[postgis-users] TopologyException: geom is invalid
Roxanne Reid-Bennett
rox at tara-lu.com
Thu Feb 26 13:51:18 PST 2015
On 2/26/2015 4:08 PM, Joseph Spenner wrote:
> Roxanne:
> I think you're on to something here. I just did more tests, and
> found the following:
>
> This command fails with the error:
>
> select ST_Asgeojson( geom ) from dynamic.polys where
> ST_Intersects(ST_GeomFromGeoJSON('$jsonPoly'), geom)=TRUE and
> ST_Area(ST_Intersection(ST_GeomFromGeoJSON('$jsonPoly')::geography,
> geom::geography))>500
>
> == ERROR==
> DBD::Pg::st execute failed: ERROR: Error performing intersection:
> TopologyException: Input geom 0 is invalid: Self-intersection at or
> near point 1543100.5176146738 389360.239110158 at 1543100.5176146738
> 389360.239110158 at ./foo.pl line 50.
> DBD::Pg::st execute failed: ERROR: Error performing intersection:
> TopologyException: Input geom 0 is invalid: Self-intersection at or
> near point 1543100.5176146738 389360.239110158 at 1543100.5176146738
> 389360.239110158 at ./foo.pl line 50.
> == /ERROR==
>
>
> But this command succeeds, no error:
>
> select ST_Asgeojson( geom ) from dynamic.polys where
> ST_Intersects(ST_GeomFromGeoJSON('$jsonPoly'), geom)=TRUE
>
>
> The only thing different is the extra AND:
> ST_Area(ST_Intersection(ST_GeomFromGeoJSON('$jsonPoly')::geography,
> geom::geography))>500
>
> The reason I did this was to prevent false positives for geoms which
> were simply tangent, or "touching".
> For example, if I searched for MN, and there was poly/county on the
> northern IA border, it would be returned.
I haven't played with geography much as a data type, ymmv
Try casting the St_Intersection back to geometry and do an
ST_IsValidReason (and ST_GeometryType) on
ST_Intersection(ST_GeomFromGeoJSON('$jsonPoly')::geography, geom::geography)
or change the order on the cast to (**with correct SRIDs):
ST_Intersection(ST_GeomFromGeoJSON('$jsonPoly'), geom)::geography
and see what it says. You may be able to test for a non-polygon
(ST_Area of a (multi)linestring or (multi)point makes no sense) and/or
add ST_MakeValid around it. [not saying that is the problem - it just
might be tho]
>
> Looks like I need to find a better way to deal with the geoms that
> just touch with a single point or line in common.
Not necessarily - just a more robust way of testing edge use cases.
and/or maybe...
is not ST_Touches (for boundary only intersections)
and is { ST_Crosses (some but not all interior points in common) or
ST_Contains(one is wholly contained in the other) }
and then test ST_Area... essentially filtering out the edge cases before
Area is taken.
and again - the specific fix is dependent upon the specific cause.
>
> Any idea on a better way to handle this?
>
> Thanks for your help! I owe you a beer. :)
mmm beer
>
>
>
> ------------------------------------------------------------------------
> *From:* Roxanne Reid-Bennett <rox at tara-lu.com>
> *To:* postgis-users at lists.osgeo.org
> *Sent:* Thursday, February 26, 2015 1:16 PM
> *Subject:* Re: [postgis-users] TopologyException: geom is invalid
>
> On 2/26/2015 1:40 PM, Joseph Spenner wrote:
>> I ran the following against all 4 of my GeoJSON files:
>>
>> SELECT ST_IsSimple(ST_GeomFromGeoJSON('@poly'))
>> SELECT ST_IsValid(ST_GeomFromGeoJSON('@poly'))
>> SELECT ST_IsValidDetail(ST_GeomFromGeoJSON('@poly'))
>> SELECT ST_IsValidReason(ST_GeomFromGeoJSON('@poly'))
>>
>> where @poly contained each one of the following:
>>
>> http://microflush.org/stuff/json/MN.json
>> http://microflush.org/stuff/json/mnz091.json
>>
>> http://microflush.org/stuff/json/CA.json
>> http://microflush.org/stuff/json/nwsZone.json
>>
>>
>> The select returned no error. I tried to vary the input slightly to
>> make sure I was using the proper syntax, and was able to get errors--
>> such as:
>>
>> DBD::Pg::st execute failed: ERROR: geometry contains non-closed rings
>>
>> So, it would seem my geoms are ok.
>>
>> I've not yet tried the "ST_MakeValid". But wouldn't the above
>> indicate they're already valid?
>
> Yes ST_IsValid coming back true means that the geometry is "valid".
> (Topology Exceptions are most often thrown during operations on
> invalid geometries - so this test is the first that should be done
> when one occurs... in almost all cases)
>
> In my (limited) experience - just because 2 geometries are valid,
> doesn't mean that operations on them won't generate issues.
