Name

CL_gm_pixelSize — Deformation ratio of a pixel for a given altitude and a given swath (tilt)

Calling Sequence

   [K1,K2]=CL_gm_pixelSize(sat_alt,tilt,target_alt,[er])
   
   

Description

  • Computes the deformation ratio K1 (tilt direction) and K2 (direction perpendicular to tilt) of a pixel for a given altitude and a given swath (tilt).

    Deformation ratio is defined as follows :

    Note : this function assumes a spherical earth

  • Last update : 09/11/2009

Parameters

sat_alt:

satellite altitude [m] (1xN)

tilt:

swath or tilt (depointing) angle [rad] (1xN)

target_alt:

(optional) target altitude [m] (default is 0 m)(1xN)

er :

(optional) planet radius (default is earth equatorial radius %CL_eqRad) [m]

K1:

pixel ratio in tilt direction(1xN)

K2:

pixel ratio in perpendicular direction to tilt(1xN)

Authors

CNES - DCT/SB

See also

CL_gm_visiParams

Bibliography

Satellites Orbites et Missions (M Capderou)

Examples

// Example 1
sat_alt = 700.e3;
tilt = CL_deg2rad(20);
[K1,K2]=CL_gm_pixelSize(sat_alt,tilt)
// same computation, with CL_gm_visiParams :
sat_radius = %CL_eqRad + sat_alt;
target_radius = %CL_eqRad;
[dist] = CL_gm_visiParams(sat_radius,target_radius,'sat',tilt,'dist') // distance for the given tilt
[elev] = CL_gm_visiParams(sat_radius,target_radius,'sat',tilt,'elev') // elevation for the given tilt
K1 = dist/(sat_alt * sin(elev))
K2 = dist/sat_alt

// Example 2
tab_f=[];
K1=[];
K2=[];
fground=[];
leg=[];
i=0;
f = scf();
drawlater();
xset("colormap",jetcolormap(10));

for sat_alt=[200000:200000:1400000];
i=i+1;
fground=[fground ,i];
leg=[leg,sat_alt/1000];
f=[0:1:50]*%CL_deg2rad;
[K1,K2]=CL_gm_pixelSize(sat_alt,f)  ;
tab_f=[tab_f;f];
plot(f*%CL_rad2deg,abs(K1))
p=gce();
p.children.foreground=i;
end
a=gca();
a.title.text="DEFORMATION DES PIXELS (K1)";
a.title.foreground = 12;
a.title.font_size = 4;
a.x_label.text="alpha (deg)";
a.x_label.font_size = 4;
a.x_label.foreground = 12;
a.x_location = "bottom";
a.y_label.text=" K1";
a.y_label.font_size = 4;
a.y_label.foreground = 12;
a.y_location = "left";
a.foreground = 12;
a.data_bounds = [0,1;50,6];
legends("sat_alt: "+string(leg)+" km",fground,2);
xgrid();
drawnow();