Hi need some help in how to find the long axis of an irregular shaped ellipse using ArcGIS. I have found the centroid but don't know how to determine the longest distance.
You can use the Minimum Bounding Geometry (Data Management) tool.
Use the 'Convex Hull' option.
This will create several new fields:
MBG_Length will give you the distance between the farthest points (antipodes)
The MBG_APOD points will give you the coordinates of the new antipodal line