/src/PROJ/src/projections/igh.cpp

Source


#include <errno.h>
#include <math.h>

#include "proj.h"
#include "proj_internal.h"

PROJ_HEAD(igh, "Interrupted Goode Homolosine") "\n\tPCyl, Sph";

/*
This projection is a compilation of 12 separate sub-projections.
Sinusoidal projections are found near the equator and Mollweide
projections are found at higher latitudes. The transition between
the two occurs at 40 degrees latitude and is represented by the
constant `igh_phi_boundary`.

Each sub-projection is assigned an integer label
numbered 1 through 12. Most of this code contains logic to assign
the labels based on latitude (phi) and longitude (lam) regions.

Original Reference:
J. Paul Goode (1925) THE HOMOLOSINE PROJECTION: A NEW DEVICE FOR
    PORTRAYING THE EARTH'S SURFACE ENTIRE, Annals of the Association of
    American Geographers, 15:3, 119-125, DOI: 10.1080/00045602509356949
*/

C_NAMESPACE PJ *pj_sinu(PJ *), *pj_moll(PJ *);

/*
Transition from sinusoidal to Mollweide projection
Latitude (phi): 40deg 44' 11.8"
*/

constexpr double igh_phi_boundary = (40 + 44 / 60. + 11.8 / 3600.) * DEG_TO_RAD;

namespace pj_igh_ns {
struct pj_igh_data {
    struct PJconsts *pj[12];
    double dy0;
};

constexpr double d10 = 10 * DEG_TO_RAD;
constexpr double d20 = 20 * DEG_TO_RAD;
constexpr double d30 = 30 * DEG_TO_RAD;
constexpr double d40 = 40 * DEG_TO_RAD;
constexpr double d50 = 50 * DEG_TO_RAD;
constexpr double d60 = 60 * DEG_TO_RAD;
constexpr double d80 = 80 * DEG_TO_RAD;
constexpr double d90 = 90 * DEG_TO_RAD;
constexpr double d100 = 100 * DEG_TO_RAD;
constexpr double d140 = 140 * DEG_TO_RAD;
constexpr double d160 = 160 * DEG_TO_RAD;
constexpr double d180 = 180 * DEG_TO_RAD;

constexpr double EPSLN =
    1.e-10; /* allow a little 'slack' on zone edge positions */

} // namespace pj_igh_ns

static PJ_XY igh_s_forward(PJ_LP lp, PJ *P) { /* Spheroidal, forward */
    using namespace pj_igh_ns;
    PJ_XY xy;
    struct pj_igh_data *Q = static_cast<struct pj_igh_data *>(P->opaque);
    int z;

    if (lp.phi >= igh_phi_boundary) { /* 1|2 */
        z = (lp.lam <= -d40 ? 1 : 2);
    } else if (lp.phi >= 0) { /* 3|4 */
        z = (lp.lam <= -d40 ? 3 : 4);
    } else if (lp.phi >= -igh_phi_boundary) { /* 5|6|7|8 */
        if (lp.lam <= -d100)
            z = 5; /* 5 */
        else if (lp.lam <= -d20)
            z = 6; /* 6 */
        else if (lp.lam <= d80)
            z = 7; /* 7 */
        else
            z = 8; /* 8 */
    } else {       /* 9|10|11|12 */
        if (lp.lam <= -d100)
            z = 9; /* 9 */
        else if (lp.lam <= -d20)
            z = 10; /* 10 */
        else if (lp.lam <= d80)
            z = 11; /* 11 */
        else
            z = 12; /* 12 */
    }

    lp.lam -= Q->pj[z - 1]->lam0;
    xy = Q->pj[z - 1]->fwd(lp, Q->pj[z - 1]);
    xy.x += Q->pj[z - 1]->x0;
    xy.y += Q->pj[z - 1]->y0;

