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<?
header ("Content-type: image/gif" );
// Run the elements math and output to a gif file
//
// ------------------------------ Constants --------------------------------------- //
define ("earth_grav_const" , 3.986e5); // Earth's Gravitational Const. (Km^3/s^2)
define ("eg_4pi" , 10096.66709265246); // Earth's Gravitational Const. / 4*pi^2
define ("sideral_day_sec" , 86164.0984); // One Earth Rotation in seconds
define ("equatorial_radius", 6378.137); // WGS-84
define ("flattening" , 298.257223563); // 1/flattening per WGS-84
define ("ghaa_deg" , 99.4033); // The angle between the Greenwich meridian
define ("date_of_GHAA" , "1/1/1990 00:00"); // and 'Aries' at this date in Degrees
define ("Tropical_year" , 365.242197); // Tropical Year in days
define ("c" , 2.99792458e5); // speed of light in Km/s
// The amount the earth rotates during the 3 minutes and 5.59 seconds
// difference between the 24 hrs (Solar) day and the sidereal day
$extra_earth_rot_per_day = (2 * M_PI) / Tropical_year;
// The total earth rotation in one Solar Day = 1 sideral day + the above figure
$earth_rot_rad_sec = ($extra_earth_rot_per_day + (2 * M_PI))/86400; // Earth Rotation Rate (radians/sec)
// The Data from the form is needed earlier since the time array will be inside the main loop
$observer_site = $_GET ['loc_name'];
$observer_lat = $_GET ['loc_lat'];
$observer_long = $_GET ['loc_lon'];
$observer_alt = $_GET ['loc_alt'];
$observer_alt = $observer_alt/1000;
$observer_lat_sign = $_GET ['lat_menu'];
$observer_long_sign = $_GET ['lon_menu'];
if ($observer_lat_sign == South) $observer_lat = -$observer_lat;
if ($observer_long_sign == West ) $observer_long = -$observer_long;
$range_units = $_GET ['range_units'];
$symbol_rate = $_GET ['sym_rate'];
$no_steps = $_GET ['steps'];
$interval = $_GET ['interval'];
$time_unit = $_GET ['time_units'];
$sec_per_step = $interval * $time_unit;
$no_steps = $no_steps + 1; // 2010.03.23 - we're plotting segments, we need n+1 points for n segments
// Observer's UNIT vector In Geocentric Equatorial Coordinates
// These are NOT Inertial coordinates, they are referenced to Greenwich
$obs_lat_rad = deg2rad($observer_lat);
$obs_long_rad = deg2rad($observer_long);
$observer_up_x = cos($obs_lat_rad) * cos($obs_long_rad);
$observer_up_y = cos($obs_lat_rad) * sin($obs_long_rad);
$observer_up_z = sin($obs_lat_rad);
$observer_east_x = -sin($obs_long_rad);
$observer_east_y = cos($obs_long_rad);
$observer_north_x= -sin($obs_lat_rad) * cos($obs_long_rad);
$observer_north_y= -sin($obs_lat_rad) * sin($obs_long_rad);
$observer_north_z= cos($obs_lat_rad);
//Observer's XYZ coordinates on the surface of the earth.
