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UNC-Chapel Hill GEOG 070 - Sources of Geographic Information

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Sources of Geographic InformationTwo Types of Remote SensingPassive vs. Active Remote SensingRADAR Remote SensingRADAR Remote SensingRADAR Remote SensingSRTM MissionImprovement Over Old Global DEMsImprovement Over Old Global DEMsNexrad Doppler Weather RADARNexrad Doppler Weather RADARNexrad Doppler Weather RADARNexrad Coordinate SystemsNexrad Coordinate SystemsCONUS Hourly Nexrad RainfallDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005•Data properties: Spatial data, i.e. data that are associated with geographic locations•Data format: digital (analog data for traditional paper maps)•Data Inputs:•sampled from the real world•digitizing from paper maps•produced by government agencies, e.g. census bureau, USGS, USFS, state government, etc.•space or airborne remote sensing(NASA, NOAA, commercial, etc.)Approximately 80% of the duration of many large scale GIS projects is concerned with data input and managementSources of Geographic InformationDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005• Based on the source of the energy, remote sensing can be broken into two categories:• Passive remote sensing: The source of energy collected by sensors is either reflected solar radiation (e.g. cameras) or emitted by the targets(thermal imaging).• Active remote sensing: The source of energy collected by sensors is actively generated by a man-made device. Examples include RADAR (RAdio Detection And Ranging, which uses microwave energy) and LIDAR (LIght Detection Imagery And Ranging, which uses a laser).Two Types of Remote SensingDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005Passive vs. Active Remote SensingPassive sensors receive solar energy reflected by the Earth’s surface (2), along with energy emitted by the atmosphere (1), surface (3) and sub-surface (4)Active sensors receive energy reflected from the Earth’s surface that originally came from an emitter other than the Sunhttp://www.ccrs.nrcan.gc.ca/ccrs/learn/tutorials/fundam/chapter3/chapter3_1_e.htmlDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005•Remote sensing using RADAR can be active or passive:•Some earth materials do emit radiation in the microwave range of wavelengths (anywhere from a millimeter to a meter), and these can be sensed by a detector that operates just as many that we have already looked at does, sensing the energy passively•However today we’re primarily going to look at active RADAR remote sensing, where the source of the microwave energy which returns to the sensor is a man-made source or emitter, and the characteristics of the emitter and sensor are both selected for the particular application (i.e. choose the wavelength and other factors based on what you want to capture in the imagery)RADAR Remote SensingDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005•The platform/position of the emitter and sensor can vary:•Aircraft and ships are routinely fitted with active RADAR systems for purposes of navigation, although we find research and geographic information oriented systems on these platforms as well•There are satellite systems that use active microwave sensing systems (e.g. Radarsat, Japan’s Earth Resources Satellite JERS-1, and the SIR-C/X-SAR system that was flown on the space shuttle 1994 and again in 2000 -SRTM)•There are land-based systems like the Doppler RADAR network used to produce precipitation estimates (i.e. WRAL News’ weather imagery)RADAR Remote SensingDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005•The following slides were produced by the Canadian Center for Remote Sensing, a division of Natural Resources Canada•Canada has been a leader in satellite RADAR remote sensing through its Radarsat program, and has a very comprehensive educational package at:http://www.ccrs.nrcan.gc.ca/ccrs/learn/tutorials/gsarcd/downld_e.html(this is linked from the course website) which has information that covers just about anything that you might want to know about satellite RADAR remote sensingRADAR Remote SensingDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005David Tenenbaum – GEOG 070 – UNC-CH Spring 2005David Tenenbaum – GEOG 070 – UNC-CH Spring 2005David Tenenbaum – GEOG 070 – UNC-CH Spring 2005David Tenenbaum – GEOG 070 – UNC-CH Spring 2005David Tenenbaum – GEOG 070 – UNC-CH Spring 2005David Tenenbaum – GEOG 070 – UNC-CH Spring 2005David Tenenbaum – GEOG 070 – UNC-CH Spring 2005David Tenenbaum – GEOG 070 – UNC-CH Spring 2005David Tenenbaum – GEOG 070 – UNC-CH Spring 2005David Tenenbaum – GEOG 070 – UNC-CH Spring 2005David Tenenbaum – GEOG 070 – UNC-CH Spring 2005David Tenenbaum – GEOG 070 – UNC-CH Spring 2005David Tenenbaum – GEOG 070 – UNC-CH Spring 2005David Tenenbaum – GEOG 070 – UNC-CH Spring 2005David Tenenbaum – GEOG 070 – UNC-CH Spring 2005David Tenenbaum – GEOG 070 – UNC-CH Spring 2005David Tenenbaum – GEOG 070 – UNC-CH Spring 2005David Tenenbaum – GEOG 070 – UNC-CH Spring 2005David Tenenbaum – GEOG 070 – UNC-CH Spring 2005David Tenenbaum – GEOG 070 – UNC-CH Spring 2005David Tenenbaum – GEOG 070 – UNC-CH Spring 2005David Tenenbaum – GEOG 070 – UNC-CH Spring 2005SRTM Mission• Purpose: To produce a digital elevation model of most the land surface of the Earth (80% of it, located between 60 degrees N and 56 degrees S)• The DEM has a high horizontal spatial resolutionof about 1 arc-second (~30m pixels) with a less impressive vertical resolution of +/- 16m elevation at 90% confidence• While the vertical resolution is not that high, this is a big improvement in data for much of the Earth that has never been mapped at a high resolution before, and at least the vertical error is consistent, because the data comes from a single sourceDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005Improvement Over Old Global DEMshttp://srtm.usgs.gov/Mission/srtmcomparison221kb.htmlDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005Improvement Over Old Global DEMsLake Balbina, near Manaus, Brazil as depicted using old global 1km data (on the left), and the SRTM 30m DEM (on the right)http://srtm.usgs.gov/srtmimagegallery/Lake%20Balbina,%20near%20Manaus,%20Brazil.htmDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005Nexrad Doppler Weather RADAR•The Nexrad network of weather RADAR sensors consists of 158 radars that each have a maximum range of 250 miles that together provide excellent coverage of the continental United StatesThe sensors are known by the designation


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