Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Fix imoll and imoll_o zone calculations to correct inverse transformations near the "seams". #4159

Merged
merged 4 commits into from
Jun 3, 2024
Merged

Fix imoll and imoll_o zone calculations to correct inverse transformations near the "seams". #4159

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
58d7fdd
Fix x zone boundaries when doing inverse imoll transform.
erykoff Jun 2, 2024
43470c7
Fix x zone boundaries when doing inverse imoll_o transform.
erykoff Jun 2, 2024
2b8d75b
Add roundtrip tests for imoll near the "seams".
erykoff Jun 2, 2024
f90af2e
Add roundtrip tests for imoll_o near the "seams".
erykoff Jun 2, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
36 changes: 32 additions & 4 deletions src/projections/imoll.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -30,6 +30,11 @@ C_NAMESPACE PJ *pj_moll(PJ *);
namespace pj_imoll_ns {
struct pj_imoll_data {
struct PJconsts *pj[6];
// We need to know the inverse boundary locations of the "seams".
double boundary12;
double boundary34;
double boundary45;
double boundary56;
};

constexpr double d20 = 20 * DEG_TO_RAD;
Expand Down Expand Up @@ -92,13 +97,13 @@ static PJ_LP imoll_s_inverse(PJ_XY xy, PJ *P) { /* Spheroidal, inverse */
if (xy.y > y90 + EPSLN || xy.y < -y90 + EPSLN) /* 0 */
z = 0;
else if (xy.y >= 0)
z = (xy.x <= -d40 ? 1 : 2); /* 1|2 */
z = (xy.x <= (Q->boundary12) ? 1 : 2); /* 1|2 */
else {
if (xy.x <= -d100)
if (xy.x <= Q->boundary34)
z = 3; /* 3 */
else if (xy.x <= -d20)
else if (xy.x <= Q->boundary45)
z = 4; /* 4 */
else if (xy.x <= d80)
else if (xy.x <= Q->boundary56)
z = 5; /* 5 */
else
z = 6; /* 6 */
Expand Down Expand Up @@ -218,6 +223,19 @@ static double compute_zone_offset(struct pj_imoll_ns::pj_imoll_data *Q,
return (xy2.x + Q->pj[zone2 - 1]->x0) - (xy1.x + Q->pj[zone1 - 1]->x0);
}

static double compute_zone_x_boundary(PJ *P, double lam, double phi) {
PJ_LP lp1, lp2;
PJ_XY xy1, xy2;

lp1.lam = lam - pj_imoll_ns::EPSLN;
lp1.phi = phi;
lp2.lam = lam + pj_imoll_ns::EPSLN;
lp2.phi = phi;
xy1 = imoll_s_forward(lp1, P);
xy2 = imoll_s_forward(lp2, P);
return (xy1.x + xy2.x)/2.;
}

PJ *PJ_PROJECTION(imoll) {
using namespace pj_imoll_ns;

Expand Down Expand Up @@ -258,6 +276,16 @@ PJ *PJ_PROJECTION(imoll) {
/* Match 6 (south) to 2 (north) */
Q->pj[5]->x0 += compute_zone_offset(Q, 6, 2, d80, 0.0 - EPSLN, 0.0 + EPSLN);

/*
The most straightforward way of computing the x locations of the "seams"
in the interrupted projection is to compute the forward transform at the
seams and record these values.
*/
Q->boundary12 = compute_zone_x_boundary(P, -d40, 0.0 + EPSLN);
Q->boundary34 = compute_zone_x_boundary(P, -d100, 0.0 - EPSLN);
Q->boundary45 = compute_zone_x_boundary(P, -d20, 0.0 - EPSLN);
Q->boundary56 = compute_zone_x_boundary(P, d80, 0.0 - EPSLN);

P->inv = imoll_s_inverse;
P->fwd = imoll_s_forward;
P->destructor = pj_imoll_destructor;
Expand Down
37 changes: 33 additions & 4 deletions src/projections/imoll_o.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,11 @@ C_NAMESPACE PJ *pj_moll(PJ *);
namespace pj_imoll_o_ns {
struct pj_imoll_o_data {
struct PJconsts *pj[6];
// We need to know the inverse boundary locations of the "seams".
double boundary12;
double boundary23;
double boundary45;
double boundary56;
};