    return xy;
}

static PJ_LP igh_s_inverse(PJ_XY xy, PJ *P) { /* Spheroidal, inverse */
    using namespace pj_igh_ns;
    PJ_LP lp = {0.0, 0.0};
    struct pj_igh_data *Q = static_cast<struct pj_igh_data *>(P->opaque);
    const double y90 =
        Q->dy0 + sqrt(2.0); /* lt=90 corresponds to y=y0+sqrt(2) */

    int z = 0;
    if (xy.y > y90 + EPSLN || xy.y < -y90 + EPSLN) /* 0 */
        z = 0;
    else if (xy.y >= igh_phi_boundary) /* 1|2 */
        z = (xy.x <= -d40 ? 1 : 2);
    else if (xy.y >= 0) /* 3|4 */
        z = (xy.x <= -d40 ? 3 : 4);
    else if (xy.y >= -igh_phi_boundary) { /* 5|6|7|8 */
        if (xy.x <= -d100)
            z = 5; /* 5 */
        else if (xy.x <= -d20)
            z = 6; /* 6 */
        else if (xy.x <= d80)
            z = 7; /* 7 */
        else
            z = 8; /* 8 */
    } else {       /* 9|10|11|12 */
        if (xy.x <= -d100)
            z = 9; /* 9 */
        else if (xy.x <= -d20)
            z = 10; /* 10 */
        else if (xy.x <= d80)
            z = 11; /* 11 */
        else
            z = 12; /* 12 */
    }

    if (z) {
        bool ok = false;

        xy.x -= Q->pj[z - 1]->x0;
        xy.y -= Q->pj[z - 1]->y0;
        lp = Q->pj[z - 1]->inv(xy, Q->pj[z - 1]);
        lp.lam += Q->pj[z - 1]->lam0;

        switch (z) {
        case 1:
            ok = (lp.lam >= -d180 - EPSLN && lp.lam <= -d40 + EPSLN) ||
                 ((lp.lam >= -d40 - EPSLN && lp.lam <= -d10 + EPSLN) &&
                  (lp.phi >= d60 - EPSLN && lp.phi <= d90 + EPSLN));
            break;
        case 2:
            ok = (lp.lam >= -d40 - EPSLN && lp.lam <= d180 + EPSLN) ||
                 ((lp.lam >= -d180 - EPSLN && lp.lam <= -d160 + EPSLN) &&
                  (lp.phi >= d50 - EPSLN && lp.phi <= d90 + EPSLN)) ||
                 ((lp.lam >= -d50 - EPSLN && lp.lam <= -d40 + EPSLN) &&
                  (lp.phi >= d60 - EPSLN && lp.phi <= d90 + EPSLN));
            break;
        case 3:
            ok = (lp.lam >= -d180 - EPSLN && lp.lam <= -d40 + EPSLN);
            break;
        case 4:
            ok = (lp.lam >= -d40 - EPSLN && lp.lam <= d180 + EPSLN);
            break;
        case 5:
            ok = (lp.lam >= -d180 - EPSLN && lp.lam <= -d100 + EPSLN);
            break;
        case 6:
            ok = (lp.lam >= -d100 - EPSLN && lp.lam <= -d20 + EPSLN);
            break;
        case 7:
            ok = (lp.lam >= -d20 - EPSLN && lp.lam <= d80 + EPSLN);
            break;
        case 8:
            ok = (lp.lam >= d80 - EPSLN && lp.lam <= d180 + EPSLN);
            break;
        case 9:
            ok = (lp.lam >= -d180 - EPSLN && lp.lam <= -d100 + EPSLN);
            break;
        case 10:
            ok = (lp.lam >= -d100 - EPSLN && lp.lam <= -d20 + EPSLN);
            break;
        case 11:
            ok = (lp.lam >= -d20 - EPSLN && lp.lam <= d80 + EPSLN);
            break;
        case 12:
            ok = (lp.lam >= d80 - EPSLN && lp.lam <= d180 + EPSLN);
            break;
        }
        z = (!ok ? 0 : z); /* projectable? */
    }

