Tomographic filters for models S20RTS, S40RTS and SP12RTS

Info: Files needed to reparameterise and tomographically filter modelsusing the S**RTS resolution operators following the methodology from Ritsema et al., JGR, 2007. Filters are available to filter S-wave velocity structure up to degree 12 (S12RTS), 20 (S20RTS) or degree 40 (S40RTS), or S-wave and P-wave velocity structure up to degree 12 (SP12RTS). The relevant papers describing the tomographic models are:- S20RTS: Ritsema et al., 1999, Science- S40RTS: Ritsema et al., 2011, GJI- S12RTS / SP12RTS: Koelemeijer et al., 2016, GJI For each model, several files are included:- S**RTS.sph : File containing the model coefficients in spherical harmonics and 21 clamped cubic splines, organised by spline point from the surface to the CMB. - S**RTS.evc : File containing the model eigenvalues and eigenvectors, organised from largest to smallest.- S**RTS.smthp_21 : Auxilliary file containing smoothing parameter values. - header.spt : Auxilliary file containing header info for the joint SP12RTS filter. For SP12RTS, additional model files are made available withdifferent data weighting for normal modes and body waves. - SP12RTS.20.1000.evc : Default version of SP12RTS with mixed data. - SP12RTS.50.100.evc : Version of SP12RTS dominated by body-wave data.- SP12RTS.1.1000.evc : Version of SP12RTS dominated by normal-mode data.