Vector remove small lines - Revision history

Neteler: expanded

2014-11-05T10:52:01Z

expanded

← Older revision		Revision as of 10:52, 5 November 2014
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	'''Q:''' How to remove small vector lines? I want to only delete spurious lines.		'''Q:''' How to remove small vector lines? I want only delete spurious lines.

	'''A:''' You may choose from the following approach:		'''A:''' You may choose from the following approach (please read all of them before starting):

	'''Approach 1:'''		'''Approach 1:'''

	~~Considering~~ short vector segments as dangles, use:		To delete isolated lines which are not connected to the main "network", use:
			{{cmd\|v.net.alloc}} in={your input vector} out={output vector} ... (TBD)

			'''Approach 2:'''

			To globally delete short vector segments, considering them as dangles, use:
	{{cmd\|v.clean}} in={your input vector} tool=rmdangle thresh={your threshold} out={output vector}		{{cmd\|v.clean}} in={your input vector} tool=rmdangle thresh={your threshold} out={output vector}

	'''Approach 2:'''		'''Approach 3:'''

	* use {{cmd\|v.build.polylines}} to join broken vector segments into longer segments		* use {{cmd\|v.build.polylines}} to join broken vector segments into longer segments
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	{{cmd\|v.extract}} in=mypolyline out=mypolyline_over5km type=line where="length_km > 5.0"		{{cmd\|v.extract}} in=mypolyline out=mypolyline_over5km type=line where="length_km > 5.0"

	'''Approach 3:'''		'''Approach 4:'''

	~~Remove from vector map~~ all lines with length shorter than 50 map units (thresh: threshold distance (coords,snap,query)):		To remove all lines with a length shorter than 50 map units (thresh: threshold distance (coords,snap,query)) globally:
	{{cmd\|v.edit}} mymap tool=delete query=length thresh=-1,0,-50 type=line		{{cmd\|v.edit}} mymap tool=delete query=length thresh=-1,0,-50 type=line

			You can also define a bounding box in v.edit to limit the operation to a subset of the map.

	== See also ==		== See also ==

Neteler: +v.clean approach

2014-11-04T14:49:18Z

+v.clean approach

← Older revision		Revision as of 14:49, 4 November 2014
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	'''Q:''' How to remove small vector lines? I want to only delete spurious lines.		'''Q:''' How to remove small vector lines? I want to only delete spurious lines.

	'''A1:''' You may the following approach:		'''A:''' You may choose from the following approach:

			'''Approach 1:'''

			Considering short vector segments as dangles, use:
			{{cmd\|v.clean}} in={your input vector} tool=rmdangle thresh={your threshold} out={output vector}

			'''Approach 2:'''

	* use {{cmd\|v.build.polylines}} to join broken vector segments into longer segments		* use {{cmd\|v.build.polylines}} to join broken vector segments into longer segments
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	{{cmd\|v.extract}} in=mypolyline out=mypolyline_over5km type=line where="length_km > 5.0"		{{cmd\|v.extract}} in=mypolyline out=mypolyline_over5km type=line where="length_km > 5.0"

	'''A2:''' ~~Alternative approach:~~		'''Approach 3:'''

	~~Removes~~ from vector map all lines with length shorter than 50 map units (thresh: threshold distance (coords,snap,query)):		Remove from vector map all lines with length shorter than 50 map units (thresh: threshold distance (coords,snap,query)):
	{{cmd\|v.edit}} mymap tool=delete query=length thresh=-1,0,-50 type=line		{{cmd\|v.edit}} mymap tool=delete query=length thresh=-1,0,-50 type=line

Neteler at 14:44, 4 November 2014

2014-11-04T14:44:25Z

← Older revision		Revision as of 14:44, 4 November 2014
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	Removes from vector map all lines with length shorter than 50 map units (thresh: threshold distance (coords,snap,query)):		Removes from vector map all lines with length shorter than 50 map units (thresh: threshold distance (coords,snap,query)):
	{{cmd\|v.edit}} mymap tool=delete query=length thresh=-1,0,-50 type=line		{{cmd\|v.edit}} mymap tool=delete query=length thresh=-1,0,-50 type=line

			== See also ==

			* http://gis.stackexchange.com/questions/48265/how-to-find-dead-ends-in-a-road-network

	[[Category:FAQ]]		[[Category:FAQ]]
	[[Category:Vector]]		[[Category:Vector]]

Neteler at 14:06, 4 November 2014

2014-11-04T14:06:45Z

← Older revision		Revision as of 14:06, 4 November 2014
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	'''A2:''' Alternative approach:		'''A2:''' Alternative approach:

	Removes from vector map all lines with length shorter than 50 map units:		Removes from vector map all lines with length shorter than 50 map units (thresh: threshold distance (coords,snap,query)):
	{{cmd\|v.edit}} -r mymap tool=delete query=length thresh=50 type=line		{{cmd\|v.edit}} mymap tool=delete query=length thresh=-1,0,-50 type=line

	[[Category:FAQ]]		[[Category:FAQ]]
	[[Category:Vector]]		[[Category:Vector]]

Neteler: New

2014-11-04T14:01:11Z

New

New page

'''Q:''' How to remove small vector lines? I want to only delete spurious lines.

'''A1:''' You may the following approach:

* use {{cmd|v.build.polylines}} to join broken vector segments into longer segments
* then use {{cmd|v.to.db}} with option=length (line length) to upload the vector segment lengths to the attribute table
{{cmd|v.db.addcol}} mypolyline column="length_km double precision"
{{cmd|v.to.db}} mypolyline type=line option=length units=k column=length_km
* now use {{cmd|v.extract}} to extract the longer vector segments into a new map according to a threshold you need. Example: Extract line features longer than 5km (cleans out the noise):
{{cmd|v.extract}} in=mypolyline out=mypolyline_over5km type=line where="length_km > 5.0"

'''A2:''' Alternative approach:

Removes from vector map all lines with length shorter than 50 map units:
{{cmd|v.edit}} -r mymap tool=delete query=length thresh=50 type=line

[[Category:FAQ]]
[[Category:Vector]]