AGP

Completely understand. I took the specific problem of a range circle and tried to generalize it to a range ellipse. I tried to incorporate geodesics to come up with a suitable definition. For my purposes I am trying to minimize the points used in a path finding algorithm. The flatness of the ellipse will determine how "far out" we will search for connection points. Many thanks for your help.

Here are a couple of samples: MIA to ORD BNA to CUN LAX to YYZ

Here are a couple of samples: MIA to ORD BNA to CUN LAX to YYZ

Here are a couple of samples: MIA to ORD BNA to CUN LAX to YYZ

Here are a couple of samples: MIA to ORD BNA to CUN LAX to YYZ

Here is where I am with this challenge. I assume all my coordinates are in WGS84 and the input is ptStart and ptEnd. The I proceed as follows in .NET using the wrapper classes: 'assume a WGS84 datum Dim geod As Geodesic = New Geodesic 'WGS84 Dim s12 As Double, azi1 As Double, azi2 As Double Dim a12 As Double = geod.Inverse(ptStart.Y, ptStart.X, ptEnd.Y, ptEnd.X, s12, azi1, azi2) Dim geoLine As GeodesicLine = New GeodesicLine(geod, ptStart.Y, ptStart.X, azi1, Mask.ALL) 'calculate geodesic distance...

OK let me give this some thought and i will see what I can do with it.

Based on the discussion on range rings from this post https://sourceforge.net/p/geographiclib/discussion/1026621/thread/1df0a86b/ I have been able to recreate geodesic circles that are dead-on when compared to ArcGIS. What I am researching now is how to extend that to "range ellipses". A description here http://desktop.arcgis.com/en/arcmap/10.3/tools/data-management-toolbox/table-to-ellipse.htm. If we take this geodetic ellipse on the surface of the earth and generalize it to have a constant radius...