[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

*Subject*: Re: spherical harmonics*From*: "John C. Wright" <jwright(at)jwright.physics.wisc.edu>*Date*: Fri, 13 Oct 2000 10:44:05 -0500*In-Reply-To*: <39E6BD56.711C85A6@geo.uni-jena.de>*Newsgroups*: comp.lang.idl-pvwave*Organization*: University of Wisconsin, Madison*References*: <39E6BD56.711C85A6@geo.uni-jena.de>*Reply-To*: "John C. Wright" <johnwright(at)facstaff.wisc.edu>*Xref*: news.doit.wisc.edu comp.lang.idl-pvwave:21697

On Fri, 13 Oct 2000, Klaus Gottschaldt wrote: > Subject: spherical harmonics > > Hallo! > > I want to analyze data on a sphere, representing them by spherical > harmonic coefficients. > This is somehow like a Fourier transform, but based on Legendre > polynoms, which are > defined on the surface of a sphere. > Unlike wavelets, this transform is global. > My data are given in the form [longitude, latitude, data_value], where > longitude, latitude > and data_value are vectors of the same length. > Data points are randomly scattered over the sphere with a resolution of > approx. 100km > on the Earth's surface. > > Does somebody know, how to do this transform with idl? > > Klaus Hi Klaus, I may be in need of such a transform in the near future, also. But for now, the MIDL library has a function, legendre_pol.pro, that returns associated legendre polynomials, then it would be possible to build the transform, though I recognize this would be a bit of work, though the longitudinal transform could be done with IDL's FFT. A word of warning, there are many different Spherical Harmonic decompositions, so make sure your basis functions and normalizations are the same between applications. Let the list know if you find any publicly available solutions, I for one, would be interested. -john

**References**:**spherical harmonics***From:*Klaus Gottschaldt

- Prev by Date:
**Re: spherical harmonics** - Next by Date:
**Mac OS X** - Prev by thread:
**Re: spherical harmonics** - Next by thread:
**Mac OS X** - Index(es):