[gdal-dev] R: Problem using ogrlineref

[Dmitry Baryshnikov]

Hi Nicola,

The first and last segments usually have beg and end fields value not a 
multiple of 1000.
I.e. begin = 576 m, end 1000 m or begin 76200 m, end 76234 m
This is ok, and ogrlineref correctly woks with this case.

I think, that you can try to play with your data without equal parts 
sizes. But ogrlineref need - beg (double), end(double) and scale 
(double) fields.
Scale - is spatial length of you part divided on linear lenght.
I.e. scale = part.get_Length() / (end - beg)

Best regards,
     Dmitry

07.06.2016 18:25, Nicola Baraldo (ICONSULTING) пишет:
>
> Hi Dmitry,
>
> thank you for you response. There is a way to do the step 2 using GDAL?
>
> Moreover, if the path lengths are not multiple of the split size (e.g. 
> 1000m), how the last segment is handled?
>
> Best regards,
>
> Nicola
>
> *Da:*gdal-dev [mailto:gdal-dev-bounces at lists.osgeo.org] *Per conto di 
> *Dmitry Baryshnikov
> *Inviato:* martedì 7 giugno 2016 16:16
> *A:* gdal-dev at lists.osgeo.org
> *Oggetto:* Re: [gdal-dev] Problem using ogrlineref
>
> Hi Nicola,
>
> The idea of ogrlineref was follow:
> 1. You have layer with some lines and some reper points with known 
> linear coordinates
> 2. The reper points divide lines on equal parts (e.i. 1000 m) - this 
> is important that parts should be equal
> 3. The result file will have special structure (required fields: beg, 
> end, scale, and some optional)
> 4. During referencing  ogrlineref make attribute query and get needed 
> part based on beg and end fields (which is rather fast), and than calc 
> point position inside this part.
>
> In your case, the simple way is to extract begin and end point of your 
> lines and make them reper points. After that all steps are usual.
>
> There is no sense to move other fields into the parts file from your 
> original datasource. But you can use -lf option to store some value 
> and use it in future for join with your original data.
>
> Best regards,
>      Dmitry
>
> 07.06.2016 15:19, Nicola Baraldo (ICONSULTING) пишет:
>
>     Hi guys,
>
>     I am trying to split some routes into segments of the same length
>     (dynamic segmentation) using ogrlineref command.
>
>     My data is stored in a shapefile containing a set of paths, for
>     each path I know the length in meters.
>
>     I have tried ogrlineref with –create, –get_coord and - get_subline.
>
>     For the first option I don’t have a reper datasource to provide
>     because I don’t have mile-stones, are they really necessaries?
>
>     The second and third options give me the following error for each
>     path contained in the input shapefile; with –get_coord I have
>     tried both options “–m 0” and “–m 1000”, with –get_subline I have
>     tried “-mb 0 -me 1” options.
>
>
>
>     Can someone help me using this command? Is there a better way to
>     perform dynamic segmentation using GDAL?
>
>     Moreover my shapefile contains also a lot of other fields, there
>     is a way to keep these information also in the output file?
>
>     Thanks,
>
>     Nicola
>
>
>
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