[Qgis-user] [Qgis-developer] About a 'directed' LINESTRING (e.g. for oneway streets)?

[Andreas Neumann]

Hi,

In waste-water management line direction also matters. Operators always
digitize the LINESTRING geometry downstream from higher to lower levels.

So far I did not have any issue with this - esp. not with storage,
rendering, import/export. There may be some edge cases with some
analysis tool - but so far I haven't come across one such issue.

Personally I would prefer if a tool for switching line direction would
be in QGIS core rather than in a plugin. I hope that we can do that for
QGIS 2.1 - I don't consider changing the line direction as exotic or
special that it could not reside in the core.

Please note that the current version of the LineSwitch plugin is not
compatible with QGIS 2.0. It probably wouldn't be too hard to fix this,
though.

Andreas

Am 01.09.2013 16:54, schrieb Anita Graser:
> Hi Stefan,
> 
> Nathan developed the line direction switcher
> http://gis.stackexchange.com/questions/9261/how-can-i-switch-line-direction-in-qgis
> 
> 
> I do a lot of work with street networks where line direction is very
> important. So far, I haven't run into any problems due to the direction
> being messed up by any tools.
> 
> Best wishes,
> Anita
> 
> 
> 
> Am 01.09.2013, 15:43 Uhr, schrieb Stefan Keller <sfkeller at gmail.com>:
> 
>> Hi Alexandre
>>
>> Thanks for the quick answer and the hint to the plugin LineSwitch (from
>> Underdark?).
>> Besides that the plugin page is'nt online currently for me - I'd like to
>> emphasize that my main question is about the reliability through all
>> processing steps to maintain the direction.
>> I actually want to hear if anybody had issues when importing/exporting
>> directed lines with OGR or analysing them with fTools or Sextante.
>>
>> Yours, Stefan
>>
>>
>> 2013/9/1 Alexandre Neto <senhor.neto at gmail.com>
>>
>>> Linestrings have a direction already, you can use marker lines with
>>> arrows
>>> to represent the original direction. For analysis you can revert the
>>> polyline direction using it's attributes, or using the switch the
>>> direction
>>> of polyline plugin [1] to actually invert vertex order.
>>>
>>> Alexandre Neto
>>>
>>>
>>> [1] http://plugins.qgis.org/plugins/lineswitch/
>>>
>>>
>>> On Sun, Sep 1, 2013 at 1:53 PM, Stefan Keller <sfkeller at gmail.com>
>>> wrote:
>>>
>>>> I'm designing a spatial database and like to introduce a LINESTRING
>>>> where
>>>> the direction is important, e.g. to describe a oneway street or a water
>>>> pipe. I indicate this by another attribute, e.g. "direction:
>>>> BOOLEAN", or
>>>> "direction: ENUM(both, as_is, reverse)
>>>>
>>>> A "directed line" means that the order of the coordinates of a
>>>> linestring
>>>> value is important - like in a directed graph - and needs to remain the
>>>> same whatever happens to it e.g. when importing, storing, retrieving,
>>>> analysing or rendering...
>>>>
>>>> Does anybody have had any issues to manage "directed lines" in QGIS
>>>> (OGR,
>>>> extensions, etc.)?
>>>>
>>>> Yours, Stefan
>>>>
>>>>
>>>> _______________________________________________
>>>> Qgis-developer mailing list
>>>> Qgis-developer at lists.osgeo.org
>>>> http://lists.osgeo.org/mailman/listinfo/qgis-developer
>>>>
>>>
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