Re: [Orekit Users] Howto: Moving LLA Point Transformation?

[Luc Maisonobe <Luc.Maisonobe@c-s.fr>]

Le 21/08/2015 15:52, Evan Ward a écrit :
> 
> On 08/21/2015 04:24 AM, Luc Maisonobe wrote:
>> Hi James,
>>
>> Le 20/08/2015 22:11, schatzman-james@n-ask.com a écrit :
>>> I can do something like
>>>
>>>             earthRefFrame = getItrfFrame();
>>>             earth = new
>>> OneAxisEllipsoid(Constants.WGS84_EARTH_EQUATORIAL_RADIUS,
>>>                     Constants.WGS84_EARTH_FLATTENING,
>>>                     earthRefFrame);
>>>             TopocentricFrame staF = new TopocentricFrame(earth, lla, "anon");
>>>   PVCoordinates pv = staF.getTransformTo(frame,
>>> dateTime).transformPVCoordinates(      PVCoordinates.ZERO);
>>>
>>>
>>> to compute the position and velocity  in an arbitrary frame corresponding to a
>>> GeodeticPoint lla.
>>>
>>> However, suppose the point is moving in the geodetic frame. There does not
>>> seem to be an analogous class to TopocentricFrame that allows for motion in
>>> the local coordinate system.
>>>
>>> Short of some numerical approximation (e.g. finite differences), how can I
>>> compute the velocity in a new coordinate system of a point moving in LLA?
>> You are right, there were no derivatives associated with GeodeticPoint.
>> I have therefore just added a new signature in the
>> OneAxisEllipsoid.transform method to also provide two double arrays (one
>> for godetic coordinates first derivatives, one for the second
>> derivatives). See
>> <https://www.orekit.org/forge/projects/orekit/repository/revisions/ef1bb1a875f943f478209008c6da94d91848684e>.
>> For now, only the computation from geodetic point to Cartesian is available.
> 
> I think using DerivativeSturctures in the method interface or creating a
> FieldGeodeticPoint<DerivativeStructure> would be a cleaner interface.
> What do you think?

You are right.
I am trying this right now.

Luc

> 
> Best Regards,
> Evan
> 
>> Does this meet your needs?
>>
>> best regards,
>> Luc
>>
>>> Thanks!
>>>
>