$polar_radius = equatorial_radius * (1 - (1/flattening));
$rx = ( pow(equatorial_radius,2) / sqrt( (pow(equatorial_radius,2) * pow(cos($obs_lat_rad),2) + (pow($polar_radius,2) * pow(sin($obs_lat_rad ),2))))) + $observer_alt;
$rz = ( pow($polar_radius,2) / sqrt( (pow(equatorial_radius,2) * pow(cos($obs_lat_rad),2) + (pow($polar_radius,2) * pow(sin($obs_lat_rad ),2))))) + $observer_alt;
$observer_x = $observer_up_x * $rx;
$observer_y = $observer_up_y * $rx;
$observer_z = $observer_up_z * $rz;
$sat_no = $_GET ['sat_list'];
$slist = $_GET ['list'];
//$sat_no = $sat_no+1;
if ($slist == 1) $tle_data = fopen('geo.txt',"r");
if ($slist == 3) $tle_data = fopen('stations.txt',"r");
if ($slist == 2) $tle_data = fopen('visual.txt' ,"r");
// $tle_data = fopen ('geo.txt',"r"); // 2010.3.22 - Hosting disabled access to off-site files, TLE file now hard coded to 'geo.txt'
if (!tle_data) nofile($tle_url); if (!tle_data) return;
$no_of_sat=0;
while ((!feof ($tle_data)) and ($tle_data))
{
$buffer1a = fgets($tle_data, 128);
$buffer2a = fgets($tle_data, 128);
$buffer3a = fgets($tle_data, 128);
$raw_sat_ele[$no_of_sat] = array ('Name' => $buffer1a,
'line1' => $buffer2a,
'line2' => $buffer3a);
$no_of_sat++;
}
$tle_data = array_sort ($raw_sat_ele, 'Name');
$name = $tle_data[$sat_no]['Name'];
$line1 = $tle_data[$sat_no]['line1'];
$line2 = $tle_data[$sat_no]['line2'];
$sat_name = substr ($name, 0, 24 );
$sat_cata = substr ($line1, 2, 5 );
$sat_launch_year = substr ($line1, 9, 2 );
$sat_launch_no = substr ($line1, 11, 3 );
$sat_payload_no = substr ($line1, 14, 1 );
$epoch_year = substr ($line1, 18, 2 );
$epoch_sider_day = substr ($line1, 20, 3 );
$epoch_sider_time = substr ($line1, 23, 9 );
$sat_inclination = substr ($line2, 8, 8 );
$sat_ra_asc_node = substr ($line2, 17, 8 );
$sat_eccentricity = substr ($line2, 26, 7 );
$sat_arg_perigee = substr ($line2, 34, 8 );
$sat_mean_anomaly = substr ($line2, 43, 8 );
$sat_mean_motion = substr ($line2, 52, 11 );
$sat_rev_at_epoch = substr ($line2, 63, 5 );
// --------------------- resolve for given satellite number of steps -----------//
$max_az = 0; $min_az = 360; // used for calculating min and max
$max_el = 0; $min_el = 90; //for the graph's scale
for ($step=0; $step<$no_steps; $step++) //-------------------------------------- //
{
// Initializing the Current Date Array
$curr_date_array = getdate(time() + ($step * $sec_per_step));
$curr_year = $curr_date_array ['year'];
$curr_day = $curr_date_array ['yday'] + 1; // php counts days from 0, TLE epoch counts from 1
$curr_sec =($curr_date_array ['hours'] * 3600) +
($curr_date_array ['minutes'] * 60) +
$curr_date_array ['seconds']; // - 3600; // Misterious One Hour shift (20.10.03 - 26.10.03) Possible DST bug
$curr_time_unix = $curr_date_array [0];
$curr_frac_day = $curr_sec / 86400; // This is how the sidereal time appears in the TLEs, fraction of solar day
// Bringing the RA in sync with the current time.
