[GIS] Split Lines with Points Layer Tool

qgis

I asked a question a while ago to figure out how to split a line layer with a points layer using QGIS, but cannot, however, get the accepted answer to work due to limitations of my knowledge and the fact that i'm working on Windows 7. I noticed this feature request that dates from about a year ago, requesting a tool that accomplishes exactly what I need. I've been looking for it, don't see it, and am wondering if it is currently an available tool and i'm just not looking in the right spot or not.

Best Answer

The Networks plugin has a function called "Connect":

This tool allows you to connect node layer objects to a linear objects layer. Each point will be connected to the nearest polyline, if the shortest distance to the polyline is lower than the search radius, the polyline will be split in two parts from each side of the connection point, in order to preserve the network topology. NB : Multilinestrings are ignored

Related Solutions

QGIS – Split Lines at Intersection Points

There is few resolutions of this issue, maybe there are few better ones but this two should do also:

'By hand' (in steps)

Cut every line with another line which intersects it

Create table road_1 as 
  Select 
    row_number() over() as ID,
    input.name,
    (st_dump(st_split(input.geom, blade.geom))).geom as geom
  from roads input
  join roads blade on st_intersects(input.geom, blade.geom);

Now you've got few too much lines cause every time you're splitting one line into 2 parts, so you have to delete all lines that are covering another smaller ones (Thats why ST_NODE exists)

delete from road_1 a
where exists 
  (
  select 1 from road_1 b where a.id != b.id and st_coveredby(b.geom,a.geom)
  );

Automagically

Splitting every line in point of intersection with another line is one of things you have to do to create road topology so maybe it'll be easiest to get familiar with function pgr_createTopology of PG Routing project.

This workshop could be helpfull

QGIS – Alternatives to Zonal Statistics which Include Partial Pixels

I think you hit on your best option, which is to convert the raster to a vector and then intersect the result with your polygon layer.

As a way of explanation regarding the frustration you're experiencing with Zonal Statistics (and actually this will also apply to your idea of cropping or "clipping" the raster), there is no alternative way for this to operate; a single raster cell has to be either in or out.

You also mention that some of your "zones" (ie. polygons) overlap. This will also negate results of a standard Zonal Statistics tool since most of those explicitly mention that they do not account for this and recommend running the tool over each feature separately if this is the case.

Best Answer

Related Solutions

QGIS – Split Lines at Intersection Points

QGIS – Alternatives to Zonal Statistics which Include Partial Pixels

Related Question