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Analysis of Water Clarity in Lake Superior using MODIS Images Yan Wang, Beth Peterson Forest Resources 3262 / 5262 Remote Sensing of Natural Resources and Environment 12/10/12

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Analyze water quality in Lake Superior near Duluth 2011 and 2012 June – September Evaluate the effectiveness of MODIS data for determining water clarity Evaluate the compatibility of MODIS data with field data from streams.

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Satellite Aqua (as opposed to Tera) ~18:50 passover time Product: MDY09A1 bands 1–7 500m resolution 8 day composite (reduce cloud cover) Use bands 1 and 3 (red and blue) 8 images per month (4 in each band) Extracted: DN of the point at each site where field data was collected

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Turbidity Recorded as Nephelometric Turbidity Units (NTU) Turbidity data from Lake Superior Streams ~7 streams (depending on availability) Data recorded ~every 15 minuites Latitude and Longitude for each site Extracted: average of data collected at 18:30, 18:45, 18:90 for all 8 days of each image

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Geometry correction, atmospheric correction : MRT tool ArcGIS: clip image and extract DN value of field samples from image Process field sample of turbidity

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siteBand1Band3 (Band3-Band1) / (Band3+Band1fieldln(field) Chester Creek Tischer Creek Kingsbury Creek Miller Creek Oliver Bridge - St Louis River WLSSD Y=ln(field) X=(B3-B1)/(B3+B1)

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Month N equationR² June 24 y = x R² = July 24 y = x R² = August 24 y = 0.006x R² = Sept 24 y = x R² = Month N equation R² June 15 y = x R² = July 11 y = x R² = August 10 y = x R² = 0.76 September 6 y = -1.62x R² =

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June July August September

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JuneJuly August September

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Site and Julian dateBand 1Band3 Regression Equation used Predicted Turbidity Actual Turbidity DE y = x OS y = x WE y = x DE y = x OS y = x WE y = x July 2012

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Regression analysis produced very poor results. Streams were too small in comparison to MODIS pixels Missing or inaccurate turbidity data Turbidity values near the shore were different than values for the center of the lake. Much more variability in 2012, possibly as a result of the large flood that occurred early in the year

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