topic Re: Create segment of circle based on point and attribute for radius? in ArcGIS Pro Questions

Create segment of circle based on point and attribute for radius?

David_Brooks — Wed, 06 Apr 2022 21:02:19 GMT

Can anyone suggest a python snippet that could generate a segment of a circle, with the cetnre of the circle defined by a point feature class, and the radius of the segment based on an attribute from the point?

The segment angle can be hard coded, and based on a segment that subtends northwest through to due east.

The reason for this script, is to generate indicative shadow areas for trees, with the radius based on the tree's max height value.

Re: Create segment of circle based on point and attribute for radius?

DanPatterson — Wed, 06 Apr 2022 21:32:55 GMT

sector code

def _arc_sector(radius=100, start=0, stop=1, step=0.1, xc=0.0, yc=0.0): """Create an arc from a specified radius, centre and start/stop angles Requires: --------- `radius` : number cirle radius from which the arc is obtained `start`, `stop`, `step` : numbers angles in degrees `xc`, `yc` : number center coordinates in projected units Returns: -------- points on the arc """ start, stop = sorted([start, stop]) angle = np.deg2rad(np.arange(start, stop, step)) x_s = radius*np.cos(angle) # X values y_s = radius*np.sin(angle) # Y values pnts = np.c_[x_s, y_s] cent = np.array([xc, yc]) pnts = pnts + cent sector = np.concatenate((cent[None, :], pnts, cent[None, :]), axis=0) return sector

example call, it returns a numpy array.

a = _arc_sector(radius=100, start=20, stop=70, step=1, xc=0.0, yc=0.0)

angle from 20 to 70 (relative to N over 0 to 360) in 1 degree steps with center xc, yc)

If you need a list

a_list = a.tolist()

Re: Create segment of circle based on point and attribute for radius?

David_Brooks — Tue, 12 Apr 2022 10:18:06 GMT

@DanPatterson great thank you. So if it generates a numpy array of points, i can use the following to generate a polygon:

a_list = array.tolist() # Create a feature class with a spatial reference of OSGB1936 result = arcpy.management.CreateFeatureclass(r'<GDBLocn>', "TestShadow", "POLYGON", spatial_reference=27700) feature_class = result[0] # Write feature to new feature class with arcpy.da.InsertCursor(feature_class, ['SHAPE@']) as cursor: cursor.insertRow([a_list])

worked a treat. you're a star 🌟

Re: Create segment of circle based on point and attribute for radius?

DanPatterson — Tue, 12 Apr 2022 18:36:01 GMT

glad it worked out!