Location interpolation on an ellipsoid

I’m building an application requiring me to consume a set of waypoints as time/lat/lon/alt and interpolate between them. Specifically, a linear interpolation along either a great-circle or a rhumb line connecting the two points.

Browsing orekit and hipparchus, specifically the org.orekit.bodies, org.orekit.models.earth, org.orekit.models.earth.tessellation, and org.hipparchus.geometry.spherical.twod packages, it seems that the while hipparchus provides the underlying mechanisms for great-circle interpolation, rhumbline calculations are absent.

Question #1: Is a rhumbline library an appropriate addition to either hipparchus or orekit? If so, in which library? I lean toward orekit, since my implementation leverages the ellipsoid’s eccentricity and the OneAxisEllipsoid is present in orekit, not hipparchus. But, i’ll defer to those with more experience.

Question #2: For my application, I plan to create a set of PVCoordinatesProvider implementations, backed by either a great-circle or rhumbline interpolation method. Is there any interest in these “waypoint-based” coordinate providers being submitted to orekit? If so, I can develop and create a pull request.

Thanks!

Hi @greyskyy, welcome

You are right, the concept of rhumb line is not implemented at all in either libraries.
There are some new very low level features that may help with the elliptic functions and integrals in Hipparchus, but this has not been extended to paths along the ellipse.

Such an addition would be a good fit into Orekit in my humble opinion. It could also improve the way tesselation is performed currently. Going all the way up to a PVCoordinatesProvider is also interesting, for example if we would like to perform some visibility opportunities with respect to airplane tracks for example in a monitoring or a signal strength computation application.

There is a contribution guide in Orekit website.

Contribution welcome!

Thanks @luc, for the quick reply.

I’ll check out the contribution guide and get a draft MR out there.

–joe

Hi @greyskyy and thanks, I am also interested in this contribution, which allows to define interesting ground paths other than the suborbital track.

I think like @luc that Orekit is the right target for this one because it involves geodetic points on the Earth ellipsoid, which are in Orekit.