Re: [GRASS-user] Break lines in vector A at locations of points in vector B

[thepattonian]

Vincent,

I’ll try your suggestion, thanks. Vector B is not a subset of vector A, but 
rather it contains all vertices of vector A.

--
Eric

> On Mar 6, 2018, at 1:26 PM, Vincent Bain  wrote:
> 
> Hello Eric,
> did you try v.split on vector A, with the vertices argument set to 2?
> (or maybe does vector B contain only a subset of A vertices)
> 
> Vincent.
> 
> Le mardi 06 mars 2018 à 16:50 +, Patton, Eric (NRCan/RNCan) a
> écrit :
>> Hi,
>> 
>> I have two vector maps, vector A is a line vector representing
>> coastline, and vector B is vector points which are the vertices of
>> vector A. Is there a way to split vector A into line segments using
>> vector B as breakpoints? 
>> 
>> v.edit tool=break kind of does this, but seems to want coordinates
>> given one at a time. I have hundreds of thousands of points, and this
>> doesn't seem an efficient way of doing it. 
>> 
>> Thanks,
>> 
>> ~ Eric. 
>> 
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[GRASS-user] Joining attributes of points to spatially-coincident line vertices

[thepattonian]

I have a high-resolution vector coastline, and I extracted the vertices of this 
coastline to points using 'v.to.points use=vertex'. I am trying to find the 
nearest raster slope value from another map to these points, and then upload 
this slope to the attribute table of the vector points coastline. To do this, I 
converted the raster slope map to points with r.to.vect, and successfully 
uploaded the nearest slope value from the now vector slope map to the vector 
points coastline with v.distance, using a dmax=200.

Ok, now to my problem: I want to get the vector coastline points back onto the 
original vector *lines* coastline, with all the point attributes as well. Since 
the vector coastline points were derived from the vertices of the coastline map 
in the first place, they are spatially  coincident, but I can't find a 
processing method that does this. Ideally, I suppose the coastline points map 
could act as breakpoints to the coastline polyline map, and the attributes 
would be transferred based on a buffer of something like one metre or less. 

Any ideas on how I might do this?

Thanks,

--
Eric
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