def approximate_rpc_as_projective(rpc_model,
col_range,
lin_range,
alt_range,
verbose=False):
"""
Returns a least-square approximation of the RPC functions as a projection
matrix. The approximation is optimized on a sampling of the 3D region
defined by the altitudes in alt_range and the image tile defined by
col_range and lin_range.
"""
### step 1: generate cartesian coordinates of 3d points used to fit the
### best projection matrix
# get mesh points and convert them to geodetic then to geocentric
# coordinates
cols, lins, alts = generate_point_mesh(col_range, lin_range, alt_range)
lons, lats, alts = rpc_model.direct_estimate(cols, lins, alts)
x, y, z = geographiclib.geodetic_to_geocentric(lats, lons, alts)
### step 2: estimate the camera projection matrix from corresponding
# 3-space and image entities
world_points = np.vstack([x, y, z]).T
image_points = np.vstack([cols, lins]).T
P = estimation.camera_matrix(world_points, image_points)
### step 3: for debug, test the approximation error
if verbose:
# compute the projection error made by the computed matrix P, on the
# used learning points
colPROJ = np.zeros(len(x))
linPROJ = np.zeros(len(x))
for i in xrange(len(x)):
v = np.dot(P, [[x[i]], [y[i]], [z[i]], [1]])
colPROJ[i] = v[0] / v[2]
linPROJ[i] = v[1] / v[2]
print 'approximate_rpc_as_projective: (min, max, mean)'
print_distance_between_vectors(cols, colPROJ, 'cols')
print_distance_between_vectors(lins, linPROJ, 'rows')
return P
def inverse_estimate(self, lon, lat, alt):
"""
computes the projection location (col, lin) of the 3D point
(lon,lat,alt), on the image. For symmetry, this function returns a
triplet (col, lin, alt). The value of alt is just a copy of the one
given in input.
"""
# convert the geodetic coordinates (lat, lon, alt) to cartesian (x, y, z)
# WARNING: the convention used by CartConvert is (lat, lon, alt), while
# we use (lon, lat, alt)
x, y, z = geographiclib.geodetic_to_geocentric(lat, lon, alt)
# project the 3D point, represented as homogeneous cartesian coordinates
p0 = self.P[0, :]
p1 = self.P[1, :]
p2 = self.P[2, :]
col = p0[0] * x + p0[1] * y + p0[2] * z + p0[3];
lin = p1[0] * x + p1[1] * y + p1[2] * z + p1[3];
n = p2[0] * x + p2[1] * y + p2[2] * z + p2[3];
# homogeneous normalization
return col/n, lin/n, alt
def world_to_image_correspondences_from_rpc(rpc, x, y, w, h, n):
"""
Uses RPC functions to generate a set of world to image correspondences.
Args:
rpc: an instance of the rpc_model.RPCModel class
x, y, w, h: four integers defining a rectangular region of interest
(ROI) in the image. (x, y) is the top-left corner, and (w, h)
are the dimensions of the rectangle. The correspondences
will be located in that ROI.
n: cube root of the desired number of correspondences.
Returns:
an array of correspondences, one per line, expressed as X, Y, Z, x, y.
"""
m, M = altitude_range(rpc, x, y, w, h, 100, -100)
lon, lat, alt = ground_control_points(rpc, x, y, w, h, m, M, n)
x, y, h = rpc.inverse_estimate(lon, lat, alt)
X, Y, Z = geographiclib.geodetic_to_geocentric(lat, lon, alt)
return np.vstack([X, Y, Z]).T, np.vstack([x, y]).T
def inverse_estimate(self, lon, lat, alt):
"""
computes the projection location (col, lin) of the 3D point
(lon,lat,alt), on the image. For symmetry, this function returns a
triplet (col, lin, alt). The value of alt is just a copy of the one
given in input.
"""
# convert the geodetic coordinates (lat, lon, alt) to cartesian (x, y, z)
# WARNING: the convention used by CartConvert is (lat, lon, alt), while
# we use (lon, lat, alt)
x, y, z = geographiclib.geodetic_to_geocentric(lat, lon, alt)
# project the 3D point, represented as homogeneous cartesian coordinates
p0 = self.P[0, :]
p1 = self.P[1, :]
p2 = self.P[2, :]
col = p0[0] * x + p0[1] * y + p0[2] * z + p0[3]
lin = p1[0] * x + p1[1] * y + p1[2] * z + p1[3]
n = p2[0] * x + p2[1] * y + p2[2] * z + p2[3]
# homogeneous normalization
return col / n, lin / n, alt
def approximate_rpc_as_projective(rpc_model, col_range, lin_range, alt_range,
verbose=False):
"""
Returns a least-square approximation of the RPC functions as a projection
matrix. The approximation is optimized on a sampling of the 3D region
defined by the altitudes in alt_range and the image tile defined by
col_range and lin_range.
"""
### step 1: generate cartesian coordinates of 3d points used to fit the
### best projection matrix
# get mesh points and convert them to geodetic then to geocentric
# coordinates
cols, lins, alts = generate_point_mesh(col_range, lin_range, alt_range)
lons, lats, alts = rpc_model.direct_estimate(cols, lins, alts)
x, y, z = geographiclib.geodetic_to_geocentric(lats, lons, alts)
### step 2: estimate the camera projection matrix from corresponding
# 3-space and image entities
world_points = np.vstack([x, y, z]).T
image_points = np.vstack([cols, lins]).T
P = estimation.camera_matrix(world_points, image_points)
### step 3: for debug, test the approximation error
if verbose:
# compute the projection error made by the computed matrix P, on the
# used learning points
colPROJ = np.zeros(len(x))
linPROJ = np.zeros(len(x))
for i in xrange(len(x)):
v = np.dot(P, [[x[i]],[y[i]],[z[i]],[1]])
colPROJ[i] = v[0]/v[2]
linPROJ[i] = v[1]/v[2]
print 'approximate_rpc_as_projective: (min, max, mean)'
print_distance_between_vectors(cols, colPROJ, 'cols')
print_distance_between_vectors(lins, linPROJ, 'rows')
return P
