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.


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.


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.

MR is here: Interpolated-waypoint PVCoordinatesProvider (!275) · Merge requests · Orekit / Orekit · GitLab let me know what you think.

Thank you so much!
We will be looking at this soon.
As this contribution is quite large, we will need some paperwork so we can publish it. Please have a look at the governance, chapter 3. There are two different kinds of paper you could use, the choice belongs to you. The first kind are contributor license agreements (either individual or corporate), it is intended when people are willing to contribute regularly, as they cover every work one identified person is willing to contribute. The second kind is software grant, it is intended for single time contributions, and in this case the grant reference explicitly the work.
Basically, in both cases, the paper state that the contributor grants us a license to publish the work to the rest of the world under the terms of the Apache License. There are no copyright transfers, the intellectual property rights remain the sole property of the original contributor.
Of course, as these papers are official and contains names and signatures, you should send them to us (a scanned PDF is OK) using private messaging in order not to expose your personal data.

Thanks again for this contribution!

Just checking in @luc. do you have everything you all need to review MR!275?

I know it’s a sizable MR, so I understand taking the time to review. Just checking to be sure it’s no longer waiting in data from me.


Hi Joe,

Don’t worry, I think we have everything we need.
I am just busy doing other things, so it may take some time to be merged.

Hi Joe,

We are very sorry for the delay…
@pascal.parraud has an intern working on a close topic. I believe his intern is reviewing the MR.
Pascal, can you confirm?


thank for the update @luc and @bcazabonne . I just hadn’t heard anything in a while and wanted to be sure there wasn’t a required update on my end holding things up.

Appreciate the review time.

Hi @greyskyy,
Your merge request has been merged.
Thank you again for your contribution.