Automatically Resizing Polygons

MShairah

Hello everyone,

 

I'm currently using ArcGIS 10.5. I was wondering if there is a tool that automatically adjusts a polygon to a specified size? Say I start with a triangle of 3 hectares, and I want to increase its area in all directions for it to become 5 hectares automatically, is there a tool that does this? Or a combination of tools perhaps?

 

Thank you

ESRI_Q1.png

RonaldHaug_0-1716572573341.png

MarkDonnelly

I did come across this bit of code, which may help:

import arcpy
import math

def scale_geom(geom, scale, reference=None):
    """Returns geom scaled to scale %"""
    if geom is None: return None
    if reference is None:
        # we'll use the centroid if no reference point is given
        reference = geom.centroid

    refgeom = arcpy.PointGeometry(reference)
    newparts = []
    for pind in range(geom.partCount):
        part = geom.getPart(pind)
        newpart = []
        for ptind in range(part.count):
            apnt = part.getObject(ptind)
            if apnt is None:
                # polygon boundaries and holes are all returned in the same part.
                # A null point separates each ring, so just pass it on to
                # preserve the holes.
                newpart.append(apnt)
                continue
            bdist = refgeom.distanceTo(apnt)

            bpnt = arcpy.Point(reference.X + bdist, reference.Y)
            adist = refgeom.distanceTo(bpnt)
            cdist = arcpy.PointGeometry(apnt).distanceTo(bpnt)

            # Law of Cosines, angle of C given lengths of a, b and c
            angle = math.acos((adist**2 + bdist**2 - cdist**2) / (2 * adist * bdist))

            scaledist = bdist * scale

            # If the point is below the reference point then our angle
            # is actually negative
            if apnt.Y < reference.Y: angle = angle * -1

            # Create a new point that is scaledist from the origin 
            # along the x axis. Rotate that point the same amount 
            # as the original then translate it to the reference point
            scalex = scaledist * math.cos(angle) + reference.X
            scaley = scaledist * math.sin(angle) + reference.Y

            newpart.append(arcpy.Point(scalex, scaley))
        newparts.append(newpart)

    return arcpy.Geometry(geom.type, arcpy.Array(newparts), geom.spatialReference)

You can call it with a geometry object, a scale factor (1 = same size, 0.5 = half size, 5 = 5 times as large, etc.), and an optional reference point:

scale_geom(some_geom, 1.5)

 Referenced from here:

https://gis.stackexchange.com/questions/169694/is-there-arcpy-tool-for-polygon-resizing-like-scale-tool-of-advanced-editing-too