    if (!z)
        lp.lam = HUGE_VAL;
    if (!z)
        lp.phi = HUGE_VAL;

    return lp;
}

static PJ *pj_igh_data_destructor(PJ *P, int errlev) {
    using namespace pj_igh_ns;
    int i;
    if (nullptr == P)
        return nullptr;

    if (nullptr == P->opaque)
        return pj_default_destructor(P, errlev);

    struct pj_igh_data *Q = static_cast<struct pj_igh_data *>(P->opaque);

    for (i = 0; i < 12; ++i) {
        if (Q->pj[i])
            Q->pj[i]->destructor(Q->pj[i], errlev);
    }

    return pj_default_destructor(P, errlev);
}

/*
  Zones:

    -180            -40                       180
      +--------------+-------------------------+    Zones 1,2,9,10,11 & 12:
      |1             |2                        |      Mollweide projection
      |              |                         |
      +--------------+-------------------------+    Zones 3,4,5,6,7 & 8:
      |3             |4                        |      Sinusoidal projection
      |              |                         |
    0 +-------+------+-+-----------+-----------+
      |5      |6       |7          |8          |
      |       |        |           |           |
      +-------+--------+-----------+-----------+
      |9      |10      |11         |12         |
      |       |        |           |           |
      +-------+--------+-----------+-----------+
    -180    -100      -20         80          180
*/

static bool pj_igh_setup_zone(PJ *P, struct pj_igh_ns::pj_igh_data *Q, int n,
                              PJ *(*proj_ptr)(PJ *), double x_0, double y_0,
                              double lon_0) {
    if (!(Q->pj[n - 1] = proj_ptr(nullptr)))
        return false;
    if (!(Q->pj[n - 1] = proj_ptr(Q->pj[n - 1])))
        return false;
    Q->pj[n - 1]->ctx = P->ctx;
    Q->pj[n - 1]->x0 = x_0;
    Q->pj[n - 1]->y0 = y_0;
    Q->pj[n - 1]->lam0 = lon_0;
    return true;
}

PJ *PJ_PROJECTION(igh) {
    using namespace pj_igh_ns;

    PJ_XY xy1, xy3;
    PJ_LP lp = {0, igh_phi_boundary};
    struct pj_igh_data *Q = static_cast<struct pj_igh_data *>(
        calloc(1, sizeof(struct pj_igh_data)));
    if (nullptr == Q)
        return pj_default_destructor(P, PROJ_ERR_OTHER /*ENOMEM*/);
    P->opaque = Q;

    /* sinusoidal zones */
    if (!pj_igh_setup_zone(P, Q, 3, pj_sinu, -d100, 0, -d100) ||
        !pj_igh_setup_zone(P, Q, 4, pj_sinu, d30, 0, d30) ||
        !pj_igh_setup_zone(P, Q, 5, pj_sinu, -d160, 0, -d160) ||
        !pj_igh_setup_zone(P, Q, 6, pj_sinu, -d60, 0, -d60) ||
        !pj_igh_setup_zone(P, Q, 7, pj_sinu, d20, 0, d20) ||
        !pj_igh_setup_zone(P, Q, 8, pj_sinu, d140, 0, d140)) {
        return pj_igh_data_destructor(P, PROJ_ERR_OTHER /*ENOMEM*/);
    }

    /* mollweide zones */
    if (!pj_igh_setup_zone(P, Q, 1, pj_moll, -d100, 0, -d100)) {
        return pj_igh_data_destructor(P, PROJ_ERR_OTHER /*ENOMEM*/);
    }

    /* y0 ? */
    xy1 = Q->pj[0]->fwd(lp, Q->pj[0]); /* zone 1 */
    xy3 = Q->pj[2]->fwd(lp, Q->pj[2]); /* zone 3 */
    /* y0 + xy1.y = xy3.y for lt = 40d44'11.8" */
    Q->dy0 = xy3.y - xy1.y;

    Q->pj[0]->y0 = Q->dy0;

