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IKONOS Data for Water Quality Assessments

IKONOS data with four multispectral bands similar to Landsat TM bands 1-4 and high spatial resolution (4 m multispectral and 1 m panchromatic) is potentially well suited for assessment of small lakes. To explore the capabilities of IKONOS data for lake water quality assessment and monitoring, we acquired an August 23, 2000 IKONOS image for the City of Eagan, Minnesota. Eagan has 375 small lakes and ponds larger than one acre with 44-acre Thomas Lake being the largest. Click the pictures below to enlarge and view the resolution differences between Landsat and IKONOS images (Click your browsers back button to return to this page).

lexyankpan.jpg (103132 bytes)    lexyankmulti.jpg (94360 bytes)    lexyanklandsat.jpg (59825 bytes)

    

Lake signatures were extracted from 19 lakes that had SDT measurements within three days of the image date. A regression model was developed using the band 3:1 ratio and band 1 as the independent variables and the natural log of SDT as the dependent variable. The results were very similar to the results we have seen using Landsat data with an R2 = 0.82 and standard error of estimate (SEE) = 0.369. Click on this link to see a graph of IKONOS inferred TSI(SDT) vs. measured TSI(SDT). With the relationship we created a pixel level map of the water clarity of the small lakes and ponds in Eagan. Click on the picture below to enlarge the Eagan Water Clarity Map.

eagantsi2.jpg (256829 bytes)    

The use of IKONOS data for assessment of water clarity for small lakes at a city scale is promising. The high spatial resolution of the IKONOS data enables the assessment of smaller lakes and ponds than the Landsat 30-meter resolution allows. Only 14 of Eagan’s 375 ponds and lakes were included in our statewide assessment, while IKONOS data allows for the assessment of all of Eagan’s small lakes and ponds. IKONOS data also would be useful for detailed city land use/cover and wetland mapping. These maps could be used to assess how land use/cover affects water clarity. The cost of the IKONOS data would be prohibitively expensive for regional assessments, but would likely be affordable for many cities.

 

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Upper Great Lakes Regional Earth Science Applications Center
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