>
> Is it the cast to Geography, ST_Intersection or the ST_Area on the
> ST_Intersection that is throwing the error?
> My guess is going to be the ST_Area on the results of the ST_Intersection.
>
> So, is the result of the ST_Intersection of the two geographies valid?
>
> Have you perhaps looked at all the involved geometries (since you are
> down to 4) at the point identified by the original Topo error in
> order to understand exactly what in the makeup of those geometries
> makes the error remotely possible within the operation you are
> performing on them?
>
> ST_MakeValid and ST_Buffer adjust the geometry in (frequently
> insignificant) ways that help operations avoid Topos. But what
> adjustment is likely to avoid the error when using the related valid
> geometries is dependent upon the real cause for the error - and that
> is specific to the geometries at the point identified in the error.
> Whether those manipulations can validly be applied is dependent upon
> your business use tolerance for those adjustments. (buffering a
> polygon by 0.00001 will skew calculated area of a polygon but may not
> result in false positives for an Intersects).
>
> Roxanne
>
>>
>> Thanks!
>>
>>
>>
>>
>>
>>
>> ------------------------------------------------------------------------
>> *From:* Joseph Spenner <joseph85750 at yahoo.com>
>> <mailto:joseph85750 at yahoo.com>
>> *To:* PostGIS Users Discussion <postgis-users at lists.osgeo.org>
>> <mailto:postgis-users at lists.osgeo.org>
>> *Sent:* Thursday, February 26, 2015 8:05 AM
>> *Subject:* Re: [postgis-users] TopologyException: geom is invalid
>>
>> Hello, and thanks for the replies!
>> I'll try those suggestions.
>>
>> Just curiuos though-- which geometry seems to be invalid? Is it the
>> state poly, or the smaller county/zone poly? If there was an invalid
>> geometry, wouldn't it always show up for that state or county? Here's
>> what I observed for the CA issue:
>>
>> 1) I had 3 smaller county poly/geometries in CA. When performing my
>> query, instead of returning the 3 polys, I received the error which I
>> posted in my original thread. I identified it was 1 of those 3. I
>> deleted that 1 offending geometry from my table. After doing so, my
>> query against CA turned up the remaining 2, with no errors. So, that
>> leads me to believe CA is ok. Or is this not a valid assumption?
>> Perhaps the location where that offending intersection would have
>> occurred in the CA poly has an issue, and it doesn't get tickled
>> unless the smaller county zone intersects it?
>>
>> 2) I was able to plot the offending county described above in the
>> GeoJSONLint validation page: http://geojsonlint.com/
>> There didn't appear to be any issues.
>>
>> Thanks!
>>
>> Regards,
>> Joseph Spenner
>>
>>
>>
>>
>>
>>
>>
>>
>> ------------------------------------------------------------------------
>> *From:* Rémi Cura <remi.cura at gmail.com> <mailto:remi.cura at gmail.com>
>> *To:* PostGIS Users Discussion <postgis-users at lists.osgeo.org>
>> <mailto:postgis-users at lists.osgeo.org>
>> *Cc:* Joseph Spenner <joseph85750 at yahoo.com>
>> <mailto:joseph85750 at yahoo.com>
>> *Sent:* Thursday, February 26, 2015 1:28 AM
>> *Subject:* Re: [postgis-users] TopologyException: geom is invalid
>>
>> And also ST_IsSimple (that precisely check for self intersection).
>> Cheers,
>> Rémi-C
>>
>> 2015-02-26 8:32 GMT+01:00 BladeOfLight16 <bladeoflight16 at gmail.com
>> <mailto:bladeoflight16 at gmail.com>>:
>>
>>
>>
>> On Wed, Feb 25, 2015 at 12:14 PM, Joseph Spenner
>> <joseph85750 at yahoo.com <mailto:joseph85750 at yahoo.com>> wrote:
>>
>> DBD::Pg::st execute failed: ERROR: Error performing
>> intersection: TopologyException: Input geom 1 is invalid:
>> Self-intersection at or near point -381688.06935935974
>> -1206669.4272876547 at -381688.06935935974
>> -1206669.4272876547 at ./test.pl <http://test.pl/> line 151.
>>
>>
>> Did you try ST_IsValid to verify the geometry is valid according
>> to the OGC standard? (See
>> http://postgis.net/docs/using_postgis_dbmanagement.html#OGC_Validity.
>> ST_IsValidDetail and ST_IsValidReason are also helpful in this
>> regard.) What happens if you run it through ST_MakeValid? Be
>> aware that ST_MakeValid can sometimes result in
>> GeometryCollections if the input shape is malformed (usually
>> "rings" without enough points are that have different start and
>> end points).
>>
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>
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