    /* mollweide zones (cont'd) */
    if (!pj_igh_setup_zone(P, Q, 2, pj_moll, d30, Q->dy0, d30) ||
        !pj_igh_setup_zone(P, Q, 9, pj_moll, -d160, -Q->dy0, -d160) ||
        !pj_igh_setup_zone(P, Q, 10, pj_moll, -d60, -Q->dy0, -d60) ||
        !pj_igh_setup_zone(P, Q, 11, pj_moll, d20, -Q->dy0, d20) ||
        !pj_igh_setup_zone(P, Q, 12, pj_moll, d140, -Q->dy0, d140)) {
        return pj_igh_data_destructor(P, PROJ_ERR_OTHER /*ENOMEM*/);
    }

    P->inv = igh_s_inverse;
    P->fwd = igh_s_forward;
    P->destructor = pj_igh_data_destructor;
    P->es = 0.;

    return P;
}

Coverage Report

Created: 2025-11-09 06:51

Line	Count	Source
1
2
3		#include <errno.h>
4		#include <math.h>
5
6		#include "proj.h"
7		#include "proj_internal.h"
8
9		PROJ_HEAD(igh, "Interrupted Goode Homolosine") "\n\tPCyl, Sph";
10
11		/*
12		This projection is a compilation of 12 separate sub-projections.
13		Sinusoidal projections are found near the equator and Mollweide
14		projections are found at higher latitudes. The transition between
15		the two occurs at 40 degrees latitude and is represented by the
16		constant `igh_phi_boundary`.
17
18		Each sub-projection is assigned an integer label
19		numbered 1 through 12. Most of this code contains logic to assign
20		the labels based on latitude (phi) and longitude (lam) regions.
21
22		Original Reference:
23		J. Paul Goode (1925) THE HOMOLOSINE PROJECTION: A NEW DEVICE FOR
24		PORTRAYING THE EARTH'S SURFACE ENTIRE, Annals of the Association of
25		American Geographers, 15:3, 119-125, DOI: 10.1080/00045602509356949
26		*/
27
28		C_NAMESPACE PJ pj_sinu(PJ ), pj_moll(PJ );
29
30		/*
31		Transition from sinusoidal to Mollweide projection
32		Latitude (phi): 40deg 44' 11.8"
33		*/
34
35		constexpr double igh_phi_boundary = (40 + 44 / 60. + 11.8 / 3600.) * DEG_TO_RAD;
36
37		namespace pj_igh_ns {
38		struct pj_igh_data {
39		struct PJconsts *pj[12];
40		double dy0;
41		};
42
43		constexpr double d10 = 10 * DEG_TO_RAD;
44		constexpr double d20 = 20 * DEG_TO_RAD;
45		constexpr double d30 = 30 * DEG_TO_RAD;
46		constexpr double d40 = 40 * DEG_TO_RAD;
47		constexpr double d50 = 50 * DEG_TO_RAD;
48		constexpr double d60 = 60 * DEG_TO_RAD;
49		constexpr double d80 = 80 * DEG_TO_RAD;
50		constexpr double d90 = 90 * DEG_TO_RAD;
51		constexpr double d100 = 100 * DEG_TO_RAD;
52		constexpr double d140 = 140 * DEG_TO_RAD;
53		constexpr double d160 = 160 * DEG_TO_RAD;
54		constexpr double d180 = 180 * DEG_TO_RAD;
55
56		constexpr double EPSLN =
57		1.e-10; /* allow a little 'slack' on zone edge positions */
58
59		} // namespace pj_igh_ns
60
61	2.52k	static PJ_XY igh_s_forward(PJ_LP lp, PJ P) { / Spheroidal, forward */
62	2.52k	using namespace pj_igh_ns;
63	2.52k	PJ_XY xy;
64	2.52k	struct pj_igh_data Q = static_cast<struct pj_igh_data >(P->opaque);
65	2.52k	int z;
66
67	2.52k	if (lp.phi >= igh_phi_boundary) { /* 1\|2 */
68	924	z = (lp.lam <= -d40 ? 1 : 2);
69	1.59k	} else if (lp.phi >= 0) { /* 3\|4 */
70	1.59k	z = (lp.lam <= -d40 ? 3 : 4);
71	1.59k	} else if (lp.phi >= -igh_phi_boundary) { /* 5\|6\|7\|8 */
72	0	if (lp.lam <= -d100)
73	0	z = 5; /* 5 */
74	0	else if (lp.lam <= -d20)
75	0	z = 6; /* 6 */
76	0	else if (lp.lam <= d80)
77	0	z = 7; /* 7 */
78	0	else
79	0	z = 8; /* 8 */
80	0	} else { /* 9\|10\|11\|12 */
81	0	if (lp.lam <= -d100)
82	0	z = 9; /* 9 */
83	0	else if (lp.lam <= -d20)
84	0	z = 10; /* 10 */
85	0	else if (lp.lam <= d80)
86	0	z = 11; /* 11 */
87	0	else
88	0	z = 12; /* 12 */
89	0	}
90
91	2.52k	lp.lam -= Q->pj[z - 1]->lam0;
92	2.52k	xy = Q->pj[z - 1]->fwd(lp, Q->pj[z - 1]);
93	2.52k	xy.x += Q->pj[z - 1]->x0;
94	2.52k	xy.y += Q->pj[z - 1]->y0;
95
96	2.52k	return xy;
97	2.52k	}
98
99	0	static PJ_LP igh_s_inverse(PJ_XY xy, PJ P) { / Spheroidal, inverse */
100	0	using namespace pj_igh_ns;
101	0	PJ_LP lp = {0.0, 0.0};
102	0	struct pj_igh_data Q = static_cast<struct pj_igh_data >(P->opaque);
103	0	const double y90 =
104	0	Q->dy0 + sqrt(2.0); /* lt=90 corresponds to y=y0+sqrt(2) */
105
106	0	int z = 0;
107	0	if (xy.y > y90 + EPSLN \|\| xy.y < -y90 + EPSLN) /* 0 */
108	0	z = 0;
109	0	else if (xy.y >= igh_phi_boundary) /* 1\|2 */
110	0	z = (xy.x <= -d40 ? 1 : 2);
111	0	else if (xy.y >= 0) /* 3\|4 */
112	0	z = (xy.x <= -d40 ? 3 : 4);
113	0	else if (xy.y >= -igh_phi_boundary) { /* 5\|6\|7\|8 */
114	0	if (xy.x <= -d100)
115	0	z = 5; /* 5 */
116	0	else if (xy.x <= -d20)
117	0	z = 6; /* 6 */
118	0	else if (xy.x <= d80)
119	0	z = 7; /* 7 */
120	0	else
121	0	z = 8; /* 8 */
122	0	} else { /* 9\|10\|11\|12 */
123	0	if (xy.x <= -d100)
124	0	z = 9; /* 9 */
125	0	else if (xy.x <= -d20)
126	0	z = 10; /* 10 */
127	0	else if (xy.x <= d80)
128	0	z = 11; /* 11 */
129	0	else
130	0	z = 12; /* 12 */
131	0	}
132
133	0	if (z) {
134	0	bool ok = false;
135
136	0	xy.x -= Q->pj[z - 1]->x0;
137	0	xy.y -= Q->pj[z - 1]->y0;
138	0	lp = Q->pj[z - 1]->inv(xy, Q->pj[z - 1]);
139	0	lp.lam += Q->pj[z - 1]->lam0;
140
141	0	switch (z) {
142	0	case 1:
143	0	ok = (lp.lam >= -d180 - EPSLN && lp.lam <= -d40 + EPSLN) \|\|
