[QGIS-Developer] Geodesic Line Simplification

[Nyall Dawson]

On Wed, 2 Oct 2019 at 01:30, C Hamilton <adenaculture at gmail.com> wrote:
>
> I am guessing this is working on Cartesian coordinates and not geodesic which is fine if you have a local projection. I think I will go ahead and implement some similar geodesic algorithms. Thank you for the GRASS link. It will help.

Hi Calvin,

I think there's a strong use case for adding this to the c++ API.
Would you be willing to put together a proof of concept in Python code
and I'll port it to c++ for you?

Nyall


>
> Thanks,
>
> Calvin
>
> On Tue, Oct 1, 2019 at 7:45 AM Áron Gergely <aron.gergely at rasterra.nl> wrote:
>>
>> Hi Calvin and list,
>>
>> Have you looked at the GRASS GIS v.generalize tool? https://grass.osgeo.org/grass64/manuals/v.generalize.html
>>
>> The Douglas-Peucker algorithm is implemented there and I have used that with (topologic)success recently on many touching polygons. Should work for polylines too!
>>
>> Best regards,
>> Aron
>>
>> On 01/10/2019 08:19, Tim Sutton wrote:
>>
>> Hi
>>
>> On 26 Sep 2019, at 17:13, C Hamilton <adenaculture at gmail.com> wrote:
>>
>> Are there any geodesic QGIS algorithms that simplify lines? "Simplify" just uses the projection units of measure. If there isn't I thought I would add this to the Shape Tools plugin. I could easily implement the Douglas-Peucker algorithm using geodesic math.
>>
>> For GPS tracks I also see a need to throw out all points that are less than a certain distance or less than a certain time interval. I don't see any simplification algorithms that make use of time. Am I just missing them?
>>
>>
>> No I don’t think we have any time based simplifiers - would be a great addition!
>>
>> Regards
>>
>> Tim
>>
>>
>>
>>
>> Thanks,
>>
>> Calvin
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>> —
>>
>>
>>
>>
>>
>>
>>
>>
>> Tim Sutton
>>
>> Co-founder: Kartoza
>> Ex Project chair: QGIS.org
>>
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>>
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>>
>> I'd love to connect. Here's my calendar link to make finding time easy.
>>
>>
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