Linear reference should do the job, but can be bulky. This is why I am using this script:
# Import arcpy module
import arcpy, os, traceback, sys,time
from arcpy import env
env.overwriteOutput = True
infc = arcpy.GetParameterAsText(0)
routeid = arcpy.GetParameterAsText(1)
outfc=arcpy.GetParameterAsText(2)
fields = [f for f in arcpy.ListFields(infc)]
fieldNames = [f.name for f in arcpy.ListFields(infc)]
# define number of lines
result=arcpy.GetCount_management(infc)
nF=int(result.getOutput(0))
d=arcpy.Describe(outfc)
SR_p=d.spatialReference
d=arcpy.Describe(infc)
SR=d.spatialReference
if SR_p.name<>SR.name:
arcpy.AddError("\nDifferent projections. Quit\n")
raise SystemExit('Quit...')
## initial point layer clean-up
fieldsP = [f for f in arcpy.ListFields(outfc)]
fieldNamesP = [f.name for f in arcpy.ListFields(outfc)]
dToLine,dAlong="D_TO_LINE","D_ALONG"
for ent in [routeid,dToLine,dAlong]:
if ent in fieldNamesP:
arcpy.DeleteField_management(outfc, ent)
outFolder, theFile="in_memory","intLines"
env.workspace = outFolder
try:
def showPyMessage():
arcpy.AddMessage(str(time.ctime()) + " - " + message)
def CalcChainage():
pC,lineID,dToLine,Chainage=theRow
shp=dictFeatures[lineID]
theRow[2]=pC.distanceTo(shp)
theRow[3]=shp.measureOnLine(pC)
return
with arcpy.da.SearchCursor(infc, ("SHAPE@",routeid)) as rows:
dictFeatures = {}
for feat,theID in rows:
dictFeatures[theID]=(feat)
del rows
arcpy.SpatialJoin_analysis(outfc, infc, "theJoin", "JOIN_ONE_TO_ONE", "KEEP_ALL", "", "CLOSEST","",dToLine)
arcpy.AddField_management("theJoin", dAlong, "DOUBLE")
## calculate chainage
result=arcpy.GetCount_management("theJoin")
nF=int(result.getOutput(0))
arcpy.AddMessage("\nComputing chainage...")
arcpy.SetProgressor("step", "", 0, nF,1)
with arcpy.da.UpdateCursor("theJoin", ("SHAPE@",routeid,dToLine,dAlong)) as rows:
for theRow in rows:
CalcChainage()
rows.updateRow(theRow)
arcpy.SetProgressorPosition()
del rows
##defining the type of route id field
n=fieldNames.index(routeid)
fType=fields[n].type
fLength=fields[n].length
try:
if fType=="String":
arcpy.AddField_management(outfc, routeid, "TEXT","","",fLength)
if fType=="Integer":
arcpy.AddField_management(outfc, routeid, "LONG")
if fType=="SmallInteger":
arcpy.AddField_management(outfc, routeid, "SHORT")
except: pass
try:
arcpy.AddField_management(outfc, dToLine, "DOUBLE")
arcpy.AddField_management(outfc, dAlong, "DOUBLE")
except: pass
arcpy.AddMessage("Transferring calcs to points...\n")
vFT=arcpy.da.TableToNumPyArray("theJoin",(routeid,dToLine,dAlong))
arcpy.SetProgressor("step", "", 0, nF,1)
with arcpy.da.UpdateCursor(outfc,(routeid,dToLine,dAlong )) as rows:
n=0
for theRow in rows:
theRow=vFT[n]
rows.updateRow(theRow)
arcpy.SetProgressorPosition()
n+=1
del vFT, rows
except NameError, theMessage:
arcpy.AddMessage (theMessage)
except:
message = "\n*** PYTHON ERRORS *** "; showPyMessage()
message = "Python Traceback Info: " + traceback.format_tb(sys.exc_info()[2])[0]; showPyMessage()
message = "Python Error Info: " + str(sys.exc_type)+ ": " + str(sys.exc_value) + "\n"; showPyMessage()
Script expects these parameters:
To get this:
Perhaps you'd like to merge (dissolve) your polylines into single line. Make sure it won't create multipart shape, i.e. ends of segments must be snapped.
Script tested on shapefiles.
Best Answer
This code will work on the lastest dev build of QGIS.
I know you said you are not very familiar with Python code but you should be able to run this pretty easy. Copy the above code into a file (mine is called
locate.py
) and place it in your~/.qgis/python
if you are on Windows 7 that will be inC:\Users\{your user name}\.qgis\python\
or on Windows XPC:\Documents and Settings\{your user name}\.qgis\python\
Once the file is in the python folder open QGIS and select some line objects.
Then open the Python console and run the following code:
The result should look something like this
If you want to run it again just select some more lines and run
locate.createRandomPoints(10)
in the Python console again.Note: locate.createRandomPoints(10) the 10 here is the number of points to generate per line