Flags:¶

-g

Use geodesic calculation for longitude-latitude locations

-l

Write each output path as one line, not as original input segments.

--overwrite

Allow output files to overwrite existing files

--help

Print usage summary

--verbose

Verbose module output

--quiet

Quiet module output

--ui

Force launching GUI dialog

Parameters:¶

input=name [required]

Name of input vector map
Or data source for direct OGR access

output=name [required]

Name for output vector map

arc_layer=string

Arc layer
Vector features can have category values in different layers. This number determines which layer to use. When used with direct OGR access this is the layer name.
Default: 1

arc_type=string[,string,...]

Arc type
Input feature type
Options: line, boundary
Default: line,boundary

node_layer=string

Node layer
Vector features can have category values in different layers. This number determines which layer to use. When used with direct OGR access this is the layer name.
Default: 2

from_layer=string

From layer number or name
Vector features can have category values in different layers. This number determines which layer to use. When used with direct OGR access this is the layer name.
Default: 1

from_cats=range

From category values
Example: 1,3,7-9,13

from_where=sql_query

From WHERE conditions of SQL statement without ’where’ keyword
Example: income < 1000 and population >= 10000

to_layer=string

Layer number or name
To layer number or name
Default: 1

to_type=string[,string,...]

To feature type
Options: point, line, boundary
Default: point

to_cats=range

To category values
Example: 1,3,7-9,13

to_where=sql_query

To WHERE conditions of SQL statement without ’where’ keyword
Example: income < 1000 and population >= 10000

arc_column=name

Arc forward/both direction(s) cost column (number)

arc_backward_column=name

Arc backward direction cost column (number)

node_column=name

Node cost column (number)

Shortest path and distance between school and nearest hospital¶

Find shortest path and distance from every school to the nearest hospital and show all paths.

Streets are grey lines, schools are green circles, hospitals are red crosses, shortest paths are blue lines:

# connect schools to streets as layer 2
v.net input=streets_wake points=schools_wake output=streets_net1 \


      operation=connect thresh=400 arc_layer=1 node_layer=2
# connect hospitals to streets as layer 3
v.net input=streets_net1 points=hospitals output=streets_net2 \


      operation=connect thresh=400 arc_layer=1 node_layer=3
# inspect the result
v.category in=streets_net2 op=report
# shortest paths from schools (points in layer 2) to nearest hospitals (points in layer 3)
v.net.distance in=streets_net2 out=schools_to_hospitals flayer=2 to_layer=3
# visualization
g.region vector=streets_wake
d.mon wx0
d.vect streets_wake color=220:220:220
d.vect schools_wake color=green size=10
d.vect map=hospitals icon=basic/cross3 size=15 color=black fcolor=red
d.vect schools_to_hospitals

Distance between point source of pollution and sample points along streams¶

Example with streams of the NC sample data set.

# add coordinates of pollution point source of pollution as vector
pollution.txt:
634731.563206905|216390.501834892
v.in.ascii input=pollution.txt output=pollution
# add table to vector
v.db.addtable map=pollution
# add coordinates of sample points as vector
samples.txt:
634813.332814905|216333.590706166
634893.462007813|216273.763350851
634918.660011082|216254.949609689
v.in.ascii input=samples.txt output=samples
# add table to vector
v.db.addtable map=samples
# connect samples and pollution to streams
v.net -c input=streams points=samples output=streams_samples \


         operation=connect node_layer=3 threshold=10 \
v.net -c input=streams_samples points=pollution


         output=streams_samples_pollution operation=connect \


         node_layer=4 threshold=10
# check vector layers
v.category input=streams_samples_pollution option=report
Layer/table: 1/streams_samples_pollution
type       count        min        max
point          0          0          0
line        8562      40102     101351
boundary       0          0          0
centroid       0          0          0
area           0          0          0
face           0          0          0
kernel         0          0          0
all         8562      40102     101351
Layer: 3
type       count        min        max
point          3          1          3
line           0          0          0
boundary       0          0          0
centroid       0          0          0
area           0          0          0
face           0          0          0
kernel         0          0          0
all            3          1          3
Layer: 4
type       count        min        max
point          1          1          1
line           0          0          0
boundary       0          0          0
centroid       0          0          0
area           0          0          0
face           0          0          0
kernel         0          0          0
all            1          1          1
# calculate distance between sample points and pollution point source
v.net.distance input=streams_samples_pollution \


      output=distance_samples_to_pollution from_layer=3 to_layer=4
# check results
v.report map=distance_samples_to_pollution@vnettest option=length
cat|tcat|dist|length
1|1|100.0|100.0
2|1|200.0|200.0
3|1|231.446|231.446