1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
|
function testionppp
%
% test RTCA/DO229C bug (A.4.4.10.1 A-22,23)
%
az=0:0.1:360;
figure, axes, hold on, box on, grid on;
pos=[80,0];
for i=1:length(az), posp(i,:)=ionppp(pos,[az(i),0]); end
plot(posp(:,2),posp(:,1),'.');
pos=[-75,170];
for i=1:length(az), posp(i,:)=ionppp(pos,[az(i),0]); end
plot(posp(:,2),posp(:,1),'.');
xlim([-180,180]);
ylim([-90,90]);
% pierce point -----------------------------------------------------------------
function posp=ionppp(pos,azel)
re=6378; hion=350;
pos=pos*pi/180;
azel=azel*pi/180;
rp=re/(re+hion)*cos(azel(2));
ap=pi/2-azel(2)-asin(rp);
posp(1)=asin(sin(pos(1))*cos(ap)+cos(pos(1))*sin(ap)*cos(azel(1)));
%if (pos(1)> 70.0*pi/180& tan(ap)*cos(azel(1))>tan(pi/2-pos(1)))|...
% (pos(1)>-70.0*pi/180&-tan(ap)*cos(azel(1))>tan(pi/2-pos(1))) % DO229C
if (pos(1)> 70.0*pi/180& tan(ap)*cos(azel(1))>tan(pi/2-pos(1)))|...
(pos(1)<-70.0*pi/180&-tan(ap)*cos(azel(1))>tan(pi/2+pos(1))) % corrected
posp(2)=pos(2)+pi-asin(sin(ap)*sin(azel(1))/cos(posp(1)));
else
posp(2)=pos(2)+asin(sin(ap)*sin(azel(1))/cos(posp(1)));
end
posp=posp*180/pi;
if posp(2)>180, posp(2)=posp(2)-360; end
|
