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## Copyright (C) 2014-2022 Michael Hirsch, Ph.D.
## Copyright (C) 2013-2022 Felipe Geremia Nievinski
## Copyright (C) 2020-2022 Philip Nienhuis
##
## Redistribution and use in source and binary forms, with or without
## modification, are permitted provided that the following conditions are met:
## 1. Redistributions of source code must retain the above copyright notice,
## this list of conditions and the following disclaimer.
## 2. Redistributions in binary form must reproduce the above copyright notice,
## this list of conditions and the following disclaimer in the documentation
## and/or other materials provided with the distribution.
## THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
## AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
## THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
## ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
## LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
## CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
## SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
## OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
## WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
## (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
## SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
## -*- texinfo -*-
## @deftypefn {Function File} {@var{n}, @var{e}, @var{d} =} ecef2ned (@var{x}, @var{y}, @var{z}, @var{lat0}, @var{lon0}, @var{alt0})
## @deftypefnx {Function File} {@var{n}, @var{e}, @var{d} =} ecef2ned (@var{x}, @var{y}, @var{z}, @var{lat0}, @var{lon0}, @var{alt0}, @var{spheroid})
## @deftypefnx {Function File} {@var{n}, @var{e}, @var{d} =} ecef2ned (@var{x}, @var{y}, @var{z}, @var{lat0}, @var{lon0}, @var{alt0}, @var{spheroid}, @var{angleUnit})
## Convert Earth Centered Earth Fixed (ECEF) coordinates to local North,
## East, Down (NED) coordinates.
##
## Inputs:
## @itemize
## @item
## @var{x}, @var{y}, @var{z}:
## ECEF coordinates of target points (length units equal to length unit of
## used referenceEllipsoid, of which the default is meters). Can be scalars
## but vectors and nD arrays are accepted if they have equal dimensions.
##
## @item
## @var{lat0}, @var{lon0}, @var{alt0}: latitude, longitude and height of local
## observer point(s). Length unit of local height: see above. In case of
## multiple local locations their numbers and dimensions should match those of
## the target points (i.e., one observer location for each target point).
##
## @item
## (Optional) @var{spheroid}: referenceEllipsoid specified as EPSG number,
## ellipsoid name, or parameter struct. An empty string ("") or empty numeric
## array ([]) is also accepted. Default is WGS84.
##
## @item
## (Optional) @var{angleUnit}: string for angular units ('radians' or
## 'degrees'), only the first letter matters. Default is 'd': degrees.
## @end itemize
##
## Outputs:
## @itemize
## @item
## @var{n}, @var{e}, @var{d}: North, East, Down: local cartesian coordinates
## of target point(s) (default length unit that of invoked referenceEllipsoid,
## of which the default is meters).
## @end itemize
##
## Example:
## @example
## [n, e, d] = ecef2ned (660930, -4701424, 4246579, 42, -82, 200, ...
## "wgs84", "degrees")
## -->
## n = 286.56
## e = 186.12
## d = -939.10
## @end example
##
## @seealso{ned2ecef, ecef2aer, ecef2enu, ecef2enuv, ecef2geodetic, ecef2nedv,
## referenceEllipsoid}
## @end deftypefn
## Function adapted by anonymous contributor, see:
## https://savannah.gnu.org/patch/index.php?9923
function [n, e, d] = ecef2ned (varargin)
spheroid = "";
angleUnit = "degrees";
if (nargin < 6 || nargin > 8)
print_usage();
elseif (nargin == 6)
## Assume ECEF & lat0, lon0, alt0 coordinates given
elseif (nargin == 7)
if (isnumeric (varargin{7}))
## EPSG spheroid code
spheroid = num2str (varargin{7});
elseif (ischar (varargin{7}))
if (! isempty (varargin{7}) && ismember (varargin{7}(1), {"r", "d"}))
angleUnit = varargin{7};
else
spheroid = varargin{7};
endif
elseif (isstruct (varargin{7}))
spheroid = varargin{7};
else
error ("ecef2ned: spheroid or angleUnit expected for arg. #7");
endif
elseif (nargin == 8)
spheroid = varargin{7};
angleUnit = varargin{8};
endif
x = varargin{1};
y = varargin{2};
z = varargin{3};
lat0 = varargin{4};
lon0 = varargin{5};
alt0 = varargin{6};
if (! isnumeric (x) || ! isreal (x) || ...