// Seconds since reference GHAA was specified
$delta_ghaa_sec = $curr_time_unix - (strtotime (date_of_GHAA)); // time is in seconds since 1.1.70 (UNIX time)
// The current Angle to Aries from the Greenwich meridian. This is the X axis of the Geocentric Inetial coordinates
$current_ghaa_rad = deg2rad(ghaa_deg) + ($delta_ghaa_sec * $earth_rot_rad_sec);
$cos_ghaa = cos(-$current_ghaa_rad);
$sin_ghaa = sin(-$current_ghaa_rad);
// Calculating elapsed time since epoch
$ep_yr = $epoch_year;
if ($ep_yr>60) $ep_yr = $ep_yr + 1900;
if ($ep_yr<60) $ep_yr = $ep_yr + 2000;
$ep_dy = $epoch_sider_day;
$ep_tm = $epoch_sider_time;
$ep_tm_sec = $ep_tm * 86400;
$ep_unix_y = getdate( mktime (0, 0, 0, 1, 1, $ep_yr) ); // Used to calculate time since epoch taking
$ep_unix_s = $ep_unix_y[0] + (($ep_dy + $ep_tm) * 86400); // into account leap years
$delta_sec = $curr_time_unix - $ep_unix_s;
$delta_frac_yr = $delta_sec / (86400 * Tropical_year);
// Calculating Axes of the elliptic orbit
$mean_motion = $sat_mean_motion; // Mean Motion in the TLE is given in Revolution / Day
$period = ( 1 / $mean_motion) * (24 * 60 * 60); // Aug 2017, use period for Solar day
$eccentricity = $sat_eccentricity;
$eccentricity = $eccentricity/1e7; // Eccentricity in the TLEs assumes decimal point
$semi_major_axis = pow((eg_4pi*pow($period, 2)),(1/3));
$semi_minor_axis = $semi_major_axis * sqrt(1-pow($eccentricity,2));
// Find the 'Eccentric Anomaly' by iterating (Newton's Method)
// Mean Anomaly = Ecc Anomaly - (Eccentricity * Sin (Ecc Anomaly))
$mean_mot_rad_sec = ($mean_motion * 2 * M_PI) / 86400; // Mean Motion in RAD / sec
$mean_anomaly_deg = $sat_mean_anomaly; // Mean Anomaly in the TLE is given in Degrees
$mean_anomaly_rad = deg2rad($mean_anomaly_deg);
$rads_since_epoch = ($mean_mot_rad_sec * $delta_sec) + $mean_anomaly_rad; // (Mean Motion * Elapsed time) + Mean Anomaly
$frac_rev = $rads_since_epoch - (2 * M_PI * ( floor( $rads_since_epoch / (2 * M_PI) ) ));
// Do the iterations with this initial value
$ecc_an = $frac_rev;
do
{
$cos_ea = cos ($ecc_an);
$sin_ea = sin ($ecc_an);
$denom = 1 - ($cos_ea * $eccentricity);
$iter = ( $ecc_an - ( $eccentricity * $sin_ea) - $rads_since_epoch ) / $denom;
$ecc_an = $ecc_an - $iter;
} while (abs($iter) > 0.0000025);
$sat_range = $semi_major_axis * $denom; // Satellite range from the CENTER of the earth
// Calculating Satellite position vector on the Orbital Plane
$sat_orb_plane_X = $semi_major_axis * ($cos_ea - $eccentricity);
$sat_orb_plane_Y = $semi_minor_axis * $sin_ea;
// Partial Rotation Matrix to transform from the Orbital Plane to Inertial (Celestial) Coordinates
$incl = $sat_inclination;
$argpg = $sat_arg_perigee;
$raan = $sat_ra_asc_node;
$cos_arg_per = cos (deg2rad($argpg));
$sin_arg_per = sin (deg2rad($argpg));
$cos_raan = cos (deg2rad($raan));
$sin_raan = sin (deg2rad($raan));
$cos_incl = cos (deg2rad($incl));
$sin_incl = sin (deg2rad($incl));
$cel_x_x = ( $cos_arg_per * $cos_raan) - ($sin_arg_per * $sin_raan * $cos_incl); $cel_x_y = (-$sin_arg_per * $cos_raan) - ($cos_arg_per * $sin_raan * $cos_incl);
$cel_y_x = ( $cos_arg_per * $sin_raan) + ($sin_arg_per * $cos_raan * $cos_incl); $cel_y_y = (-$sin_arg_per * $sin_raan) + ($cos_arg_per * $cos_raan * $cos_incl);
$cel_z_x = ( $sin_arg_per * $sin_incl); $cel_z_y = ( $cos_arg_per * $sin_incl);
// Calculatins Satellite position vector in Celestial Coordinates
$sat_celestial_X = ($sat_orb_plane_X * $cel_x_x) + ($sat_orb_plane_Y * $cel_x_y);
$sat_celestial_Y = ($sat_orb_plane_X * $cel_y_x) + ($sat_orb_plane_Y * $cel_y_y);
$sat_celestial_Z = ($sat_orb_plane_X * $cel_z_x) + ($sat_orb_plane_Y * $cel_z_y);
// Satellite Coordinates in Geocentric Equatorial Coordinates (from RA to LONG, etc.)
