function [xyz_igp, igp_en_hat, igp_corner_den, igp_mag_lat, inv_igp_mask] =...         init_igps(igp_mask)%*************************************************************************%*     Copyright c 2001 The board of trustees of the Leland Stanford     *%*                      Junior University. All rights reserved.          *%*     This script file may be distributed and used freely, provided     *%*     this copyright notice is always kept with it.                     *%*                                                                       *%*     Questions and comments should be directed to Todd Walter at:      *%*     twalter@stanford.edu                                              *%*************************************************************************%global CONST_H_IONO;%convert to radiansigp_mask_rad=igp_mask*pi/180;%compute the ECEF XYZ positions of the IGPsxyz_igp=llh2xyz(igp_mask_rad(:,1),igp_mask_rad(:,2), CONST_H_IONO);%calculate east and north unit vectors for each IGPcos_lat=cos(igp_mask_rad(:,1));sin_lat=sin(igp_mask_rad(:,1));cos_lon=cos(igp_mask_rad(:,2));sin_lon=sin(igp_mask_rad(:,2));igp_en_hat(:,6)=cos_lat;igp_en_hat(:,5)=-sin_lat.*sin_lon;igp_en_hat(:,4)=-sin_lat.*cos_lon;igp_en_hat(:,3)=0*igp_en_hat(:,4);igp_en_hat(:,2)=cos_lon;igp_en_hat(:,1)=-sin_lon;%calculate lat and lon for cell centers surrounding grid%TODO make this dynamic from the mask rahter than hardcoded for WAASll_give=([igp_mask(:,1)+2.5 igp_mask(:,2)+2.5 ...          igp_mask(:,1)+2.5 igp_mask(:,2)-2.5 ...          igp_mask(:,1)-2.5 igp_mask(:,2)+2.5 ...          igp_mask(:,1)-2.5 igp_mask(:,2)-2.5])*pi/180;%adjust IGPs at or above 55 degrees for larger cellsidx=find(igp_mask(:,1)==55);ll_give(idx,:)=([igp_mask(idx,1)+5.0 igp_mask(idx,2)+5.0 ...                 igp_mask(idx,1)+5.0 igp_mask(idx,2)-5.0 ...                 igp_mask(idx,1)-2.5 igp_mask(idx,2)+2.5 ...                 igp_mask(idx,1)-2.5 igp_mask(idx,2)-2.5])*pi/180;idx=find(igp_mask(:,1)>55);ll_give(idx,:)=([igp_mask(idx,1)+5.0 igp_mask(idx,2)+5.0 ...                 igp_mask(idx,1)+5.0 igp_mask(idx,2)-5.0 ...                 igp_mask(idx,1)-5.0 igp_mask(idx,2)+5.0 ...                 igp_mask(idx,1)-5.0 igp_mask(idx,2)-5.0])*pi/180;xyz_give=[llh2xyz(ll_give(:,1),ll_give(:,2),CONST_H_IONO) ...          llh2xyz(ll_give(:,3),ll_give(:,4),CONST_H_IONO) ...          llh2xyz(ll_give(:,5),ll_give(:,6),CONST_H_IONO) ...          llh2xyz(ll_give(:,7),ll_give(:,8),CONST_H_IONO)];del_xyz=xyz_give-[xyz_igp xyz_igp xyz_igp xyz_igp];[n_igp temp]=size(igp_mask);igp_corner_den=ones(4,3,n_igp);igp_corner_den(1,2,:)=sum((del_xyz(:,1:3).*igp_en_hat(:,1:3))')'*1e-6;igp_corner_den(1,3,:)=sum((del_xyz(:,1:3).*igp_en_hat(:,4:6))')'*1e-6;igp_corner_den(2,2,:)=sum((del_xyz(:,4:6).*igp_en_hat(:,1:3))')'*1e-6;igp_corner_den(2,3,:)=sum((del_xyz(:,4:6).*igp_en_hat(:,4:6))')'*1e-6;igp_corner_den(3,2,:)=sum((del_xyz(:,7:9).*igp_en_hat(:,1:3))')'*1e-6;igp_corner_den(3,3,:)=sum((del_xyz(:,7:9).*igp_en_hat(:,4:6))')'*1e-6;igp_corner_den(4,2,:)=sum((del_xyz(:,10:12).*igp_en_hat(:,1:3))')'*1e-6;igp_corner_den(4,3,:)=sum((del_xyz(:,10:12).*igp_en_hat(:,4:6))')'*1e-6;%find the magnetic latitude (see ICD-200)igp_mag_lat=igp_mask(:,1) + 0.064*180*cos(igp_mask_rad(:,2)-1.617*pi);%find the inverse IGP maskinv_igp_mask=find_inv_IGPmask(igp_mask);