/**
* Return mpp for the given coords, coord mode and image size.
*/
static void georef_layer_mpp_from_coords ( VikCoordMode mode, struct LatLon ll_tl, struct LatLon ll_br, guint width, guint height, gdouble *xmpp, gdouble *ympp )
{
struct LatLon ll_tr;
ll_tr.lat = ll_tl.lat;
ll_tr.lon = ll_br.lon;
struct LatLon ll_bl;
ll_bl.lat = ll_br.lat;
ll_bl.lon = ll_tl.lon;
// UTM mode should be exact MPP
gdouble factor = 1.0;
if ( mode == VIK_COORD_LATLON ) {
// NB the 1.193 - is at the Equator.
// http://wiki.openstreetmap.org/wiki/Zoom_levels
// Convert from actual image MPP to Viking 'pixelfact'
gdouble mid_lat = (ll_bl.lat + ll_tr.lat ) / 2.0;
// Protect against div by zero (but shouldn't have 90 degrees for mid latitude...)
if ( fabs(mid_lat) < 89.9 )
factor = cos(DEG2RAD(mid_lat)) * 1.193;
}
gdouble diffx = a_coords_latlon_diff ( &ll_tl, &ll_tr );
*xmpp = (diffx / width) / factor;
gdouble diffy = a_coords_latlon_diff ( &ll_tl, &ll_bl );
*ympp = (diffy / height) / factor;
}
static gdouble vik_coord_diff_safe(const VikCoord *c1, const VikCoord *c2)
{
struct LatLon a, b;
vik_coord_to_latlon ( c1, &a );
vik_coord_to_latlon ( c2, &b );
return a_coords_latlon_diff ( &a, &b );
}
gdouble vik_coord_diff(const VikCoord *c1, const VikCoord *c2)
{
if ( c1->mode == c2->mode )
return vik_coord_diff_safe ( c1, c2 );
if ( c1->mode == VIK_COORD_UTM )
return a_coords_utm_diff ( (const struct UTM *) c1, (const struct UTM *) c2 );
else
return a_coords_latlon_diff ( (const struct LatLon *) c1, (const struct LatLon *) c2 );
}
double a_coords_utm_diff( const struct UTM *utm1, const struct UTM *utm2 )
{
static struct LatLon tmp1, tmp2;
if ( utm1->zone == utm2->zone ) {
return sqrt ( pow ( utm1->easting - utm2->easting, 2 ) + pow ( utm1->northing - utm2->northing, 2 ) );
} else {
a_coords_utm_to_latlon ( utm1, &tmp1 );
a_coords_utm_to_latlon ( utm2, &tmp2 );
return a_coords_latlon_diff ( &tmp1, &tmp2 );
}
}
static gboolean dem_get_ref_points_elev_dist(VikDEM *dem,
gdouble east, gdouble north, /* in seconds */
gint16 *elevs, gint16 *dists)
{
int i;
int cols[4], rows[4];
struct LatLon ll[4];
struct LatLon pos;
if ( east > dem->max_east || east < dem->min_east ||
north > dem->max_north || north < dem->min_north )
return FALSE; /* got nothing */
pos.lon = east/3600;
pos.lat = north/3600;
/* order of the data: sw, nw, ne, se */
/* sw */
cols[0] = (gint) floor((east - dem->min_east) / dem->east_scale);
rows[0] = (gint) floor((north - dem->min_north) / dem->north_scale);
ll[0].lon = (dem->min_east + dem->east_scale*cols[0])/3600;
ll[0].lat = (dem->min_north + dem->north_scale*rows[0])/3600;
/* nw */
cols[1] = cols[0];
rows[1] = rows[0] + 1;
ll[1].lon = ll[0].lon;
ll[1].lat = ll[0].lat + (gdouble)dem->north_scale/3600;
/* ne */
cols[2] = cols[0] + 1;
rows[2] = rows[0] + 1;
ll[2].lon = ll[0].lon + (gdouble)dem->east_scale/3600;
ll[2].lat = ll[0].lat + (gdouble)dem->north_scale/3600;
/* se */
cols[3] = cols[0] + 1;
rows[3] = rows[0];
ll[3].lon = ll[0].lon + (gdouble)dem->east_scale/3600;
ll[3].lat = ll[0].lat;
for (i = 0; i < 4; i++) {
if ((elevs[i] = vik_dem_get_xy(dem, cols[i], rows[i])) == VIK_DEM_INVALID_ELEVATION)
return FALSE;
dists[i] = a_coords_latlon_diff(&pos, &ll[i]);
}
#if 0 /* debug */
for (i = 0; i < 4; i++)
fprintf(stderr, "%f:%f:%d:%d ", ll[i].lat, ll[i].lon, dists[i], elevs[i]);
fprintf(stderr, " north_scale=%f\n", dem->north_scale);
#endif
return TRUE; /* all OK */
}
