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// KEA
// The two main functions use global variables, so we have to
// set all this up unless the functions are going to get changed.
var ClientRecieveTime=new Date();
var QueryTimeZone = -7;
var QueryTimeZoneOffsetMin = QueryTimeZone * 60 // -420
var NISTSendTimeGMTms = ClientRecieveTime.getTime() - ( QueryTimeZoneOffsetMin * 60 * 1000 );
// NIST start time in the query time zone
var QueryTimeZoneOffset = ( QueryTimeZoneOffsetMin * 60 * 1000 ) ;
// Client start time in some time zone
var ClientRecieveTimems = ClientRecieveTime.getTime() ;
// what timezone does your computer think it is? - in minutes
//var ClientTimeZone = Math.floor(NISTSendTime.getTimezoneOffset()) ;
var ClientTimeZone = QueryTimeZoneOffsetMin;
var ClientNISTDelta = Math.floor(NISTSendTimeGMTms - ClientRecieveTimems);
//WScript.echo(QueryTimeZoneOffset)
//WScript.echo(" ")
//WScript.echo(ClientRecieveTime)
//WScript.echo(" ")
//WScript.echo(ClientTimeZone)
//WScript.echo(" ")
//WScript.echo(ClientNISTDelta)
//WScript.echo(" ")
WScript.echo(updatexearthImage());
function updatexearthImage() {
// get the computer's date
var Thisdate = new Date();
// convert to NIST date, using offset calculated in ClientNISTDelta
ThisMilliseconds = Thisdate.getTime() + ClientNISTDelta ;
// KEA get rid of reference to DOM, just return the data
// document.images['xearth'].src = xearthSrc(ThisMilliseconds);
return xearthSrc(ThisMilliseconds);
// setTimeout("updatexearthImage()", 10000);
}
function xearthSrc(ThisMilliseconds) {
var ssue = ThisMilliseconds / 1000;
var TWOPI = 2 * Math.PI;
var EpochStart = 631065600;
var DaysSinceEpoch = (ssue - EpochStart) / (24*3600);
var RadsPerDay = TWOPI / 365.242191;
var Epsilon_g = 279.403303 * (TWOPI / 360);
var OmegaBar_g = 282.768422 * (TWOPI / 360);
var Eccentricity = 0.016713;
var MeanObliquity = 23.440592 * (TWOPI / 360);
//Compute lambda = sun_ecliptic_longitude(ssue)
//Begin sun_ecliptic_longitude
var D = DaysSinceEpoch;
var N = RadsPerDay * D;
N = N % TWOPI;
if (N < 0) N += TWOPI;
var M_sun = N + Epsilon_g - OmegaBar_g;
if (M_sun < 0) M_sun += TWOPI;
//Compute var E = solve_keplers_equation(M_sun);
//Begin solve_keplers_equation
var E = M_sun;
var delta;
while (1) {
delta = E - (Eccentricity*Math.sin(E)) - M_sun;
if (Math.abs(delta) <= 1E-10) break;
E -= delta / (1 - (Eccentricity*Math.cos(E)));
}
//End solve_keplers_equation
var lambda = OmegaBar_g + (2 * Math.atan(Math.sqrt((1+Eccentricity) / (1-Eccentricity)) * Math.tan(E/2)));
//End sun_ecliptic_longitude
//Compute ecliptic_to_equatorial(lambda, 0.0, alpha, delta)
var sin_e = Math.sin(MeanObliquity);
var cos_e = Math.cos(MeanObliquity);
var alpha = Math.atan2(Math.sin(lambda)*cos_e, Math.cos(lambda));
var delta = Math.asin(sin_e*Math.sin(lambda));
//End ecliptic_to_equatorial
//Compute GST(ssue)
//Compute JD = julian_date(year, month, day)
var TmpDate = new Date(ThisMilliseconds);
var OffsetMilliseconds = ThisMilliseconds ; //+ (60000*TmpDate.getTimezoneOffset());
var ThisDate = new Date(OffsetMilliseconds);
var y = ThisDate.getYear();
if (y < 1000) y += 1900;
var m = ThisDate.getMonth() + 1;
var z = ThisDate.getDate();
// if ((m==1) || (m==2)) {
// y -= 1;
// m += 12; }
var A = y / 100;
var B = 2 - A + (A/4);
var C = 365.25 * y;
var D = 30.6001 * (m+1);
var JD = B + C + D + z + 1720994.5;
//End julian_date
var T = (JD - 2451545) / 36525;
var T0 = ((((T + 2.5862E-5) * T) + 2400.051336) * T) + 6.697374558;
T0 = T0 % 24;
if (T0 < 0) T0 += 24;
var UT = ThisDate.getHours() + ((ThisDate.getMinutes() + (ThisDate.getSeconds() / 60)) / 60);
T0 += UT * 1.002737909;
T0 = T0 % 24;
if (T0 < 0) T0 += 24;
//End GST
var tmp = alpha - ((TWOPI/24)*T0);
while (tmp < -Math.PI) {tmp += TWOPI;};
while (tmp > Math.PI) {tmp -= TWOPI;};
var lon = tmp * (360/TWOPI);
var lat = delta * (360/TWOPI);
//Generate the path of the appropriate xearth image
//lon is even
lon = Math.round(lon);
//if (lon & 1 != 0) {
if (lon % 2 != 0) {
if (lon > 0) {
lon -= 1;
}
else {
lon += 1;
}
}
// force even for mozilla 4.01-4.05
// Consolidate lines, 4/5/01 - PRF
lon = Math.round(lon/2) * 2;
if (lon <= -181) lon = -180;
if (lon >= 181) lon = 180;
//lat is odd
lat = Math.round(lat);
//if (lat & 1 == 0) {
if (lat % 2 == 0) {
if (lat > 0) {
lat -= 1;
}
else {
lat += 1;
}
}
// force odd for mozilla 4.01-4.05
// Fixed broken algorithm, 4/5/01 - PRF
lat = (Math.round(lat/2 - 1) * 2) + 1;
if (lat <= -24) lat = -23;
if (lat >= 24) lat = 23;
var latStr; var lonStr;
if (lat < 0)
latStr = (-lat) + "S";
else
latStr = lat + "N";
if (lon < 0)
lonStr = (-lon) + "S";
else
lonStr = lon + "N";
return "images/xearths/" + latStr + "/" + lonStr + ".jpg";
//return lon;
}
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