[Qgis-user] topology checker - Check if point features are covered by line features

[Nicolas Cadieux]

Bug report has been made

#35831


On 2020-04-17 12:58 p.m., Nicolas Cadieux wrote:
> Hi,
>
> Small correction,
>
> If you extract the end nodes (vertices) of the line, you can use the 
> following rule.  End node layer must be covered by endpoints of line 
> layer or node layer must be covered by line.  I therefore assume the 
> QGIS topology checker can work for endnode only and not for "middle 
> node" of the line.  This is should be reported as a bug I think.
>
> Nicolas
>
> On 2020-04-17 12:42 p.m., Nicolas Cadieux wrote:
>> Hi Marshal,
>>
>> I looked at your data. The first problem is that none or your line 
>> nodes intersect with a point.  It looks close... but it's not close 
>> enough.  By using "snap geometry location", I was able to create a 
>> new line that snaps to your point.  (called Topologie snapped_line in 
>> the file I will send you in private). A "Select by location" or a 
>> "Join Attributes by location" confirms that the points now intersect 
>> the Topologie snapped line layer. The Join Attributes by location 
>> will permit you to find the problems as you can discard records that 
>> do not intersect.  This will give you what you want.
>>
>> As for the topology Checker, it seems that a line cannot cover a 
>> point or a point cannot cover a line even if point and line nodes 
>> intersect (Can someone confirm this?).  I can only assume that QGIS 
>> works with the correct assumption that a point and a line does not 
>> have a surface to cover and therefore, cannot cover anything.  I 
>> assume, based on your observations that ESRI does not follow that 
>> assumption.
>>
>> You can however create a 1 m buffer around your line (Topologie 
>> Buffered_line in the file).  Then, you can create the rule (polygon 
>> must contain point). That rule will work in the topology Checker.
>>
>> Cheers!
>>
>> Nicolas
>>
>>
>> On 2020-04-13 10:25 a.m., Nicolas Cadieux wrote:
>>> Hi,
>>>
>>> I don’t have QGIS in front of me.  I looked around on the the net 
>>> and was surprised to see the «covered By » option for points and 
>>> lines.  Unless a line is snapped, or intersects a point exactly on a 
>>> Line node, it’s just about impossible to calculate if a line « 
>>> covers » a point.  This is something easy to do with a polygon but 
>>> not a line because of float point precision error.  You could buffer 
>>> the lines and see if that helps. You could create a 1m buffer on the 
>>> line (or the point).  Make sure both layers are in the same crs so 
>>> that additional calculations don’t need to be done.
>>>
>>> You could at the « select by location » side.  I would look at « 
>>> snap with » or «intersects with »options.
>>>
>>> Nicolas Cadieux
>>> Ça va bien aller!
>>>
>>>> Le 13 avr. 2020 à 06:11, Marshal Mappers <marshalmappers at gmail.com> 
>>>> a écrit :
>>>>
>>>> 
>>>> Hello everyone,
>>>> I want to use the topology checker to check if point features are 
>>>> covered by line features. For example are the bus stops covered by 
>>>> the bus lines.
>>>> Therefore I use the topology checker with the following rule: 
>>>> "points" must be covered by "lines". But I get the error for all 
>>>> points that "point is not covered by segment".
>>>> I even get the error for points that I edited on the line with 
>>>> snapping.
>>>> Here my questions:
>>>> 1. Is it possible to check if point features are covered by line 
>>>> features? With topology checker? In general?
>>>> 2. What does the rule: "points" must be covered by "lines"check? 
>>>> Under what cicumstances is a point feature covered by a line feature?
>>>>
>>>> I tried this in QGIS Versions 2.18.26; 3.4.15; 3.10.2
>>>> My OS ist Windows 10
>>>> I tried with shapefiles and geopackage layers
>>>> The CBS of point and line layers are the same. Here I tried the 
>>>> coordinate systems with epgs: 31468 (DHDN / 3---degree Gauss-Kruger 
>>>> zone 4) and 25832 (ETRS89 / UTM zone 32N).
>>>> If anyone could explain or point me to the right direction, that 
>>>> would be awesome.
>>>>
>>>> Thank you!
>>>>
>>>> Best regards
>>>>
>>>> Marshal
>>>> _______________________________________________
>>>> Qgis-user mailing list
>>>> Qgis-user at lists.osgeo.org
>>>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
>>>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
>>> _______________________________________________
>>> Qgis-user mailing list
>>> Qgis-user at lists.osgeo.org
>>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
>>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
>> _______________________________________________
>> Qgis-user mailing list
>> Qgis-user at lists.osgeo.org
>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
> _______________________________________________
> Qgis-user mailing list
> Qgis-user at lists.osgeo.org
> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/qgis-user/attachments/20200417/9e076672/attachment.html>