<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div dir="ltr">Thanks for sharing Christoph,</div><div dir="ltr"><br></div><div dir="ltr">It’s an interesting paper and I will read it more carefully. Another approach could be to make a point cloud with the drone images and to work with a high resolution DEMs. Depending in the drone camera and flight altitude, you could have a really good cm level DEM. That could help with both semi automatic classification methods, and deep learning. It could make it much easier also to identify cracks visually by building, for example, a shade model.</div><div dir="ltr"><br></div><div dir="ltr">The time spent doing this automatically is likely going to be bigger than the time spent doing it manually. It depends on the scale and goal of the project of course.</div><div dir="ltr"><br></div><div dir="ltr">You could always use the KISS method (Keep it simple stupid!) and just spray paint the cracks before flighting the drone. Depends on what you want to achieve.</div><div dir="ltr"><br></div><div dir="ltr">Cheers!</div><div dir="ltr"><br></div><div dir="ltr">Nicolas</div><div dir="ltr"><br></div><div dir="ltr"><br></div><div dir="ltr"><br><blockquote type="cite">Le 14 déc. 2019 à 13:57, Christoph Jung <jagodki.cj@gmail.com> a écrit :<br><br></blockquote></div><blockquote type="cite"><div dir="ltr">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"><div dir="ltr"><div dir="ltr">Hello Doug,</div><div dir="ltr"><br></div><div dir="ltr">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:</div><div dir="ltr"><br></div><div dir="ltr"><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></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 07:05 schrieb Doug <dougf.ccn@comcast.net>:<br><br></blockquote></div><blockquote type="cite"><div dir="ltr"><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">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.<o:p></o:p></span></p><p class="MsoNormal"><span style="font-family:"Arial",sans-serif"><o:p> </o:p></span></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?<o:p></o:p></span></p><p class="MsoNormal"><span style="font-family:"Arial",sans-serif"><o:p> </o:p></span></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?<o:p></o:p></span></p><p class="MsoNormal"><span style="font-family:"Arial",sans-serif"><o:p> </o:p></span></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.<o:p></o:p></span></p><p class="MsoNormal"><span style="font-family:"Arial",sans-serif"><o:p> </o:p></span></p><p class="MsoNormal"><span style="font-family:"Arial",sans-serif">Thanks.<o:p></o:p></span></p><p class="MsoNormal"><span style="font-family:"Arial",sans-serif">Doug<o:p></o:p></span></p><p class="MsoNormal"><span style="font-family:"Arial",sans-serif"><o:p> </o:p></span></p><p class="MsoNormal"><span style="font-family:"Arial",sans-serif"><o:p> </o:p></span></p></div><span>_______________________________________________</span><br><span>Qgis-user mailing list</span><br><span>Qgis-user@lists.osgeo.org</span><br><span>List info: https://lists.osgeo.org/mailman/listinfo/qgis-user</span><br><span>Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user</span></div></blockquote></div><span>_______________________________________________</span><br><span>Qgis-user mailing list</span><br><span>Qgis-user@lists.osgeo.org</span><br><span>List info: https://lists.osgeo.org/mailman/listinfo/qgis-user</span><br><span>Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user</span></div></blockquote></body></html>