Midterm Study Powerpoint

Midterm Study Powerpoint - Data Collection Techniques...

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Unformatted text preview: Data Collection Techniques Raster Vector Primary Digital remote sensing images GPS measurements Digital aerial photographs Survey measurements Secondary Scanned maps Topographic surveys DEMs from maps Toponymy data sets from atlases Primary Data Capture Capture specifically for GIS use Raster remote sensing e.g. SPOT and IKONOS satellites and aerial photography Passive and active sensors Resolution is key consideration Three key aspects of resolution: Spatial Spectral Vector Primary Data Capture Surveying Locations of objects determines by angle and distance measurements from known locations Uses expensive field equipment and crews Most accurate method for large scale, small areas GPS Collection of satellites used to fix locations on Earths surface Differential GPS used to improve accuracy Secondary Geographic Data Capture Data collected for other purposes can be converted for use in GIS Raster conversion Scanning of maps, aerial photographs, documents, etc Important scanning parameters are spatial and spectral (bit depth) resolution Vector Secondary Data Capture Collection of vector objects from maps, photographs, plans, etc. Digitizing Manual (table) Heads-up and vectorization Photogrammetry the science and technology of making measurements from photographs, etc. COGO Coordinate Geometry Managing Data Capture Projects Key principles Clear plan, adequate resources, appropriate funding, and sufficient time Fundamental tradeoff between Quality, speed and price Two strategies Incremental Blitzkrieg (all at once) Alternative resource options In house Spet external agency Summary Data collection is very expensive, time- consuming, tedious and error prone Good procedures required for large scale collection projects Main techniques Primary Raster e.g. remote sensing Vector e.g. field survey Secondary Raster e.g. scanning Vector e.g. table digitizing Addendum: Volunteered Geographic Information (VGI) An unfortunate case study The Tea Fire Santa Barbara, California, Nov. 2008 Exacerbated by sundowner VGI: An unfortunate case study The Tea Fire Official sources: Precise fire boundaries every 24-36 hours GIS and Image-based techniques PDF format, posted online and distributed at community outlets Unofficial sources Rough boundaries Real-time Volunteered Geographic Information (VGI) @ GMU 30,000+ students Majority geo-aware and with mobile computing Could they be used to augment an official information source with VGI?...
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Midterm Study Powerpoint - Data Collection Techniques...

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