<div class="description">
Chiefly maps.; "GIS and cartography: Dean R. Martin; Graphic design &amp; layout: David S. Orr; Editing: Charles R. Salmons"--Page ii.; "This project was funded by the Great Lakes Geologic Mapping Coalition surficial mapping grant program"--Page iv.; Includes bibliographical references (page 9).; "A digital elevation model (DEM), generated from Light Distance and Ranging (LiDAR) data, was used to create a map layer that identified low, enclosed areas. To locate potential sinkholes, these low spots were cross referenced with known karst points from previous studies, bedrock geology, aerial photography of multiple sources and ages, soil maps, glacial drift thickness maps, and water well logs. ... Depressions were then visited in the field, evaluated, and photographed. Through this process some of the LiDAR-derived depressions were found not to be sinkholes. Features such as building foundations, broken field tiles, steep-walled streams, road culverts, and glacial features often produced enclosed areas similar in shape to sinkholes. Springs do not typically do not show up as depressions, and they were located during field work by spotting springhouses and flowing seeps. Field visits are important for confirming sinkhole sizes and depths as well. ..."--Pages 1-2.</div>
2017.
This file was contributed to Wikimedia Commons by <a href="https://en.wikipedia.org/wiki/en:State_Library_of_Ohio" class="extiw" title="w:en:State Library of Ohio"><span title="library">State Library of Ohio</span></a> as part of a cooperation project. The donation was facilitated by the <a href="https://en.wikipedia.org/wiki/Digital_Public_Library_of_America" class="extiw" title="w:Digital Public Library of America">Digital Public Library of America</a>, via its partner Ohio Digital Network.<span style="text-align:left">
<ul><li><a rel="nofollow" class="external text" href="http://www.ohiomemory.org/cdm/ref/collection/p267401ccp2/id/15459">Record in source catalog</a></li>
<li>DPLA identifier: <a rel="nofollow" class="external text" href="https://dp.la/item/614f4fd47fb10722b8fb90f387a5e9e6">614f4fd47fb10722b8fb90f387a5e9e6</a></li>
<li>State Library of Ohio identifier: <a rel="nofollow" class="external free" href="http://geosurvey.ohiodnr.gov/portals/geosurvey/PDFs/OpenFileReports/OFR_2017-2.pdf">http://geosurvey.ohiodnr.gov/portals/geosurvey/PDFs/OpenFileReports/OFR_2017-2.pdf</a>; 1004394763</li></ul></span>