/* SIMPLIFY THIS */
Expand Down Expand Up @@ -100,16 +105,16 @@ static PJ_LP imoll_o_s_inverse(PJ_XY xy, PJ *P) { /* Spheroidal, inverse */
if (xy.y > y90 + EPSLN || xy.y < -y90 + EPSLN) /* 0 */
z = 0;
else if (xy.y >= 0) {
if (xy.x <= -d90)
if (xy.x <= Q->boundary12)
z = 1;
else if (xy.x >= d60)
else if (xy.x >= Q->boundary23)
z = 3;
else
z = 2;
} else {
if (xy.x <= -d60)
if (xy.x <= Q->boundary45)
z = 4;
else if (xy.x >= d90)
else if (xy.x >= Q->boundary56)
z = 6;
else
z = 5;
Expand Down Expand Up @@ -232,6 +237,20 @@ pj_imoll_o_compute_zone_offset(struct pj_imoll_o_ns::pj_imoll_o_data *Q,
return (xy2.x + Q->pj[zone2 - 1]->x0) - (xy1.x + Q->pj[zone1 - 1]->x0);
}

static double
pj_imoll_o_compute_zone_x_boundary(PJ *P, double lam, double phi) {
PJ_LP lp1, lp2;
PJ_XY xy1, xy2;

lp1.lam = lam - pj_imoll_o_ns::EPSLN;
lp1.phi = phi;
lp2.lam = lam + pj_imoll_o_ns::EPSLN;
lp2.phi = phi;
xy1 = imoll_o_s_forward(lp1, P);
xy2 = imoll_o_s_forward(lp2, P);
return (xy1.x + xy2.x)/2.;
}

PJ *PJ_PROJECTION(imoll_o) {
using namespace pj_imoll_o_ns;

Expand Down Expand Up @@ -273,6 +292,16 @@ PJ *PJ_PROJECTION(imoll_o) {
Q->pj[5]->x0 +=
pj_imoll_o_compute_zone_offset(Q, 6, 3, d90, 0.0 - EPSLN, 0.0 + EPSLN);

/*
The most straightforward way of computing the x locations of the "seams"
in the interrupted projection is to compute the forward transform at the
seams and record these values.
*/
Q->boundary12 = pj_imoll_o_compute_zone_x_boundary(P, -d90, 0.0 + EPSLN);
Q->boundary23 = pj_imoll_o_compute_zone_x_boundary(P, d60, 0.0 + EPSLN);
Q->boundary45 = pj_imoll_o_compute_zone_x_boundary(P, -d60, 0.0 - EPSLN);
Q->boundary56 = pj_imoll_o_compute_zone_x_boundary(P, d90, 0.0 - EPSLN);

P->inv = imoll_o_s_inverse;
P->fwd = imoll_o_s_forward;
P->destructor = pj_imoll_o_destructor;
Expand Down
48 changes: 48 additions & 0 deletions test/gie/builtins.gie
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -2575,6 +2575,30 @@ roundtrip 1
accept -2 -1
expect -1314402.165573241888 -124066.283433859542
roundtrip 1
accept -39.99 0.1
expect -5135117.0707450127 12406.8672748194
roundtrip 1
accept -40.01 0.1
expect -5137140.6776947584 12406.8672748194
roundtrip 1
accept -99.99 -0.1
expect -11169097.7713819221 -12406.8672748194
roundtrip 1
accept -100.01 -0.1
expect -11171118.5438199658 -12406.8672748194
roundtrip 1
accept -19.99 -0.1
expect -3123793.9498816459 -12406.8672748194
roundtrip 1
accept -20.01 -0.1
expect -3125812.8326452221 -12406.8672748194
roundtrip 1
accept 79.99 -0.1
expect 6930815.0545556545 -12406.8672748194
roundtrip 1
accept 80.01 -0.1
expect 6932837.7166681662 -12406.8672748194
roundtrip 1

accept -100.0 22.0
expect -11170107.212763708085 2703699.326638640370
Expand Down Expand Up @@ -2627,6 +2651,30 @@ roundtrip 1
accept -2 -1
expect -1759793.139928588411 -124066.283433859542
roundtrip 1
accept -89.99 0.1
expect -10608821.9887007959 12406.8672748194
roundtrip 1
accept -90.01 0.1
expect -10610845.5956505425 12406.8672748194
roundtrip 1
accept 59.99 0.1
expect 4474097.1799880061 12406.8672748194
roundtrip 1
accept 60.01 0.1
expect 4476121.7317749839 12406.8672748194
roundtrip 1
accept -59.99 -0.1
expect -7591833.0556381932 -12406.8672748194
roundtrip 1
accept -60.01 -0.1
expect -7593856.6625879407 -12406.8672748194
roundtrip 1
accept 89.99 -0.1
expect 7491086.1130506080 -12406.8672748194
roundtrip 1
accept 90.01 -0.1
expect 7493109.7200003546 -12406.8672748194
roundtrip 1

accept -140.0 22.0
expect -15638150.097869191319 2703699.326638640370
Expand Down