$sat_geoc_x = ( $sat_celestial_X * $cos_ghaa ) - ( $sat_celestial_Y * $sin_ghaa );
$sat_geoc_y = ( $sat_celestial_X * $sin_ghaa ) + ( $sat_celestial_Y * $cos_ghaa );
$sat_geoc_z = $sat_celestial_Z ;
// Calculate Subsatellite Point
$sub_sat_long = rad2deg(atan2($sat_geoc_y, $sat_geoc_x)); // East / West
$sub_sat_lat = rad2deg(asin ($sat_geoc_z/$sat_range )); // North / South
// Calculating Range Vector
$range_x = $sat_geoc_x - $observer_x;
$range_y = $sat_geoc_y - $observer_y;
$range_z = $sat_geoc_z - $observer_z;
$range_magnitude = sqrt(pow($range_x,2)+pow($range_y,2)+pow($range_z,2));
$range_norm_x = $range_x / $range_magnitude; //Normalized Range Vector
$range_norm_y = $range_y / $range_magnitude;
$range_norm_z = $range_z / $range_magnitude;
$range_up = ($range_norm_x * $observer_up_x) + ($range_norm_y * $observer_up_y) + ($range_norm_z * $observer_up_z);
$range_east = ($range_norm_x * $observer_east_x) + ($range_norm_y * $observer_east_y);
$range_north= ($range_norm_x * $observer_north_x)+ ($range_norm_y * $observer_north_y) + ($range_norm_z * $observer_north_z);
// Calculating the Look Angles
$obs_elevation = rad2deg(asin($range_up));
if ($obs_elevation < 0) {$obs_elevation = 0;}
$obs_azimuth = rad2deg(atan2($range_east,$range_north));
if ( $obs_azimuth < 0 ) $obs_azimuth = 360 + $obs_azimuth;
if ( $obs_azimuth >360) $obs_azimuth = $obs_azimuth % 360;
// Calculating the range according to the units
// if ($range_units == 'Kilometers' ) $range_print = round ($range_magnitude,2);
// if ($range_units == 'milliseconds' ) $range_print = round ((($range_magnitude * 1000) / c) , 2) ;
// if ($range_units == 'symbols' ) $range_print = round ((($range_magnitude * 1000 * $symbol_rate) / c) , 2) ;
// -- Filling an Array with the results --
$results[$step] = array ('Az' => $obs_azimuth,
'El' => $obs_elevation );
if ($obs_azimuth >= $max_az) $max_az = $obs_azimuth;
if ($obs_azimuth < $min_az) $min_az = $obs_azimuth;
if ($obs_elevation >= $max_el) $max_el = $obs_elevation;
if ($obs_elevation < $min_el) $min_el = $obs_elevation;
}
// ----------------------- END of main Loop ------------------------------ //
// ----------------------- Graph the analema ------------------------------ //
$width = 460; $height = $width;
$reduce = 0.85;
$analema = imageCreate($width,$width);
$color_bkg = imageColorAllocate($analema, 0, 0, 0);
$color_plot= imageColorAllocate($analema, 255, 0, 0);
$color_grid= imageColorAllocate($analema, 255,255,255);
$colo2_plot= imageColorAllocate($analema, 0,255, 0);
imageFilledRectangle ($analema, 0, 0, $width-1, $height-1, $color_bkg);
imageLine ($analema , 0 , $height/2, $width , $height/2, $color_grid);
imageLine ($analema , $width/2, 0, $width/2, $height , $color_grid);
imageString ($analema , 5, 3, 3, "Analema for $sat_name", $color_grid);
$lon_pr = abs(round($observer_long,2));
$lat_pr = abs(round($observer_lat, 2));
if ($observer_lat_sign == North) $lat_pr .= " N";
if ($observer_lat_sign == South) $lat_pr .= " S";
if ($observer_long_sign == West) $lon_pr .= " W";
if ($observer_long_sign == East) $lon_pr .= " E";
imageString ($analema , 3, 4, 18, "Observed from $lat_pr $lon_pr", $color_grid);
