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Published byLynette Rich Modified over 9 years ago
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Using GIS for Analysis: Queries Re-classification Map overlay Real world Land use Elevation Parcels Streets Retail A sample of approaches:
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Queries Aspatial Questions about attributes How many ___ are there? Which is the oldest? Which has the greatest land value? Could be answered with database software alone Spatial Questions about location, size, shape, distances, etc. Where is ___ ? Which is the longest US route within the county? Which is the most isolated golf course? Require a map – or GIS
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Combination Queries Some queries involve 2 or more criteria (spatial or aspatial) For these, use Boolean operators: AND, OR, NOT
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Combination Queries Which golf courses are in Mesa AND have 36 holes? In Mesa 36 holes
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Combination Queries Which golf courses are in Mesa OR have 36 holes? In Mesa 36 holes
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Combination Queries Which 36-hole golf courses are NOT in Mesa? In Mesa 36 holes
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Using GIS for Analysis Queries Re-classification Map overlay
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Reclassification Result of query is a new data layer Which land in Maricopa County is federally managed? BIA BLM BOR DOD FS FWS NPS
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Query approach: Which land is managed by BIA OR BLM OR BOR OR FS OR FWS OR NPS? BIA BLM BOR DOD FS FWS NPS
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Reclassification Approach: a New Data Layer Federally managed Other
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Reclassification approach cellOwnership A1BLM A2BLM A3FS A4Non-fed CellOwnership A1Fed A2Fed A3Fed A4Non-fed Reclassification is often a step to get data ready for overlay analysis Data Table Before Reclassification Data Table After Reclassification
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Using GIS for Analysis Queries Re-classification Map overlay
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Map Overlay Ian McHarg (“Design with Nature”) – pre-computer advocate of map overlay
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Map Overlay vs. Combination Query “Which Golf Courses are in Mesa AND have 36 holes?” Map overlay produces a new data layer
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Map Overlay vs. Reclassification Which land in Maricopa County is Federally managed? BIA BLM BOR DOD FS FWS NPS Map overlay involves data from two or more layers
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An example of a GIS analysis… GIS as a tool in fire management: Sequoia-Kings Canyon National Park
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GIS as a tool in fire management: Sequoia-Kings Canyon National Park Question: “Where should we do controlled burns, in order to best reduce the risk of severe out-of-control wildfires?” Several aspects to consider: Ecological need (natural fire interval) Human value: Infrastructure, human life & safety Hazard: ability to control a fire, once started Risk: based on historic record of wildfire occurrence
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Analysis to determine ecological need Data available: Vegetation ClassificationRI max 1 - Ponderosa Mixed Conifer6 2 - White Fir Mixed Conifer16 3 - Red Fir Mixed Conifer50 4 - Lodgepole Pine Forest163 5 - Xeric Pine Forest50 6 - Subalpine Conifer508 7 - Foothills Hardwood & Grassland17 8 - Foothills Chaparral60 Maximum average interval for fire occurrence 1.Natural Occurrence of fire, by species, based on analysis of tree rings
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Analysis to determine ecological need Data available: Ponderosa forest 2.Vegetation map
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Data available: Analysis to determine ecological need 3.Historical fires
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Analysis steps: Departure from natural fire interval Vegetation types Reclassify Overlay Fire return interval Date of last fire Reclassify Years since last fire FRI TSLF Analysis to determine ecological need
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Analysis steps: Departure from natural fire interval Reclassify Ecological need for burn Departure index Need to burn <-5Extreme -5 to -2High -2 to 0Moderate > 0Low Analysis to determine ecological need
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Map of ecological burn need
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Additional steps …. Where to do controlled burns Ecological burn need Ability to control burn Vegetation types Types of fuel slope elevation Date of last fire
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Where to do controlled burns Ecological burn need Ability to control burn Vegetation types Types of fuel slope elevation Date of last fire Infrastructure & Safety issues Risk of wildfire Additional steps ….
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Today’s Challenges Environmental, Social, Political, Economic … Local, National, Global Information is an essential tool to address these issues Geographic technology can help to answer more complex questions covering larger geographic extents than ever before
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Geographic information Involves a specification of location on the earth’s surface (WHERE) Also involves WHAT is at that location Goal is to uncover WHY something is located where it is
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