How to check if every segments of a road have the same directions?
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1 Solution
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XanderBakker
The are many ways to validate if there are segments with the wrong direction. For instance manually, by applying a symbology that includes line decoration:
Which will show you where you have problems in your data:
You can also create end and start points in separate featureclasses form the lines using Feature Vertices to Points:
And symbolize those:
You can also apply hatching (About displaying hatches—Help | ArcGIS Desktop ) to validate the M values of the road (are they continuous):
Or you can analyze the start and end featureclasses with a Generate Near Table and validate where you have start points without end point (although you would need to exclude the start and end points of a route.
Or create routes to see if the routes makes sense when you apply the M values of the road segments.
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by
XanderBakker
See below some sample code that could be a start:
def main():
import arcpy
# input fc and name of field containing route name
fc = r'C:\GeoNet\RoadDirection\test.gdb\roads_m'
fld_name = 'RouteName'
tolerance = 1
# sr
sr = arcpy.Describe(fc).spatialReference
# create dictionary of data
dct_routes = {}
flds = ('OID@', 'SHAPE@', fld_name)
with arcpy.da.SearchCursor(fc, flds) as curs:
for row in curs:
dct_data = {}
oid = row[0]
polyline = row[1]
route_name = row[2]
if route_name in dct_routes:
dct_data = dct_routes[route_name]
dct_data[oid] = polyline
else:
dct_data[oid] = polyline
dct_routes[route_name] = dct_data
# determnine first segment of route based on minimum M value
dct_possible_errors = {}
for route_name, dct_data in sorted(dct_routes.items()):
print "dct_possible_errors", dct_possible_errors
oid = GetFirstSegmentOfRouteOnMvalue(dct_data)
print
print " - GetFirstSegmentOfRouteOnMvalue:", route_name, oid
lst_processed = [oid]
dct_start_pnts = CreateDictionaryStartOrEndPoints(dct_data, "start")
dct_end_pnts = CreateDictionaryStartOrEndPoints(dct_data, "end")
print route_name
print " - len:", len(dct_data.keys())
print " - oid:", oid
# start connecting segments
lst_todo = [o for o in dct_data.keys() if not o in lst_processed]
while len(lst_todo) != 0:
start_pnt = dct_start_pnts[oid]
end_pnt = dct_end_pnts[oid]
print " - lst_processed:", lst_processed
print " - lst_todo:", lst_todo
oid_near_end, dist_near_end, type_near_end = FindPointsNearEnd(oid, "end", dct_start_pnts, dct_end_pnts, lst_processed)
print " - FindPointsNearStartorEnd-end :", oid_near_end, dist_near_end, type_near_end
oid_near_start, dist_near_start, type_near_start = FindPointsNearStart(oid, "start", dct_start_pnts, dct_end_pnts, lst_processed)
print " - FindPointsNearStartorEnd-start:", oid_near_start, dist_near_start, type_near_start
from_part = "end"
to_part = "not set"
if dist_near_start < tolerance:
print " - connect to start is option..."
print " - oid to connect to:", oid_near_start
to_part = "start"
print "ERROR possible flip line case"
if dist_near_end < tolerance:
print " - connect to end is option..."
print " - oid to connect to:", oid_near_end
to_part = "end"
print " - from - to: ", from_part, " - ", to_part
if to_part == "end":
print "from_part is start, possible ERROR flip case!"