144	0	((lp.lam >= -d40 - EPSLN && lp.lam <= -d10 + EPSLN) &&
145	0	(lp.phi >= d60 - EPSLN && lp.phi <= d90 + EPSLN));
146	0	break;
147	0	case 2:
148	0	ok = (lp.lam >= -d40 - EPSLN && lp.lam <= d180 + EPSLN) \|\|
149	0	((lp.lam >= -d180 - EPSLN && lp.lam <= -d160 + EPSLN) &&
150	0	(lp.phi >= d50 - EPSLN && lp.phi <= d90 + EPSLN)) \|\|
151	0	((lp.lam >= -d50 - EPSLN && lp.lam <= -d40 + EPSLN) &&
152	0	(lp.phi >= d60 - EPSLN && lp.phi <= d90 + EPSLN));
153	0	break;
154	0	case 3:
155	0	ok = (lp.lam >= -d180 - EPSLN && lp.lam <= -d40 + EPSLN);
156	0	break;
157	0	case 4:
158	0	ok = (lp.lam >= -d40 - EPSLN && lp.lam <= d180 + EPSLN);
159	0	break;
160	0	case 5:
161	0	ok = (lp.lam >= -d180 - EPSLN && lp.lam <= -d100 + EPSLN);
162	0	break;
163	0	case 6:
164	0	ok = (lp.lam >= -d100 - EPSLN && lp.lam <= -d20 + EPSLN);
165	0	break;
166	0	case 7:
167	0	ok = (lp.lam >= -d20 - EPSLN && lp.lam <= d80 + EPSLN);
168	0	break;
169	0	case 8:
170	0	ok = (lp.lam >= d80 - EPSLN && lp.lam <= d180 + EPSLN);
171	0	break;
172	0	case 9:
173	0	ok = (lp.lam >= -d180 - EPSLN && lp.lam <= -d100 + EPSLN);
174	0	break;
175	0	case 10:
176	0	ok = (lp.lam >= -d100 - EPSLN && lp.lam <= -d20 + EPSLN);
177	0	break;
178	0	case 11:
179	0	ok = (lp.lam >= -d20 - EPSLN && lp.lam <= d80 + EPSLN);
180	0	break;
181	0	case 12:
182	0	ok = (lp.lam >= d80 - EPSLN && lp.lam <= d180 + EPSLN);
183	0	break;
184	0	}
185	0	z = (!ok ? 0 : z); /* projectable? */
186	0	}
187
188	0	if (!z)
189	0	lp.lam = HUGE_VAL;
190	0	if (!z)
191	0	lp.phi = HUGE_VAL;
192
193	0	return lp;
194	0	}
195
196	68	static PJ pj_igh_data_destructor(PJ P, int errlev) {
197	68	using namespace pj_igh_ns;
198	68	int i;
199	68	if (nullptr == P)
200	0	return nullptr;
201
202	68	if (nullptr == P->opaque)
203	0	return pj_default_destructor(P, errlev);
204
205	68	struct pj_igh_data Q = static_cast<struct pj_igh_data >(P->opaque);
206
207	884	for (i = 0; i < 12; ++i) {
208	816	if (Q->pj[i])
209	816	Q->pj[i]->destructor(Q->pj[i], errlev);
210	816	}
211
212	68	return pj_default_destructor(P, errlev);
213	68	}
214
215		/*
216		Zones:
217
218		-180 -40 180
219		+--------------+-------------------------+ Zones 1,2,9,10,11 & 12:
220		\|1 \|2 \| Mollweide projection
221		\| \| \|
222		+--------------+-------------------------+ Zones 3,4,5,6,7 & 8:
223		\|3 \|4 \| Sinusoidal projection
224		\| \| \|
225		0 +-------+------+-+-----------+-----------+
226		\|5 \|6 \|7 \|8 \|
227		\| \| \| \| \|
228		+-------+--------+-----------+-----------+
