Arcpy Insert.da.Cursor - Issues writing polygon geometry

Question

Currently building a tool that automates the creation of some polygons that we need done quarterly. Below is just a set script I am using that is giving me a similar issue when I try to run the script. The current output only gives me a polygon with 4 vertices and it is not making a point for each coordinate I have listed. This full script is much larger and complex this is just the one part I am stuck on for some reason. This sample is one of my variations I have tried.

Code

import arcpy

workspace = r"....\Workspace\WritingGeometries"
coordinateSystem = 4326
arcpy.env.workspace = workspace
arcpy.env.overwriteOutput = True
arcpy.env.outputCoordinateSystem = coordinateSystem

fcPointTest = "TestPolygon"
fcPointPath = dsPath + "\\" + fcPointTest
arcpy.CreateFeatureclass_management(dsPath, fcPointTest, "POLYGON")

testCord3 = [arcpy.Point(-95.542806, 30.720361),
             arcpy.Point(-95.479499, 30.805696),
             arcpy.Point(-95.499301, 30.814402),
             arcpy.Point(-95.509831, 30.817513),
             arcpy.Point(-95.516297, 30.818963),
             arcpy.Point(-95.520657, 30.819754),
             arcpy.Point(-95.523791, 30.820232),
             arcpy.Point(-95.526151, 30.820543),
             arcpy.Point(-95.527991, 30.820756),
             arcpy.Point(-95.529465, 30.820909),
             arcpy.Point(-95.530674, 30.821021),
             arcpy.Point(-95.531681, 30.821107),
             arcpy.Point(-95.532535, 30.821174),
             arcpy.Point(-95.533267, 30.821227),
             arcpy.Point(-95.533901, 30.821270),
             arcpy.Point(-95.534457, 30.821305),
             arcpy.Point(-95.542806, 30.821560),
             arcpy.Point(-95.534457, 30.821305),
             arcpy.Point(-95.533901, 30.821270),
             arcpy.Point(-95.533267, 30.821227),
             arcpy.Point(-95.532535, 30.821174),
             arcpy.Point(-95.531681, 30.821107),
             arcpy.Point(-95.530674, 30.821021),
             arcpy.Point(-95.529465, 30.820909),
             arcpy.Point(-95.527991, 30.820756),
             arcpy.Point(-95.526151, 30.820543),
             arcpy.Point(-95.523791, 30.820232),
             arcpy.Point(-95.520657, 30.819754),
             arcpy.Point(-95.516297, 30.818963),
             arcpy.Point(-95.509831, 30.817513),
             arcpy.Point(-95.499301, 30.814402),
             arcpy.Point(-95.606112, 30.805696)]

#Begin Processing
array = arcpy.Array(testCord3)
polygon = arcpy.Polygon(array)
cursor = arcpy.da.InsertCursor(fcPointPath, ["SHAPE@"])
cursor.insertRow([polygon])

del cursor

Below is a screenshot of what my output is.

Solution

Once Paul helped me out and noticed an error in my coordinates I was able to get the script to run through with 0 issues.

Answer 1

Your point locations are what's causing the issue. If you add them in as points, you'll see that 14 of the points are coincident, meaning you are trying to create a polygon part that has 0 area (a line essentially). If you remove all those points, you'll see the result is actually the same.

Don't forget to close your polygons and set the spatial_reference when constructing the Polygon object:

testCord3.append(testCord3[0])
polygon = arcpy.Polygon(array, arcpy.env.outputCoordinateSystem)

Take a look at polygon.getPart(0) and array in your IDE to see what's happening. Nothing wrong with the cursor at all.

Answer 2

I converted your coordinates into a POLYGON in Well-Known Text and got an error (polygon does not close properly), so I added the first point to the end of the point list, and generated this shape:

Then I created a LINESTRING in Well-Known Text and from there into a shapefile and got this:

Then I shifted to POINT and got this (draped over the line, with vertex order labeled):

So it appears that you have a zero-area extension between the third and final vertices, which ArcGIS has "helpfully" removed.

Guidelines for constructing geometry in ArcPy:

• Always extract the SpatialReference from a feature class (this is not the same as a coordinate system) before constructing geometries:

  sr = arcpy.Describe(tabPath).spatialReference

  You can use the SpatialReference used to create the feature class, but then it's wise to specify the origin and units which correspond to your data (in this case, with 6 digits precision, one millionth of a degree)

  sr = arcpy.SpatialReference(4326)

  sr.setFalseOriginAndUnits(-400.0,-400.0,1000000.0)

  but be forewarned that in certain cases, the created feature class may have different parameters than what was requested, so extracting from a Describe is safer.

• Always apply the coordinate reference in the geometry constructor

  polygon = arcpy.Polygon(array,sr)

• Always include the closing point in polygons (yes, ArcGIS, will do it for you, but this may mask issues)

       arcpy.Point(-95.499301, 30.814402),
       arcpy.Point(-95.606112, 30.805696),
       arcpy.Point(-95.542806, 30.720361)]
  

• If something goes wrong, try plotting your coordinates, first as lines, then as points, if necessary, to review correctness.