Hi Doug, This makes it a lot easier, the others mentioned good possibilities to find the cracks.
Concerning your question of segmentation of the roadbed: 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. Sincerely, Christoph > Am 14.12.2019 um 22:16 schrieb Doug <[email protected]>: > > > Christoph, > 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? > 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? > Doug > > From: Christoph Jung <[email protected]> > Sent: Saturday, December 14, 2019 11:57 AM > To: Doug <[email protected]> > Cc: [email protected] > Subject: Re: [Qgis-user] Record the cracks in our (private) streets > > Hello Doug, > > 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: > > https://www.tu-ilmenau.de/fileadmin/media/neurob/publications/conferences_nat/2017/Eisenbach-ATIM-2017.pdf > > Sincerely, > Christoph > > > Am 14.12.2019 um 07:05 schrieb Doug <[email protected]>: > > > 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. > > 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? > > 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? > > 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. > > Thanks. > Doug > > > _______________________________________________ > Qgis-user mailing list > [email protected] > List info: https://lists.osgeo.org/mailman/listinfo/qgis-user > Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
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