[postgis-tickets] [PostGIS] #5267: [Enhacement] Extrapolate Linestring rate and distance support

[PostGIS]

#5267: [Enhacement] Extrapolate Linestring rate and distance support
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  Reporter:  latot        |      Owner:  pramsey
      Type:  enhancement  |     Status:  new
  Priority:  medium       |  Milestone:  PostGIS 3.3.2
 Component:  postgis      |    Version:  3.3.x
Resolution:               |   Keywords:
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Description changed by latot:

Old description:

> Hi all, I think would be great to can extrapolate linestrings, for this
> case I'm thinking when we want to extend a linestring, there is a
> stackoverflow with a good answer for this:
>
> https://gis.stackexchange.com/a/269524/213252
>
> It proposes extend a segment where the final length is
> actual_length*rate_length + constant_rate. I think is a good concept.
>
> I'll extend the concept, instead of just "extrapolate" a linestring in
> the end and start, we can extrapolate a segment, like ST_SetPoint, where
> we can extend a segment specifying  the segment id (0 for first -1 for
> the last one). This is a way to do it, but I don't know if is the best
> interpretation to get concept functions in a general way, or maybe is
> just too general, but it is flexible.
>
> So, here a summary I think would be fine to have before start coding.
>
> Extrapolate the first and last segment of a linestring, or just
> extrapolate the "i" segment, their start/end points?
>
> What would be the extrapolation of a multilinestring?
>

> And a last thing, usually the easiest one is the geometry extrapolation,
> just the line equation, while the geography extrapolation is not trivial
> and does not works the method posted in stackoverflow, would be great
> have both of them.
>
> Thx!

New description:

 Hi all, I think would be great to can extrapolate linestrings, for this
 case I'm thinking when we want to extend a linestring, there is a
 stackoverflow with a good answer for this:

 https://gis.stackexchange.com/a/269524/213252

 It proposes extend a segment where the final length is
 actual_length*rate_length + constant_rate. I think is a good concept.

 I'll extend the concept, instead of just "extrapolate" a linestring in the
 end and start, we can extrapolate a segment, like ST_SetPoint, where we
 can extend a segment specifying  the segment id (0 for first -1 for the
 last one). This is a way to do it, but I don't know if is the best concept
 for the function maybe is too general, but it is flexible.

 So, here a summary I think would be fine to have before start coding.

 Extrapolate the first and last segment of a linestring, or just
 extrapolate the "i" segment, their start/end points?

 What would be the extrapolation of a multilinestring?


 And a last thing, usually the easiest one is the geometry extrapolation,
 just the line equation, while the geography extrapolation is not trivial
 and does not works the method posted in stackoverflow, would be great have
 both of them.

 Thx!

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Ticket URL: <https://trac.osgeo.org/postgis/ticket/5267#comment:1>
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