in the context of a plat map
DC-15 - Mission planning
  • Plan an aerial imagery mission in response to a given request for proposals and map of a study area, taking into consideration vertical and horizontal control, atmospheric conditions, time of year, and time of day
DC-10 - Nature of aerial photograph data
  • Differentiate oblique and vertical aerial imagery
  • Describe the location and geometric characteristics of the “principal point” of an aerial image
  • Recognize the distortions and implications of relief displacement and radial distortion in an aerial image
  • Explain the phenomenon that is recorded in an aerial image
  • Compare and contrast digital and photographic imaging
  • Explain the significance of “bit depth” in aerial imaging
DC-16 - Nature of multispectral image data

A multispectral image comprises a set of co-registered images, each of which captures the spatially varying brightness of a scene in a specific spectral band, or electromagnetic wavelength region. An image is structured as a raster, or grid, of pixels. Multispectral images are used as a visual backdrop for other GIS layers, to provide information that is manually interpreted from images, or to generate automatically-derived thematic layers, for example through classification. The scale of multispectral images has spatial, spectral, radiometric and temporal components. Each component of scale has two aspects, extent (or coverage), and grain (or resolution). The brightness variations of an image are determined by factors that include (1) illumination variations and effects of the atmosphere, (2) spectral properties of materials in the scene (particularly reflectance, but also, depending on the wavelength, emittance), (3) spectral bands of the sensor, and (4) display options, such as the contrast stretch, which affect the visualization of the image. This topic review focuses primarily on optical remote sensing in the visible, near infrared and shortwave infrared parts of the electromagnetic spectrum, with an emphasis on satellite imagery.  

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