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Do all the numerical work for surface fitting around 0,0,0 to reduce problems

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with floating point roundoff.
This commit is contained in:
curt 2005-09-09 20:47:04 +00:00
parent 3b879d29c2
commit d4ffe52562
2 changed files with 34 additions and 41 deletions
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71
src/Airports/GenAirports/apt_surface.cxx
View file

@ -205,7 +205,7 @@ TGAptSurface::TGAptSurface( const string& path,
SG_LOG( SG_GENERAL, SG_DEBUG, " val_ave = " << val_ave );
Pts->set(i, j, Point3D( min_deg.lon() + i * dlon,
min_deg.lat() + j * dlat,
val_ave )
val_ave )
);
SG_LOG( SG_GENERAL, SG_DEBUG, "lon_ave = " << lon_ave
<< " lat_ave = " << lat_ave );
@ -254,29 +254,16 @@ TGAptSurface::TGAptSurface( const string& path,
}
#endif
// compute an central offset point.
double clon = (min_deg.lon() + max_deg.lon()) / 2.0;
double clat = (min_deg.lat() + max_deg.lat()) / 2.0;
offset = Point3D( clon, clat, average_elev_m );
cout << "Central offset point = " << offset << endl;
// Create the fitted surface
SG_LOG(SG_GENERAL, SG_DEBUG, "ready to create fitted surface");
fit();
// sanity check: I'm finding that leastSquares() can produce nan
// surfaces. We test for this and fall back to globalInterp() if
// the least squares fails.
double result = query( (min_deg.lon() + max_deg.lon()) / 2.0,
(min_deg.lat() + max_deg.lat()) / 2.0 );
if ( result > -9000.0 ) {
// ok, a valid number
} else {
SG_LOG(SG_GENERAL, SG_WARN,
"leastSquares() fit seemed to fail!!!");
char command[256];
sprintf( command,
"echo least squares nurbs interpolation failed, using globalInterp() >> last_apt" );
system( command );
// abort and force developer to debug for now
exit(-1);
}
SG_LOG(SG_GENERAL, SG_DEBUG, " successful.");
SG_LOG(SG_GENERAL, SG_DEBUG, " fit process successful.");
#ifdef DEBUG
// For debugging only: output an array of surface points suitable
@ -307,8 +294,8 @@ TGAptSurface::~TGAptSurface() {
static ColumnVector qr_method( Real* y,
Real* t1, Real* t2, Real* t3, Real* t4,
Real* t5, Real* t6, Real* t7, Real* t8,
/* Real* t9, Real* t10, Real* t11, Real* t12,
Real* t13, Real* t14, Real* t15, */
Real* t9, Real* t10, Real* t11, Real* t12,
Real* t13, Real* t14, Real* t15,
int nobs, int npred )
{
cout << "QR triangularisation" << endl;;
@ -329,13 +316,13 @@ static ColumnVector qr_method( Real* y,
X.column(7) << t6;
X.column(8) << t7;
X.column(9) << t8;
/* X.column(10) << t9;
X.column(10) << t9;
X.column(11) << t10;
X.column(12) << t11;
X.column(13) << t12;
X.column(14) << t13;
X.column(15) << t14;
X.column(16) << t15; */
X.column(16) << t15;
Y << y;
// do Householder triangularisation
@ -382,9 +369,9 @@ void TGAptSurface::fit() {
// A13*y*y*y + A14*x*y*y*y + A15*x*x*y*y*y
int nobs = Pts->cols() * Pts->rows(); // number of observations
int npred = 8; // number of predictor values A[n]
int npred = 15; // number of predictor values A[n]
Real z[nobs];
Real tz[nobs];
Real t1[nobs];
Real t2[nobs];
Real t3[nobs];
@ -393,23 +380,24 @@ void TGAptSurface::fit() {
Real t6[nobs];
Real t7[nobs];
Real t8[nobs];
/* Real t9[nobs];
Real t9[nobs];
Real t10[nobs];
Real t11[nobs];
Real t12[nobs];
Real t13[nobs];
Real t14[nobs];
Real t15[nobs]; */
Real t15[nobs];
// generate the required fit data
for ( int j = 0; j < Pts->rows(); j++ ) {
for ( int i = 0; i < Pts->cols(); i++ ) {
Point3D p = Pts->element( i, j );
int index = ( j * Pts->cols() ) + i;
Real x = p.x();
Real y = p.y();
cout << "pt = " << x << "," << y << "," << p.z() << endl;
z[index] = p.z();
Real x = p.x() - offset.x();
Real y = p.y() - offset.y();
Real z = p.z() - offset.z();
cout << "pt = " << x << "," << y << "," << z << endl;
tz[index] = z;
t1[index] = x;
t2[index] = x*y;
t3[index] = y;
@ -418,13 +406,13 @@ void TGAptSurface::fit() {
t6[index] = x*x*y*y;
t7[index] = y*y;
t8[index] = x*y*y;
/* t9[index] = x*x*x;
t9[index] = x*x*x;
t10[index] = x*x*x*y;
t11[index] = x*x*x*y*y;
t12[index] = x*x*x*y*y*y;
t13[index] = y*y*y;
t14[index] = x*y*y*y;
t15[index] = x*x*y*y*y; */
t15[index] = x*x*y*y*y;
}
}
@ -433,9 +421,9 @@ void TGAptSurface::fit() {
Try {
surface_coefficients
= qr_method( z,
= qr_method( tz,
t1, t2, t3, t4, t5, t6, t7, t8,
/* t9, t10, t11, t12, t13, t14, t15, */
t9, t10, t11, t12, t13, t14, t15,
nobs, npred
);
cout << "surface_coefficients size = " << surface_coefficients.nrows() << endl;
@ -464,14 +452,15 @@ double TGAptSurface::query( double lon_deg, double lat_deg ) {
// A9*x*x*x + A10*x*x*x*y + A11*x*x*x*y*y + A12*x*x*x*y*y*y +
// A13*y*y*y + A14*x*y*y*y + A15*x*x*y*y*y
double x = lon_deg;
double y = lat_deg;
double x = lon_deg - offset.x();
double y = lat_deg - offset.y();
ColumnVector A = surface_coefficients;
double result = A(1) + A(2)*x + A(3)*x*y + A(4)*y + A(5)*x*x + A(6)*x*x*y
+ A(7)*x*x*y*y + A(8)*y*y + A(9)*x*y*y /* + A(10)*x*x*x + A(11)*x*x*x*y
+ A(7)*x*x*y*y + A(8)*y*y + A(9)*x*y*y + A(10)*x*x*x + A(11)*x*x*x*y
+ A(12)*x*x*x*y*y + A(13)*x*x*x*y*y*y + A(14)*y*y*y + A(15)*x*y*y*y
+ A(16)*x*x*y*y*y */;
+ A(16)*x*x*y*y*y;
result += offset.z();
printf("result = %.2f\n", result);

4
src/Airports/GenAirports/apt_surface.hxx
View file

@ -115,9 +115,13 @@ private:
Point3D min_deg, max_deg;
// A central point in the airport area
Point3D offset;
// externally seeded average airport elevation
double average_elev_m;
public:
// Constructor, specify min and max coordinates of desired area in