svn-gvsig-desktop / tags / v1_10_0_Build_1264 / libraries / libjni-proj4 / src / pj_ell_set.c @ 36455
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/* set ellipsoid parameters a and es */
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#ifndef lint
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static const char SCCSID[]="@(#)pj_ell_set.c 4.5 93/06/12 GIE REL"; |
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#endif
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#include <projects.h> |
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#include <string.h> |
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#define SIXTH .1666666666666666667 /* 1/6 */ |
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#define RA4 .04722222222222222222 /* 17/360 */ |
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#define RA6 .02215608465608465608 /* 67/3024 */ |
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#define RV4 .06944444444444444444 /* 5/72 */ |
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#define RV6 .04243827160493827160 /* 55/1296 */ |
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int /* initialize geographic shape parameters */ |
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pj_ell_set(paralist *pl, double *a, double *es) { |
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int i;
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double b=0.0, e; |
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char *name;
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paralist *start = 0, *curr;
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/* check for varying forms of ellipsoid input */
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*a = *es = 0.;
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/* R takes precedence */
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if (pj_param(pl, "tR").i) |
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*a = pj_param(pl, "dR").f;
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else { /* probable elliptical figure */ |
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/* check if ellps present and temporarily append its values to pl */
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if (name = pj_param(pl, "sellps").s) { |
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char *s;
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for (start = pl; start && start->next ; start = start->next) ;
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curr = start; |
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for (i = 0; (s = pj_ellps[i].id) && strcmp(name, s) ; ++i) ; |
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if (!s) { pj_errno = -9; return 1; } |
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curr = curr->next = pj_mkparam(pj_ellps[i].major); |
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curr = curr->next = pj_mkparam(pj_ellps[i].ell); |
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} |
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*a = pj_param(pl, "da").f;
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if (pj_param(pl, "tes").i) /* eccentricity squared */ |
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*es = pj_param(pl, "des").f;
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else if (pj_param(pl, "te").i) { /* eccentricity */ |
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e = pj_param(pl, "de").f;
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*es = e * e; |
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} else if (pj_param(pl, "trf").i) { /* recip flattening */ |
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*es = pj_param(pl, "drf").f;
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if (!*es) {
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pj_errno = -10;
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goto bomb;
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} |
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*es = 1./ *es;
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*es = *es * (2. - *es);
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} else if (pj_param(pl, "tf").i) { /* flattening */ |
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*es = pj_param(pl, "df").f;
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*es = *es * (2. - *es);
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} else if (pj_param(pl, "tb").i) { /* minor axis */ |
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b = pj_param(pl, "db").f;
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*es = 1. - (b * b) / (*a * *a);
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} /* else *es == 0. and sphere of radius *a */
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if (!b)
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b = *a * sqrt(1. - *es);
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/* following options turn ellipsoid into equivalent sphere */
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if (pj_param(pl, "bR_A").i) { /* sphere--area of ellipsoid */ |
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*a *= 1. - *es * (SIXTH + *es * (RA4 + *es * RA6));
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*es = 0.;
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} else if (pj_param(pl, "bR_V").i) { /* sphere--vol. of ellipsoid */ |
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*a *= 1. - *es * (SIXTH + *es * (RV4 + *es * RV6));
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*es = 0.;
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} else if (pj_param(pl, "bR_a").i) { /* sphere--arithmetic mean */ |
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*a = .5 * (*a + b);
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*es = 0.;
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} else if (pj_param(pl, "bR_g").i) { /* sphere--geometric mean */ |
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*a = sqrt(*a * b); |
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*es = 0.;
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} else if (pj_param(pl, "bR_h").i) { /* sphere--harmonic mean */ |
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*a = 2. * *a * b / (*a + b);
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*es = 0.;
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} else if ((i = pj_param(pl, "tR_lat_a").i) || /* sphere--arith. */ |
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pj_param(pl, "tR_lat_g").i) { /* or geom. mean at latitude */ |
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double tmp;
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tmp = sin(pj_param(pl, i ? "rR_lat_a" : "rR_lat_g").f); |
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if (fabs(tmp) > HALFPI) {
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pj_errno = -11;
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goto bomb;
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} |
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tmp = 1. - *es * tmp * tmp;
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*a *= i ? .5 * (1. - *es + tmp) / ( tmp * sqrt(tmp)) : |
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sqrt(1. - *es) / tmp;
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*es = 0.;
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} |
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bomb:
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if (start) { /* clean up temporary extension of list */ |
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pj_dalloc(start->next->next); |
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pj_dalloc(start->next); |
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start->next = 0;
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} |
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if (pj_errno)
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return 1; |
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} |
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/* some remaining checks */
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if (*es < 0.) |
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{ pj_errno = -12; return 1; } |
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if (*a <= 0.) |
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{ pj_errno = -13; return 1; } |
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return 0; |
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} |