$per_pr = round ((( $no_steps * $interval * $time_unit ) / 3600),1);
imageString ($analema , 2, 4, 30, "Period: $per_pr hr.", $color_grid);
// imageString ($analema , 2, 8, 40, "Min AZ $min_az Max AZ $max_az", $color_grid);
// imageString ($analema , 2, 8, 50, "Min EL $min_el Max EL $max_el", $color_grid);
$az_origin = round (($min_az + (($max_az - $min_az)/2)),3);
$el_origin = round (($min_el + (($max_el - $min_el)/2)),3);
$x_min = ($results[0]['Az']) - $az_origin;
$x_max = $x_min + 0.01;
$y_min = ($results[0]['El']) - $el_origin;
$y_max = $y_min + 0.01;
for ($step=0; $step<($no_steps); $step++) // First pass to calculate scale
{
$az_step = $results[$step]['Az'];
$el_step = $results[$step]['El'];
$x = ($az_step - $az_origin );
$y = ($el_step - $el_origin );
if ($x > $x_max) $x_max = $x;
if ($x < $x_min) $x_min = $x;
if ($y > $y_max) $y_max = $y;
if ($y < $y_min) $y_min = $y;
$plot[$step] = array ('x' => $x, 'y' => $y );
}
$scale_x = $reduce * ($width / ( $x_max - $x_min )); //pixels per degree
$scale_y = $reduce * ($height / ( $y_max - $y_min ));
// 2010.03.23 - using same scale for both axis
//imageString ($analema , 2, 8, 40, "scale $scale_x $scale_y", $color_grid);
if ($scale_x < $scale_y)
{$scale_y=$scale_x;} else
{$scale_x=$scale_y;}
//imageString ($analema , 2, 8, 50, "scale $scale_x_ratio $scale_y_ratio", $color_grid);
$min_az_pr = round ($az_origin - (($width /2)/$scale_x),2);
$max_el_pr = round ($el_origin + (($height/2)/$scale_y),2);
imageString ($analema , 1, 3, $height - 15, "$min_az_pr", $color_grid);
imageString ($analema , 1, ($width/2)+8, $height - 15, "$az_origin", $color_grid);
imageString ($analema , 1, ($width-36), 3, "$max_el_pr", $color_grid);
imageString ($analema , 1, ($width-36),($height/2)-15, "$el_origin", $color_grid);
for ($step=1; $step<$no_steps; $step++)
{
$x1 = ($width / 2) + ( ($plot[$step]['x']) * $scale_x );
$y1 = ($height / 2) - ( ($plot[$step]['y']) * $scale_y ); // Elevation was being plotted from as mirror, 0 on top
$x0 = ($width / 2) + ( ($plot[$step-1]['x']) * $scale_x );
$y0 = ($height / 2) - ( ($plot[$step-1]['y']) * $scale_y );
//imageString ($analema, 3, 5, 90+($step*12), "x {$plot[$step]['x']} y {$plot[$step]['y']}", $colo2_plot);
if ( abs($x1-$x0) < ($width*0.52) )
{imageLine ($analema, $x0, $y0, $x1, $y1, $colo2_plot);
// imageLine ($analema, $x0, $y0, $x1, $y1, $color_plot);
// $tmp_print=$x1-$x0;
// imageString ($analema, 3, 5, 90+($step*12), "$tmp_print", $color_plot);
}
}
imagefilledellipse ($analema, $x1, $y1, 6, 6, $color_plot);
imageInterlace ($analema , 1);
imageGIF ($analema );
function array_sort($array, $key)
{
for ($i = 0; $i < sizeof($array); $i++)
{ $sort_values[$i] = $array[$i][$key]; }
asort ($sort_values);
reset ($sort_values);
while (list ($arr_key, $arr_val) = each ($sort_values))
{ $sorted_arr[] = $array[$arr_key]; }
return $sorted_arr;
}
function rarray_sort($array, $key)
{
for ($i = 0; $i < sizeof($array); $i++)
{ $sort_values[$i] = $array[$i][$key]; }
arsort ($sort_values);
reset ($sort_values);
while (list ($arr_key, $arr_val) = each ($sort_values))
{ $sorted_arr[] = $array[$arr_key]; }
return $sorted_arr;
}
?>
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