[GIS] How to show line symbol (arrow) independently of line length in ArcGIS

arcgis-10.2arcgis-desktopdirectionlinesymbology

I am manually creating a polyline layer in ESRI geodatabase. Lines are of 2 vertices (start-end), variable length but all very short. I am using directional symbol with arrow at the end (or middle). And I have a small annoying problem: I cannot see the shortest lines. The arrow just disappears when its size is less than the line at that scale. What I get is this:

And I have troubles to see short lines like the upper two especially when I add more layers to the map, because I am creating the lines based on other geodatabase layers.

Increasing the width is not good because it shows a perpendicular expansion of a real line. I just want ArcGIS to show me the arrow symbol always, no matter the visible length of the line. I was searching in Symbol properties as it was advised also here
Showing directional line symbol in ArcGIS for Desktop?
but could not find the solution. When I google, I find only opposite situations (people want to show different symbols depending on the length). Converting line ends to points to show symbols is not possible because I am editing the layer and adding new lines. So I really need to see them well, and their direction. What I want is this:

I am using ArcGIS 10.2 for Desktop. Maybe this is a fault of ArcGIS? Because QGIS is showing arrows as I need:

Best Answer

You may add a triangle marker point style at the end of line "end". This should show at all zoom levels and show on any new features that are added. For details see this q/a:

Arrow Representation/Symbology

Related Solutions

[GIS] Extending line by specified distance in ArcGIS for Desktop

Well I think I've gotten it down for lines of any vertex count. I haven't attempted multipart lines since I've never messed with it in arcpy. The coding was made a bit more difficult since there isn't write access to the lastPoint property for Geometry objects. Instead of using the slope (which was my initial thought), I used the code from this SO question. It doesn't rely on trigonometry, so it should be slightly more efficient. The following code works by moving the endpoint of a line to a new coordinate that lies along the prolongation of a line from the last two vertices. I tested it on a shapefile.

from math import hypot
import collections
from operator import add
import arcpy

layer = arcpy.GetParameterAsText(0)
distance = float(arcpy.GetParameterAsText(1))

#Computes new coordinates x3,y3 at a specified distance
#along the prolongation of the line from x1,y1 to x2,y2
def newcoord(coords, dist):
    (x1,y1),(x2,y2) = coords
    dx = x2 - x1
    dy = y2 - y1
    linelen = hypot(dx, dy)

    x3 = x2 + dx/linelen * dist
    y3 = y2 + dy/linelen * dist    
    return x3, y3

#accumulate([1,2,3,4,5]) --> 1 3 6 10 15
#Equivalent to itertools.accumulate() which isn't present in Python 2.7
def accumulate(iterable):    
    it = iter(iterable)
    total = next(it)
    yield total
    for element in it:
        total = add(total, element)
        yield total

#OID is needed to determine how to break up flat list of data by feature.
coordinates = [[row[0], row[1]] for row in
               arcpy.da.SearchCursor(layer, ["OID@", "SHAPE@XY"], explode_to_points=True)]

oid,vert = zip(*coordinates)

#Construct list of numbers that mark the start of a new feature class.
#This is created by counting OIDS and then accumulating the values.
vertcounts = list(accumulate(collections.Counter(oid).values()))

#Grab the last two vertices of each feature
lastpoint = [point for x,point in enumerate(vert) if x+1 in vertcounts or x+2 in vertcounts]

#Convert flat list of tuples to list of lists of tuples.
#Obtain list of tuples of new end coordinates.
newvert = [newcoord(y, distance) for y in zip(*[iter(lastpoint)]*2)]    

j = 0
with arcpy.da.UpdateCursor(layer, "SHAPE@XY", explode_to_points=True) as rows:
    for i,row in enumerate(rows):
        if i+1 in vertcounts:            
            row[0] = newvert[j]
            j+=1
            rows.updateRow(row)

I set the symbology to arrow at end for categories based on OID so that it will be easier to see the separation between features. Labeling was set to count vertices. enter image description here

[GIS] How to add an arrow to a line

Unfortunately you are not the first person to have this problem! A solution is suggested here 3 years ago and indicates the issue has existed since 2002 (and probably earlier). The solution is to use cartographic representations which requires an advanced editor license...

As a possible alternative "fudge" (which I have not tried so not sure of any pitfalls) you could extract the end points of the lines and placing them as a separate layer of markers and rotate them appropriate for each line, this would require you attributing the line with the direction they are pointing.

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