<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div dir="ltr">Hi Doug,</div><div dir="ltr"><br></div><div dir="ltr">This makes it a lot easier, the others mentioned good possibilities to find the cracks. </div><div dir="ltr"><br></div><div dir="ltr">Concerning your question of segmentation of the roadbed:</div><div dir="ltr">You could create a regular grid and count, measure or what else the cracks within the grid cells/polygons. A comparison based on this grid would be easy stuff. </div><div dir="ltr"><br></div><div dir="ltr">Sincerely,</div><div dir="ltr">Christoph</div><div dir="ltr"><br><blockquote type="cite">Am 14.12.2019 um 22:16 schrieb Doug <dougf.ccn@comcast.net>:<br><br></blockquote></div><blockquote type="cite"><div dir="ltr"><meta http-equiv="Content-Type" content="text/html; charset=utf-8"><meta name="Generator" content="Microsoft Word 15 (filtered medium)"><style><!--
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</o:shapelayout></xml><![endif]--><div class="WordSection1"><p class="MsoNormal"><span style="font-family:"Arial",sans-serif;color:blue">Christoph,<o:p></o:p></span></p><p class="MsoNormal"><span style="font-family:"Arial",sans-serif;color:blue">Thanks for the reference. The crack detection capability they describe is far beyond what I want. All the cracks in our streets were cleaned and filled with crack-sealant (tar) before I got my photos. So the crack lines stand out in stark contrast to the road bed. I think photoshop and other tools can use extreme contrasting to generate outlines. That’s what I was thinking of. Does such a filter plugin exist in CGIS? If not, can I code one?<o:p></o:p></span></p><p class="MsoNormal"><span style="font-family:"Arial",sans-serif;color:blue">The other parts of my problem still exist: defining segments of the roadbed, and relating the crack to the segments. Do you have any ideas how to do that?<o:p></o:p></span></p><p class="MsoNormal"><span style="font-family:"Arial",sans-serif;color:blue">Doug<o:p></o:p></span></p><p class="MsoNormal"><span style="font-family:"Arial",sans-serif;color:blue"><o:p> </o:p></span></p><div style="border:none;border-left:solid blue 1.5pt;padding:0in 0in 0in 4.0pt"><div><div style="border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in"><p class="MsoNormal"><b>From:</b> Christoph Jung <jagodki.cj@gmail.com> <br><b>Sent:</b> Saturday, December 14, 2019 11:57 AM<br><b>To:</b> Doug <dougf.ccn@comcast.net><br><b>Cc:</b> qgis-user@lists.osgeo.org<br><b>Subject:</b> Re: [Qgis-user] Record the cracks in our (private) streets<o:p></o:p></p></div></div><p class="MsoNormal"><o:p> </o:p></p><div><div><p class="MsoNormal">Hello Doug,<span style="font-size:12.0pt"><o:p></o:p></span></p></div><div><p class="MsoNormal"><o:p> </o:p></p></div><div><p class="MsoNormal">Automatic crack detection is not an easy problem. A semi automatic classification will not find all cracks, because cracks can have very different appearances. A state of the art approach would be deep learning. At the German university TU Ilmenau they developed a robust neuronal network for the detection and classification of distresses in road surfaces. Here is a Link to one of the papers of this project:<o:p></o:p></p></div><div><p class="MsoNormal"><o:p> </o:p></p></div><div><p class="MsoNormal"><a href="https://www.tu-ilmenau.de/fileadmin/media/neurob/publications/conferences_nat/2017/Eisenbach-ATIM-2017.pdf">https://www.tu-ilmenau.de/fileadmin/media/neurob/publications/conferences_nat/2017/Eisenbach-ATIM-2017.pdf</a><o:p></o:p></p></div><div><p class="MsoNormal"><o:p> </o:p></p></div><div><p class="MsoNormal">Sincerely,<o:p></o:p></p></div><div><p class="MsoNormal">Christoph<o:p></o:p></p></div><div><p class="MsoNormal"><br><br><o:p></o:p></p><blockquote style="margin-top:5.0pt;margin-bottom:5.0pt"><p class="MsoNormal" style="margin-bottom:12.0pt">Am 14.12.2019 um 07:05 schrieb Doug <<a href="mailto:dougf.ccn@comcast.net">dougf.ccn@comcast.net</a>>:<o:p></o:p></p></blockquote></div><blockquote style="margin-top:5.0pt;margin-bottom:5.0pt"><div><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman",serif"><o:p></o:p></span></p><p class="MsoNormal"><span style="font-family:"Arial",sans-serif">I have imported a set of drone pictures to QGIS. They show the streets in my subdivision. I want to “record” the cracks in the pavement to be able to compare them over time. I want to be able to segment the streets in arbitrary lengths. For each segment, I want to “draw” the cracks (in layers) to record where they are. Every year or two I will repeat the process. The purpose is to be able to compare the set of cracks in successive snapshots to see how the asphalt is holding up and identify underlying problems. I would love to have some software to find the cracks for me and generate the crack layer, if anyone knows of such software.</span><o:p></o:p></p><p class="MsoNormal"><span style="font-family:"Arial",sans-serif"> </span><o:p></o:p></p><p class="MsoNormal"><span style="font-family:"Arial",sans-serif">First problem: I can trace the outline of the streets to generate a layer which represents to road surface. Is there a way to slice that layer by picking two points to “slice” the layer and then have two layers? And then repeat the process so that I get the segments that I want? Alternatively, is there a way to create a segment and “snap” to next segment so there is not overlap or missing space?</span><o:p></o:p></p><p class="MsoNormal"><span style="font-family:"Arial",sans-serif"> </span><o:p></o:p></p><p class="MsoNormal"><span style="font-family:"Arial",sans-serif">Second problem. Given that I have a layer representing a segment of the road surface, can I “draw” the cracks for that segment such that every line in the cracks layer is related (as in SQL) to the segment it reside in?</span><o:p></o:p></p><p class="MsoNormal"><span style="font-family:"Arial",sans-serif"> </span><o:p></o:p></p><p class="MsoNormal"><span style="font-family:"Arial",sans-serif">Once I have the road surface segments, and the associated cracks, I can then use SQL to generate all sorts of reports on the cracks: average and median length, number of horizontal and vertical cracks, total crack length per road surface segment (or square feet), etc.</span><o:p></o:p></p><p class="MsoNormal"><span style="font-family:"Arial",sans-serif"> </span><o:p></o:p></p><p class="MsoNormal"><span style="font-family:"Arial",sans-serif">Thanks.</span><o:p></o:p></p><p class="MsoNormal"><span style="font-family:"Arial",sans-serif">Doug</span><o:p></o:p></p><p class="MsoNormal"><span style="font-family:"Arial",sans-serif"> </span><o:p></o:p></p><p class="MsoNormal"><span style="font-family:"Arial",sans-serif"> </span><o:p></o:p></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman",serif">_______________________________________________<br>Qgis-user mailing list<br><a href="mailto:Qgis-user@lists.osgeo.org">Qgis-user@lists.osgeo.org</a><br>List info: <a href="https://lists.osgeo.org/mailman/listinfo/qgis-user">https://lists.osgeo.org/mailman/listinfo/qgis-user</a><br>Unsubscribe: <a href="https://lists.osgeo.org/mailman/listinfo/qgis-user">https://lists.osgeo.org/mailman/listinfo/qgis-user</a><o:p></o:p></span></p></div></blockquote></div></div></div></div></blockquote></body></html>