lst_todo.remove(oid_near_end)
lst_processed.append(oid_near_end)
oid = oid_near_end
print " - ERROR is end, Flip!:", oid_near_end
if route_name in dct_possible_errors:
errors = dct_possible_errors[route_name]
errors.append(oid)
dct_possible_errors[route_name] = errors
else:
dct_possible_errors[route_name] = [oid]
print " - added:", route_name, oid
elif to_part == "start":
print "to_part is end, OK"
lst_todo.remove(oid_near_start)
lst_processed.append(oid_near_start)
oid = oid_near_start
print " - OK is start :", oid_near_start
else:
print "no candidates available in tolerance"
print " - still to do:", lst_todo
lst_todo = []
print
for route_name, errors in dct_possible_errors.items():
if len(errors) > 0:
print route_name, errors
def FindPointsNearStart(oid, start_or_end, dct_start_pnts, dct_end_pnts, lst_exclude):
if start_or_end == "start":
pnt = dct_start_pnts[oid]
else:
pnt = dct_end_pnts[oid]
dist_min = 9999
oid_min = -1
type_min = "not set"
# determine distance bewteen point and start of others
for oid_i, pnt_i in dct_start_pnts.items():
if not oid_i in lst_exclude:
dist_i = GetDistance(pnt.X, pnt.Y, pnt_i.X, pnt_i.Y)
if dist_i < dist_min:
dist_min = dist_i
oid_min = oid_i
type_min = "start"
return oid_min, dist_min, type_min
def FindPointsNearEnd(oid, start_or_end, dct_start_pnts, dct_end_pnts, lst_exclude):
if start_or_end == "start":
pnt = dct_start_pnts[oid]
else:
pnt = dct_end_pnts[oid]
dist_min = 9999
oid_min = -1
type_min = "not set"
# determine distance bewteen point and start of others
for oid_i, pnt_i in dct_end_pnts.items():
if not oid_i in lst_exclude:
dist_i = GetDistance(pnt.X, pnt.Y, pnt_i.X, pnt_i.Y)
if dist_i < dist_min:
dist_min = dist_i
oid_min = oid_i
type_min = "end"
return oid_min, dist_min, type_min
def FindPointsNearStartorEnd(oid, start_or_end, dct_start_pnts, dct_end_pnts, lst_exclude):
if start_or_end == "start":
pnt = dct_start_pnts[oid]
else:
pnt = dct_end_pnts[oid]
dist_min = 9999
oid_min = -1
type_min = "not set"
# determine distance bewteen point and start of others
for oid_i, pnt_i in dct_start_pnts.items():
if not oid_i in lst_exclude:
dist_i = GetDistance(pnt.X, pnt.Y, pnt_i.X, pnt_i.Y)
if dist_i < dist_min:
dist_min = dist_i
oid_min = oid_i
type_min = "start"
# determine distance bewteen point and start of others
for oid_i, pnt_i in dct_end_pnts.items():
if not oid_i in lst_exclude:
dist_i = GetDistance(pnt.X, pnt.Y, pnt_i.X, pnt_i.Y)
if dist_i < dist_min:
dist_min = dist_i
oid_min = oid_i
type_min = "end"
return oid_min, dist_min, type_min
def GetDistance(x1, y1, x2, y2):
import math
return math.hypot(x2-x1, y2-y1)
def CreateDictionaryStartOrEndPoints(dct_data, start_or_end):
dct_pnts = {}
for oid, polyline in dct_data.items():
if start_or_end == "start":
dct_pnts[oid] = polyline.firstPoint
else:
dct_pnts[oid] = polyline.lastPoint
return dct_pnts
def GetFirstSegmentOfRouteOnMvalue(dct_data):
m_min = 99999
oid_min = -1
for oid, polyline in dct_data.items():
for part in polyline:
for pnt in part:
m = pnt.M
if m < m_min:
m_min = m
oid_min = oid
return oid_min
if __name__ == '__main__':
main()It threw as result that feature with OID 5, route "B" was in the wrong direction (although a lot of testing is still required):
Before you start to use this script, please keep the following in mind:
- This code selects the first segment (feature) based on the minimum M value
- The first feature defined the direction, if you have 10 segments in a route and the first points in a certain direction and the rest in the other, all 9 segments would be identified as "wrong"
- If you would like to define the correct direction based on the majority of the segments, you should determine if this is on number of features or combined length.
- There can be infinite exceptions that could yield undesired results
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by
I have done some test with your code on my example data. I have attached the data. You will find that:
- in my example data every segment of a given road must start with M value =0,
- the right direction is the direction of the first segment [Segment_ID] of a given road, that is the minimum value (number) in field [Segment_ID] for a given road number [RouteName]
Below screenshot of my example roads:
The right direction for whole road indicates:
- Road A – segment 1
- Road B – segment 4
- Road C – segment 7
So script should report errors:
- Road A, Segment 2 (A, 2)
- Road B, Segment 6 (B, 6)
- Road C, Segment 8, 9, 10 (C,8; C,9; C,10)
For now, code indicates errors only at segment (A,2).
Please for further help.
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