Sorry, I have not got any example dataset. If some one can create a schematic/mock-up data set, we can test our way forward.
I am looking into the fundamentals of data testing and quality assurance techniques by using PostGIS. Regards, David On Mon, 2 May 2022 at 19:57, Martin Davis <[email protected]> wrote: > Yes, that technique only applies to polygonal coverages. > > Your use case is not clear to me. An example dataset might make that more > clear. > > On Mon, May 2, 2022 at 11:40 AM Shaozhong SHI <[email protected]> > wrote: > >> >> >> On Mon, 2 May 2022 at 19:05, Martin Davis <[email protected]> wrote: >> >>> That blog post does provide useful queries for finding polygon overlaps >>> and gaps. >>> >>> Overlaps are found via testing if polygon interiors intersect, using the >>> DE-9IM relate mask 2********. >>> >>> Gaps are found by identifying holes in the union of the set of >>> polygons. One issue with this is that computing the union of large >>> datasets can be slow. Lars' solution provides some ideas for dealing with >>> this. >>> >>> >>> I think that matters are rather more complex than this. >> >> For instance, I found 2 lines meet with each other at both ends. In this >> case, 2 intersections are both a point. One will find two lines form an >> enclosed area. >> >> When 2 lines intersect or meet/touch more than 2 times, intersection will >> return more than 2 points. For instance, when two lines meet at 3 points, >> one would get 2 gap polygons. >> >> Given 2 zigzagging lines, how to write a function to return overlaps and >> gaps is an interesting matter. >> >> Regards, >> >> David >> >> _______________________________________________ >> postgis-users mailing list >> [email protected] >> https://lists.osgeo.org/mailman/listinfo/postgis-users >> > _______________________________________________ > postgis-users mailing list > [email protected] > https://lists.osgeo.org/mailman/listinfo/postgis-users >
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