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Published byErin Cole Modified over 8 years ago
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By: Reid Swanson Sam Soper
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Goal: To describe land cover/use changes that have occurred in the Twin Cities Metro-Area from the 1991 to 2005 Quantifying the increase in impervious surface Applications for which this type of study would be useful:
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Data Rectification Classification Change Detection Accuracy
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Data Classification image: Multispectral image provided by Joe Knight Reference images: 1991: Most of the state was flown in spring of 1991; the remainder was completed spring 1992. Photos are available in both color-infrared and black-and-white; the latter were used to produce statewide digital orthophotos The original images from both flights are 9" x 9" and cover about 25 square miles at an approximate scale of 1:40,000
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Data Reference images: 2005: a 2006 image taking in Summer - Fall MDA natural color 1-meter USGS procured photos from MDA for public distribution. Twin Cities 2006 Spring USGS natural color 0.3-meter Minneapolis - St. Paul area
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1991
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2005
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Rectification Regular linear features (ex. Roads) lined up GOOD Area did not match up Subset Image Some atmospheric interference creation an unclassified class
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1991-No Subset
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1991-Subset
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2005- No Subset
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2005-Subset
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Cloud Interference
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Classification Unsupervised classification Maximum likelihood-(grouping pixels to nearest class mean) 20 spectral responses Need more variation between classes 40 spectral responses Recoded into 7 distinct classes Classes: Urban Forest Green Space Agriculture Water Wetland Unclassified
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Classification PROBLEM recode needs to work Couldn’t run thematic change detection Need same # of classes Output results wouldn’t have been clear Addition problems with accuracy assessment
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Change Detection Plan: Thematic Change Detection Results in “from-to” change Actual: Manual interpretation of histogram values Digital number comparison Allows us to see the magnitude of change, but not “from-to”
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Change Detection
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Change
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Accuracy Assessment Reference data : 1991: Most of the state was flown in spring of 1991; the remainder was completed spring 1992. Photos are available in both color-infrared and black-and-white; the latter were used to produce statewide digital orthophotos The original images from both flights are 9" x 9" and cover about 25 square miles at an approximate scale of 1:40,000 2005: a 2006 image taking in Summer - Fall MDA natural color 1-meter USGS procured photos from MDA for public distribution. Twin Cities 2006 Spring USGS natural color 0.3-meter Minneapolis - St. Paul area
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Accuracy Assessment Generated X,Y coordinates in ERDAS Sampling method: Simple random Exported to ARCMAP MANUAL MANIPULATION OF ACCURACY DUE TO RECODE FAILURE Allowed ourselves to see classification data Compared classified to reference data Error Matrix(by hand!)
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Reference Points- State layer
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Reference Points- City layer
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Error Matrix 1991
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Error Matrix 2005
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Minimum Mapping Unit 30 meters
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Applications: Change in impervious surface (urban areas) and its impacts on water quality Identifying areas of population increases examine commuter effect on carbon emissions
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Water Quality
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Woodbury, MN
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Conclusion Despite program errors our data allows us to see the change in cover type as a result of population growth and human expansion 198 more km^2 of urban area in 2005 This information can useful in application to a variety of studies
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Thanks!!!!!
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