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Oriented buffers

davesacco

Hi there,

I am using arcview 9.3.1 and I need to create oriented buffers from points in a shapefile. The euclidean direction method almost works, but because it calculates to the nearest point, buffers associated with points within the maximum will be truncated. I need each point to have a complete buffer in a specific direction, regardless of overlap with other points.

Any ideas would be greatly appreciated.

Thanks,

Dave

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Accepted answers

XanderBakker

As promised...

The code below will create the circle sectors based on the point location and 3 additional columns:

one for the start angle
one for the end angle
and the distance (size)

The angles are expressed arithmetically:

In your case you will want to use start = 180° and end = 225°

I used random points, with random angles and random sizes and this was the result:

This is the code I used:

#-------------------------------------------------------------------------------
# Name:        createSectors.py
# Purpose:    create circle sectors for points
#
# Author:      Xander
#
# Created:    08-02-2015
#-------------------------------------------------------------------------------
import arcpy

def main():
    fc_in = r"C:\Forum\CircleSectors\data.gdb\points2"
    fc_out = r"C:\Forum\CircleSectors\data.gdb\sectors2"

    fld_start = "StartAngle"
    fld_end = "EndAngle"
    fld_dist = "Length"

    sr = arcpy.Describe(fc_in).spatialReference
    arcpy.env.overwriteOutput = True

    flds = ("SHAPE@", fld_start, fld_end, fld_dist)
    lst_polygons = []
    with arcpy.da.SearchCursor(fc_in, flds) as curs:
        for row in curs:
            pnt_g = row[0]
            start = row[1]
            end = row[2]
            length = row[3]
            circle = pnt_g.buffer(length)
            pnt = pnt_g.firstPoint
            arrPnts = arcpy.Array()
            arrPnts.add(pnt)
            for bearing in range(int(start), int(end) + 1):
                arrPnts.add(createPointAtAngleWithBearing(pnt, bearing, length))
            polygon = arcpy.Polygon(arrPnts, sr)
            lst_polygons.append(polygon)

    arcpy.CopyFeatures_management(lst_polygons, fc_out)

def createPointAtAngleWithBearing(pnt, angle, distance):
    import math
    angle = math.radians(angle)
    dist_x, dist_y = (distance * math.cos(angle), distance * math.sin(angle))
    return arcpy.Point(pnt.X + dist_x, pnt.Y + dist_y)

if __name__ == '__main__':
    main()

Kind regards, Xander

All comments

DarrenWiens2

It may be having issues with escape characters in the lines where you specify the paths. Try adding an 'r' to denote raw string notation:

e.g.

fc_in <SPAN class="operator token">=</SPAN> r<SPAN class="string token">"C:\Users\ihwm\Documents\ArcGIS\Flood_NT_WA.gdb\points"</SPAN><SPAN class="line-numbers-rows"><SPAN>‍</SPAN></SPAN>

Hayley_DelMaynard

Thanks Dan. I really appreciate the quick response. I changed the lines to include the field names, but I still receive the below error message:

Runtime error
Traceback (most recent call last):
File "<string>", line 40, in <module>
File "<string>", line 11, in main
AttributeError: DescribeData: Method spatialReference does not exist

>>> import arcpy
...
... def main():
... fc_in = "C:\Users\ihwm\Documents\ArcGIS\Flood_NT_WA.gdb\points"
... fc_out = "C:\Users\ihwm\Documents\ArcGIS\Flood_NT_WA.gdb\points2"
...
... fld_start = "fld_start"
... fld_end = "fld_end"
... fld_dist = "fld_dist"
...
... sr = arcpy.Describe(fc_in).spatialReference
... arcpy.env.overwriteOutput = True
...
... flds = ("SHAPE@", fld_start, fld_end, fld_dist)
... lst_polygons = [1]
... with arcpy.da.SearchCursor(fc_in, flds) as curs:
... for row in curs:
... pnt_g = row[0]
... start = row[1]
... end = row[2]
... length = row[3]
... circle = pnt_g.buffer(length)
... pnt = pnt_g.firstPoint
... arrPnts = arcpy.Array()
... arrPnts.add(pnt)
... for bearing in range(int(start), int(end) + 1):
... arrPnts.add(createPointAtAngleWithBearing(pnt, bearing, length))
... polygon = arcpy.Polygon(arrPnts, sr)
... lst_polygons.append(polygon)
...
... arcpy.CopyFeatures_management(lst_polygons, fc_out)
...
... def createPointAtAngleWithBearing(pnt, angle, distance):
... import math
... angle = math.radians(angle)
... dist_x, dist_y = (distance * math.cos(angle), distance * math.sin(angle))
... return arcpy.Point(pnt.X + dist_x, pnt.Y + dist_y)
...
... if __name__ == '__main__':
... main()
...
Runtime error
Traceback (most recent call last):
File "<string>", line 40, in <module>
File "<string>", line 11, in main
AttributeError: DescribeData: Method spatialReference does not exist

DanPatterson_Retired

flds = ("SHAPE@", fld_start, fld_end, fld_dist)

for the last 3, you provided numbers rather than the field names that contained the values

Hayley_DelMaynard

Xander Bakker‌ Thanks so much for this! I'm trying to create 4 90degree buffers around all points in my data frame. I tried using your code and I keep getting this below error. I'm pretty new to Python, do you know how to fix this? Thanks again!

