%                              vecefllw.m
%  Scope:   This MATLAB macro performs the transformation from ECEF frame to 
%           wander azimuth local level frame for a given position vector and 
%           reference latitude/longitude/wander azimuth angles. 
%  Usage:   pllw = vecefllw(pecef,lat,lon,waz)
%  Description of parameters:
%           pecef -  input, ECEF position vector (with components in meters)
%           lat   -  input, reference latitude in radians
%           lon   -  input, reference longitude in radians
%           waz   -  input, reference wander azimuth angle in radians
%           pllw  -  output, local level wander azimuth position vector, with 
%                    components in same units as the input ECEF position vector
%  Remark:  The coordinate axes for wander azimuth local level frame are 
%           defined as follows:
%           x - axis at wander azimuth angle counter-clockwise from East in
%               local level plane,
%           y - axis at wander azimuth angle counter-clockwise from North in
%               local level plane,
%           z - axis upward along local normal
%  Last update:  04/04/00
%  Copyright (C) 1996-00 by LL Consulting. All Rights Reserved.

function   pllw = vecefllw(pecef,lat,lon,waz)

slat = sin(lat);
clat = cos(lat);
slon = sin(lon);
clon = cos(lon);
swaz = sin(waz);
cwaz = cos(waz);

temp1 = clon * pecef(1) + slon * pecef(2);
temp2 = slon * pecef(1) - clon * pecef(2);
temp3 = - slat * temp1 + clat * pecef(3);

pllw = zeros(3,1);
pllw(1) = swaz * temp3 - cwaz * temp2;
pllw(2) = swaz * temp2 + cwaz * temp3;
pllw(3) = clat * temp1 + slat * pecef(3);