! isnumeric (y) || ! isreal (y) || ...
! isnumeric (z) || ! isreal (z) || ...
! isnumeric (lat0) || ! isreal (lat0) || ...
! isnumeric (lon0) || ! isreal (lon0) || ...
! isnumeric (alt0) || ! isreal (alt0))
error ("ecef2ned : numeric real input expected for first 6 input args.");
endif
if (! all (size (x) == size (y)) || ! all (size (y) == size (z)))
error ("ecef2ned: non-matching dimensions of ECEF inputs.");
endif
if (! (isscalar (lat0) && isscalar (lon0) && isscalar (alt0)))
## Check if for each test point a matching observer point is given
if (! all (size (lat0) == size (x)) || ...
! all (size (lon0) == size (y)) || ...
! all (size (alt0) == size (z)))
error (["ecef2ned: non-matching dimensions of observer points and ", ...
"target points"]);
endif
endif
E = sph_chk (spheroid);
if (! ischar (angleUnit) || ! ismember (lower (angleUnit(1)), {"d", "r"}))
error ("ecef2ned: angleUnit should be one of 'degrees' or 'radians'")
endif
[x0, y0, z0] = geodetic2ecef (E, lat0, lon0, alt0, angleUnit);
[n, e, d] = ecef2nedv (x - x0, y - y0, z - z0, lat0, lon0, angleUnit);
endfunction
%!test
%! [n, e, d] = ecef2ned (660930.192761082, -4701424.222957011, 4246579.604632881, 42, -82, 200);
%! assert([n, e, d], [286.84222, 186.27752, -939.69262], 10e-6);
%!test
%! Rad = deg2rad ([42, -82]);
%! [e, n, u] = ecef2ned (660930.192761082, -4701424.222957011, 4246579.604632881, Rad(1), Rad(2), 200, "rad");
%! assert ([e, n, u], [286.84, 186.28, -939.69], 10e-3);
%!test
%! [a, b, c] = ecef2ned (5507528.9, 4556224.1, 6012820.8, 45.9132, 36.7484, 1877753.2);
%! assert ([a, b, c], [-923083.1558, 355601.2616, -1041016.4238], 1e-4);
%!test
%! [nn, ee, dd] = ecef2ned (1345660, -4350891, 4452314, 44.532, -72.782, 1699);
%! assert ([nn, ee, dd], [1334.3045, -2544.3677, 359.9609], 1e-4);
%!error <angleUnit> ecef2ned (45, 45, 100, 50, 50, 200, "", "km")
%!error <numeric real input expected> ecef2ned ("A", 45, 100, 50, 50, 200)
%!error <numeric real input expected> ecef2ned (45i, 45, 100, 50, 50, 200)
%!error <numeric real input expected> ecef2ned (45, "A", 100, 50, 50, 200)
%!error <numeric real input expected> ecef2ned (45, 45i, 100, 50, 50, 200)
%!error <numeric real input expected> ecef2ned (45, 45, "A", 50, 50, 200)
%!error <numeric real input expected> ecef2ned (45, 45, 100i, 50, 50, 200)
%!error <numeric real input expected> ecef2ned (45, 45, 100, "A", 50, 200)
%!error <numeric real input expected> ecef2ned (45, 45, 100, 50i, 50, 200)
%!error <numeric real input expected> ecef2ned (45, 45, 100, 50, "A", 200)
%!error <numeric real input expected> ecef2ned (45, 45, 100, 50, 50i, 200)
%!error <numeric real input expected> ecef2ned (45, 45, 100, 50, 50, "A")
%!error <numeric real input expected> ecef2ned (45, 45, 100, 50, 50, 200i)
%!error <non-matching> ecef2ned ([1 1], [2 2]', [3 3], 4, 5, 6)
%!error <non-matching> ecef2ned ([1 1], [2 2], [33], 4, 5, 6)
%!error <non-matching> ecef2ned ([1 1], [2 2], [3 3], [4 4], 5, 6)
%!error <non-matching> ecef2ned ([1 1], [2 2], [3 3], 4, [5 5], 6)
%!error <non-matching> ecef2ned ([1 1], [2 2], [3 3], [4; 4], [5; 5], [6; 6])
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