Hi Michaël, do you mean the option Options>View/Edit>Prevent edits resulting invalid geometries?
I am not understanding this option. What is the use of drawing a selfintersection polygon? 1. In my opinion a program should never *compute* invalide geometries like multipolygon if it is not a valid multipolygon. 2. If a user construct an invalide geometry there must be a warning but it should not drawn. 2. The other side is to *load* invalide geometries from extern and have a chance to correct them. Is this option Options>View/Edit>Prevent edits resulting invalid geometries for this case? Uwe Am 10.04.2013 08:53, schrieb Michaël Michaud: > Hi Larry, > > Thanks for the input, > I followed your suggestion to add a warning in the status bar. > I did the test for the MultiPolygon case only though. > > Not sure it is useful in the general case. Maybe it would be > better to make the plugin consistent with the edit tools option > "accept invalid geometry". I think it is not yet. > > Michaël > >> Hi Michaël, >> >> Echoing what I think you are proposing: >> >> 1) when Combine Selected Features is invoked, a basic topology >> validity check is done on the result. >> >> 2) Any errors should be reported in the status bar or the Output Window. >> >> 3) If an invalid geometry results from building a MultiPolygon, a >> GeometryCollection is built instead. >> >> +1 if this is the plan. -1 if the plan is to just build a >> GeometryCollection instead. >> >> regards, >> >> Larry >> >> On Tue, Apr 9, 2013 at 1:36 PM, Michaël Michaud >> <michael.mich...@free.fr <mailto:michael.mich...@free.fr>> wrote: >> >> Hi, >> > Is it in OJ possible to check first for valid >> > geometries when >> > "Combine Selected Features" >> > or is this a great problem? >> > >> > If it is a great problem maybe it is better >> > "Combine Selected Features" >> > makes always a geometrycollection? >> There are several points : >> >> 1 - in the step by step process you described, error should >> have been thrown while combining the two polygons, not >> while moving the resulted invalid multipolygon >> >> 2 - I agree that in this case, building a valid GeometryCollection >> is better than building an invalid Multipolygon, even if >> GeometryCollection are much less useful (many operations >> accepting MultiPolygon will fail on GeometryCollection). >> If if no one has any objection, I propose to do the change. >> >> 3 - you surely knows that OpenJUMP has a hidden option to >> accept/refuse invalid geometries during edit operations (in >> this case, it is of no help though) >> >> Regards, >> >> Michaël >> > >> > What do you think? >> > >> > Regards >> > >> > Uwe >> > >> > Am 09.04.2013 03:21, schrieb Martin Davis: >> >> As Michael and Stefan point out, Polygons in a MultiPolygon must be >> >> edge-disjoint (which another way of stating the formal >> definition "must >> >> only touch at a finite number of points". If they touched along an >> >> edge, that would cause an infinite number of points to be >> coincident). >> >> >> >> Another way of looking at this is that MultiPolygons are in a >> sense the >> >> canonical description of a given area of the plane. If edge >> touches or >> >> overlaps were allowed then there would be an infinite number of >> >> geometries which described the same area. >> >> >> >> Also, from the point of view of computing polygon overlay and >> spatial >> >> relationships this is a nice rule to have, since it reduces the >> number >> >> of cases which need to be checked for. This makes the code >> simpler and >> >> more performant. The cost is that it is necessary to ensure that >> >> MultiPolygons are valid at creation time. This is a reasonable >> >> tradeoff, since in general geometries are queried more often >> than they >> >> are created. >> >> >> >> GeometryCollections on the other hand have no particular >> semantics - >> >> they are just "bags" of geometries. This makes them useful for >> holding >> >> arbitrary sets of geometries, but makes them more complex (and >> sometimes >> >> slower) to process. >> >> >> >> On 4/8/2013 11:04 AM, Michaël Michaud wrote: >> >>> Hi Uwe, Stefan, >> >>> >> >>> OpenJUMP (JTS) is right, this MultiPolygon is not OGC conform >> >>> >> >>> Here is the citation : >> >>> Multipolygon >> >>> 2. The Boundaries of any 2 Polygons that are elements of a >> MultiPolygon >> >>> may not ‘cross’ and may touch >> >>> at only a finite number of points. (Note that crossing is >> prevented by >> >>> assertion 1 above). >> >>> >> >>> Don't ask me why, I've always thought it is strange that lines can >> >>> share their boundaries in a MultiLineString and polygons cannot >> >>> share an edge in a MultiPolygon, but it's a well established rule >> >>> that JTS follows. >> >>> >> >>> Michaël >> >>> >> >>> >> >>>> Hi Uwe, >> >>>> >> >>>> I am not sure I would call it a bug. OJ, should (try to) >> create data >> >>>> that are OGC conform, but in this case it doesn't. Which >> means, the >> >>>> case >> >>>> needs special treatment, but this is not implemented. >> >>>> >> >>>> That the multi-polygon causes an error is with the OGS SF >> >>>> specification >> >>>> = correct. However, that the geometry collection does not >> cause an >> >>>> error >> >>>> should be correct aw well, because there is, I believe, >> nothing said >> >>>> about geometry collections and their validity. Geometry >> collections >> >>>> should be allowed to have any type of geometries in what ever >> way they >> >>>> are drawn - like a "container". If we would check geometry >> collections >> >>>> for their validity it may be that people cannot store anymore >> the data >> >>>> they have. Hence, checking should be optional. >> >>>> >> >>>> But I guess here, Michael M. knows probably more about OGC >> >>>> conformance? >> >>>> I'll also cc to JTS list. >> >>>> >> >>>> cheers, >> >>>> stefan >> >>>> >> >>>> PS: the Multi-polygon: >> >>>> >> >>>> MULTIPOLYGON ((( >> >>>> 80 125, >> >>>> 80 241, >> >>>> 175 241, >> >>>> 175 125, >> >>>> 80 125 >> >>>> )), (( >> >>>> 175 125, >> >>>> 175 241, >> >>>> 263 241, >> >>>> 263 125, >> >>>> 175 125 >> >>>> ))) >> >>>> >> >>>> Am 08.04.13 09:48, schrieb Uwe Dalluege: >> >>>>> Hi Stefan, >> >>>>> >> >>>>> I am afraid I do not understand :-( >> >>>>> Do you think this is a bug in OJ? >> >>>>> The multipolygon causes an error >> >>>>> the geometrycollection not. >> >>>>> >> >>>>> Is this behaviour OGC-conform (simpel features...)? >> >>>>> What do you think? >> >>>>> >> >>>>> uwe >> >>>>> >> >>>>> Am 08.04.2013 16:36, schrieb Stefan Steiniger: >> >>>>>> Hi, >> >>>>>> >> >>>>>> so - well the situation is not so nice, as it should be valid. >> >>>>>> However, >> >>>>>> the JTS TestBuilder says the Multi-Polgyon is invalid >> because of >> >>>>>> "Self-intersection at or near point (175.0, 125.0, NaN)" >> >>>>>> >> >>>>>> Same message appears when you try to add it as a new feature. >> >>>>>> >> >>>>>> maybe you can make it valid before by running a zero-buffer >> over it? >> >>>>>> >> >>>>>> stefan >> >>>>>> >> >>>>>> Am 08.04.13 07:30, schrieb Uwe Dalluege: >> >>>>>>> Hi, >> >>>>>>> >> >>>>>>> if you put a third geometrie to the two polygons, >> >>>>>>> for instance a linestring, and combine them >> >>>>>>> you will receive a geometrycollection >> >>>>>>> and not a multipolygon. >> >>>>>>> >> >>>>>>> The geometrycollection causes *no* errors >> >>>>>>> but the multipolygon. >> >>>>>>> >> >>>>>>> Uwe >> >>>>>>> >> >>>>>>> >> >>>>>>> Am 08.04.2013 12:05, schrieb Uwe Dalluege: >> >>>>>>>> Hi, >> >>>>>>>> >> >>>>>>>> I get the error: >> >>>>>>>> >> >>>>>>>> "The new geometry is invalid. Cancelled." >> >>>>>>>> and I am not shure whether this error is correct. >> >>>>>>>> >> >>>>>>>> 1. Switch "Snap to vertices" option. >> >>>>>>>> >> >>>>>>>> 2. Draw a rectangle. >> >>>>>>>> >> >>>>>>>> 3. Draw a second rectangle with two identical >> >>>>>>>> vertices from the first rectangle (with snap). >> >>>>>>>> >> >>>>>>>> 4. Select the two rectangles and >> >>>>>>>> "Combine Selected features" >> >>>>>>>> >> >>>>>>>> 5. Try to move this multipolygon with >> >>>>>>>> "Move Selected Items Tool". >> >>>>>>>> >> >>>>>>>> 6. The error appears >> >>>>>>>> "The new geometry is invalid. Cancelled." >> >>>>>>>> >> >>>>>>>> 7. The QA>Validate Selected Layers... >> >>>>>>>> causes a self-intersection in *one* point. >> >>>>>>>> >> >>>>>>>> Is this a bug in OJ (a precision-problem) >> >>>>>>>> or is the new geometry really invalide? >> >>>>>>>> >> >>>>>>>> Uwe >> >>>>>>>> >> >>>>>>>> >> >> ------------------------------------------------------------------------------ >> >>>>>>>> >> >>>>>>>> >> > >> > >> >> >> >> ------------------------------------------------------------------------------ >> Precog is a next-generation analytics platform capable of advanced >> analytics on semi-structured data. The platform includes APIs for >> building >> apps and a phenomenal toolset for data science. Developers can use >> our toolset for easy data analysis & visualization. Get a free >> account! >> http://www2.precog.com/precogplatform/slashdotnewsletter >> _______________________________________________ >> Jump-pilot-devel mailing list >> Jump-pilot-devel@lists.sourceforge.net >> <mailto:Jump-pilot-devel@lists.sourceforge.net> >> https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel >> >> >> >> >> ------------------------------------------------------------------------------ >> Precog is a next-generation analytics platform capable of advanced >> analytics on semi-structured data. The platform includes APIs for building >> apps and a phenomenal toolset for data science. Developers can use >> our toolset for easy data analysis & visualization. Get a free account! >> http://www2.precog.com/precogplatform/slashdotnewsletter >> >> >> _______________________________________________ >> Jump-pilot-devel mailing list >> Jump-pilot-devel@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel > > > > ------------------------------------------------------------------------------ > Precog is a next-generation analytics platform capable of advanced > analytics on semi-structured data. The platform includes APIs for building > apps and a phenomenal toolset for data science. Developers can use > our toolset for easy data analysis & visualization. Get a free account! > http://www2.precog.com/precogplatform/slashdotnewsletter > > > > _______________________________________________ > Jump-pilot-devel mailing list > Jump-pilot-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel > ------------------------------------------------------------------------------ Precog is a next-generation analytics platform capable of advanced analytics on semi-structured data. The platform includes APIs for building apps and a phenomenal toolset for data science. Developers can use our toolset for easy data analysis & visualization. Get a free account! http://www2.precog.com/precogplatform/slashdotnewsletter _______________________________________________ Jump-pilot-devel mailing list Jump-pilot-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel
