Presentation on theme: "Analysis of Water Clarity in Lake Superior using MODIS Images Yan Wang, Beth Peterson Forest Resources 3262 / 5262 Remote Sensing of Natural Resources."— Presentation transcript:
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
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.
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
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
Geometry correction, atmospheric correction : MRT tool ArcGIS: clip image and extract DN value of field samples from image Process field sample of turbidity
siteBand1Band3 (Band3-Band1) / (Band3+Band1fieldln(field) Chester Creek395172-0.393298060.84375-0.1699 Tischer Creek605370-0.2410256411.36250.309321 Kingsbury Creek532267-0.3316645815.5458331.713047 Miller Creek655304-0.3660062575.651.731656 Oliver Bridge - St Louis River661317-0.351738241100.37754.608938 WLSSD436322-0.1503957785.368751.680595 Y=ln(field) X=(B3-B1)/(B3+B1)
Month N equationR² June 24 y = 0.0041x - 0.2998R² = 0.0024 July 24 y = -0.0202x - 0.2635 R² = 0.3799 August 24 y = 0.006x - 0.2982R² = 0.0168 Sept 24 y = 0.0004x - 0.3366R² = 0.0002 Month N equation R² June 15 y = 9.2004x + 6.0675 R² = 0.1396 July 11 y = -11.955x - 0.7553 R² = 0.3609 August 10 y =- 50.181x - 12.919 R² = 0.76 September 6 y = -1.62x + 3.0091 R² = 0.1518 20112012
Site and Julian dateBand 1Band3 Regression Equation used Predicted Turbidity Actual Turbidity DE 185476252 y = -11.955x - 0.75532.9231615384.96 OS 185448241 y = -11.955x - 0.75542.8364053710.7 WE 185395188 y = -11.955x - 0.75553.4894427114 DE 193600391 y = -11.955x - 0.75561.7659865793.2 OS 193606407 y = -11.955x - 0.75571.5932143142.1 WE 193605393 y = -11.955x - 0.75581.7842390787.6 July 2012
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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