>>> import arcpy
...
... def main():
... fc_in = "C:\Users\A0701216\Documents\ArcGIS\Default.gdb\ALEX"
... fc_out = "C:\Users\A0701216\Documents\ArcGIS\Default.gdb\ALEX_"
...
... fld_start = 180
... fld_end = 225
... fld_dist = 15
...
... sr = arcpy.Describe(fc_in).spatialReference
... arcpy.env.overwriteOutput = True
...
... flds = ("SHAPE@", fld_start, fld_end, fld_dist)
... lst_polygons = [1]
... with arcpy.da.SearchCursor(fc_in, flds) as curs:
... for row in curs:
... pnt_g = row[0]
... start = row[1]
... end = row[2]
... length = row[3]
... circle = pnt_g.buffer(length)
... pnt = pnt_g.firstPoint
... arrPnts = arcpy.Array()
... arrPnts.add(pnt)
... for bearing in range(int(start), int(end) + 1):
... arrPnts.add(createPointAtAngleWithBearing(pnt, bearing, length))
... polygon = arcpy.Polygon(arrPnts, sr)
... lst_polygons.append(polygon)
...
... arcpy.CopyFeatures_management(lst_polygons, fc_out)
...
... def createPointAtAngleWithBearing(pnt, angle, distance):
... import math
... angle = math.radians(angle)
... dist_x, dist_y = (distance * math.cos(angle), distance * math.sin(angle))
... return arcpy.Point(pnt.X + dist_x, pnt.Y + dist_y)
...
... if __name__ == '__main__':
... main()
...
Runtime error
Traceback (most recent call last):
File "<string>", line 40, in <module>
File "<string>", line 16, in main
TypeError: 'field_names' must be string or non empty sequence of strings
>>>

XanderBakker

LOL, it's actually a very nice a simple way of getting the result... So no harm done, thanks for contributing this solution, Darren Wiens‌ and yes I think this would answer the question.

I will however start with a more generic solution that allows for setting the start angle, end angle and distance for each sector and will share it later on.

DarrenWiens2

Here's how you can do this using arcpy and geometry objects:

>>> radius = 200000 # buffer radius
>>> polys = []
>>> sr = arcpy.Describe("YOUR_POINT_LAYER_NAME_HERE").spatialReference
>>> with arcpy.da.SearchCursor("YOUR_POINT_LAYER_NAME_HERE","SHAPE@",'#',sr) as cursor:
...     for row in cursor:
...         pt1 = row[0].centroid
...         pt2 = arcpy.Point(row[0].centroid.X - radius*2, row[0].centroid.Y)
...         pt3 = arcpy.Point(row[0].centroid.X - radius*2, row[0].centroid.Y - radius*2)
...         triangle = arcpy.Polygon(arcpy.Array([pt1,pt2,pt3]),sr)
...         buffer = row[0].buffer(radius)
...         wedge = triangle.intersect(buffer,4)
...         polys.append(wedge)
...         
>>> arcpy.CopyFeatures_management(polys,'in_memory\wedges')
<Result 'in_memory\\wedges'>

It helps that all wedges are the same shape, so the triangle shape used to clip (intersect) the buffer is hard-coded. You could fairly easily alter the script to respond to attribute data.

Sorry for swooping in on your fun, Xander

davesacco

Hi Xander,

Thanks for taking the time to help out. I'll try this tool out, but I need a different shape so it may not be the solution. I'll attach an image from the euclidean direction tool that will hopefully make this a bit clearer. Without getting into too much detail, I need to illustrate an area that may be a source for the point data. In the attached image, the transport direction ranges from 45-90 degrees, hence the cone shape (the transport vectors vary throughout the data set). My only issue is the truncation in the raster due to the close points. I.e, they need to overlap.

Another idea is to somehow generate 2 lines at specified azimuths from the points and then use them to intersect with a buffer around the point. This would allow for the overlap that the raster does not accommodate.

Pretty stumped right now, so I really appreciate your input and time.

Dave

XanderBakker

Would the table to ellipse tool be of any help?

ArcGIS Help (10.2, 10.2.1, and 10.2.2)

If not a picture to show what you are after would help.

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