This data set contains the estimated Secchi depth (water clarity) measurements for 8645 Wisconsin lakes, derived from Landsat-5 and -7 satellite imagery acquired during the 1999-2001 time period. For details of the process used to create these data, see: Chipman, J. W., T. M. Lillesand, J. E. Schmaltz, J. E. Leale, and M. J. Nordheim. 2004. “Mapping Lake Water Clarity with Landsat Images in Wisconsin, USA.” Invited paper, Canadian Journal of Remote Sensing, Special Issue on Remote Sensing and Resource Management in Nearshore and Inland Waters, 30(1):1-7. Polygons for each lake were taken from the WDNR 1:24,000-scale Hydrography GIS data set (version 2). Several existing fields were deleted, and new ones were added.