;+
;
;    property -- a structure containing the following tags.
;            .id            
;            .instru        -- spacecraft & instruments.
;            .hglon         -- longitude in heliographic coordinate.
;            .hglat         -- latitude.
;            .parts         -- how many parts did the prominence split into.
;            .tai_fit_start -- a time in tai format. required when using fitting 
;                              coefficients contained in .data.
;            .cfl           -- averaged confidence level.
;            .data -- an array with parts+1 structures, the first one contain 
;                     the averaged parameters, others for each parts.
;                 .datetime    -- [begin, end]
;                 .duration    -- in hours.
;                 .frames      -- number of data points.
;                 .ismajor     -- indicates this part is a mjaor one or not.
;                 .r_cen       -- heliocentric distance of centroid of brightness, in Mm.
;                                 A 10-element array, first three are [mean, min, max]
;                                 following two are coefficients of linear fitting,
;                                 the sixth one is symbol to indicate if the linear
;                                 fitting is OK (a zero is OK), the seventh through 
;                                 ninth are the coefficients of quadratic fitting, the
;                                 last one indicates if the quadratic fitting succeeded
;                                 (0 menas succeeded).
;                 .p_cen       -- polar angle of centroid of brightness, in degree. 
;                 .r_top       -- heliocentric distance of leading edge, in Mm.
;                 .area        -- in Mm^2.
;                 .length      -- characteristic length, in Mm.
;                 .brightness  -- averaged brightness.
;                 .cfl         -- confidence level
;
;    evolution -- a structure containing variations in time-sequence for the whole prominence
;                 and each part if any.
;             .ids -- change of ids, ptrarr(parts+1), *evolution.ids[i]=strarr(n_frames)
;             .var -- ptrarr(parts+1), *evolution.var[i]=dblarr(11,n_frames), i=0 is for the
;                                      averaged parameters.
;                     (*var[i])[0,*] -- time in tai format.
;                     (*var[i])[1,*] -- heliocentric distance of centroid, in Mm.
;                     (*var[i])[2,*] -- polar angle of centroid, in degree.
;                     (*var[i])[3,*] -- heliocentric distance of leading edge, in Mm.
;                     (*var[i])[4,*] -- heliocentric distance of trailing edge, in Mm.
;                     (*var[i])[5,*] -- minimum of polar angles, in degree.
;                     (*var[i])[6,*] -- maximum of polar angles, in degree.
;                     (*var[i])[7,*] -- area, in Mm^2.
;                     (*var[i])[8,*] -- characteristic length, in Mm.
;                     (*var[i])[9,*] -- brightness.
;                     (*var[i])[10,*] -- confidence level.
;             .ismajor -- a array has parts+1 elements. value is 1 or 0 indicating the 
;                         corresponding part is a major one or not.
;
;History
;    Created by Yuming Wang 2009-12-05.
;
;-