229		\|9 \|10 \|11 \|12 \|
230		\| \| \| \| \|
231		+-------+--------+-----------+-----------+
232		-180 -100 -20 80 180
233		*/
234
235		static bool pj_igh_setup_zone(PJ P, struct pj_igh_ns::pj_igh_data Q, int n,
236		PJ (proj_ptr)(PJ *), double x_0, double y_0,
237	816	double lon_0) {
238	816	if (!(Q->pj[n - 1] = proj_ptr(nullptr)))
239	0	return false;
240	816	if (!(Q->pj[n - 1] = proj_ptr(Q->pj[n - 1])))
241	0	return false;
242	816	Q->pj[n - 1]->ctx = P->ctx;
243	816	Q->pj[n - 1]->x0 = x_0;
244	816	Q->pj[n - 1]->y0 = y_0;
245	816	Q->pj[n - 1]->lam0 = lon_0;
246	816	return true;
247	816	}
248
249	68	PJ *PJ_PROJECTION(igh) {
250	68	using namespace pj_igh_ns;
251
252	68	PJ_XY xy1, xy3;
253	68	PJ_LP lp = {0, igh_phi_boundary};
254	68	struct pj_igh_data Q = static_cast<struct pj_igh_data >(
255	68	calloc(1, sizeof(struct pj_igh_data)));
256	68	if (nullptr == Q)
257	0	return pj_default_destructor(P, PROJ_ERR_OTHER /ENOMEM/);
258	68	P->opaque = Q;
259
260		/* sinusoidal zones */
261	68	if (!pj_igh_setup_zone(P, Q, 3, pj_sinu, -d100, 0, -d100) \|\|
262	68	!pj_igh_setup_zone(P, Q, 4, pj_sinu, d30, 0, d30) \|\|
263	68	!pj_igh_setup_zone(P, Q, 5, pj_sinu, -d160, 0, -d160) \|\|
264	68	!pj_igh_setup_zone(P, Q, 6, pj_sinu, -d60, 0, -d60) \|\|
265	68	!pj_igh_setup_zone(P, Q, 7, pj_sinu, d20, 0, d20) \|\|
266	68	!pj_igh_setup_zone(P, Q, 8, pj_sinu, d140, 0, d140)) {
267	0	return pj_igh_data_destructor(P, PROJ_ERR_OTHER /ENOMEM/);
268	0	}
269
270		/* mollweide zones */
271	68	if (!pj_igh_setup_zone(P, Q, 1, pj_moll, -d100, 0, -d100)) {
272	0	return pj_igh_data_destructor(P, PROJ_ERR_OTHER /ENOMEM/);
273	0	}
274
275		/* y0 ? */
276	68	xy1 = Q->pj[0]->fwd(lp, Q->pj[0]); /* zone 1 */
277	68	xy3 = Q->pj[2]->fwd(lp, Q->pj[2]); /* zone 3 */
278		/* y0 + xy1.y = xy3.y for lt = 40d44'11.8" */
279	68	Q->dy0 = xy3.y - xy1.y;
280
281	68	Q->pj[0]->y0 = Q->dy0;
282
283		/* mollweide zones (cont'd) */
284	68	if (!pj_igh_setup_zone(P, Q, 2, pj_moll, d30, Q->dy0, d30) \|\|
285	68	!pj_igh_setup_zone(P, Q, 9, pj_moll, -d160, -Q->dy0, -d160) \|\|
286	68	!pj_igh_setup_zone(P, Q, 10, pj_moll, -d60, -Q->dy0, -d60) \|\|
287	68	!pj_igh_setup_zone(P, Q, 11, pj_moll, d20, -Q->dy0, d20) \|\|
288	68	!pj_igh_setup_zone(P, Q, 12, pj_moll, d140, -Q->dy0, d140)) {
289	0	return pj_igh_data_destructor(P, PROJ_ERR_OTHER /ENOMEM/);
290	0	}
291
292	68	P->inv = igh_s_inverse;
293	68	P->fwd = igh_s_forward;
294	68	P->destructor = pj_igh_data_destructor;
295	68	P->es = 0.;
296
297	68	return P;
298	68	}