/*
Call generic wms service for GoogleMaps v2
John Deck, UC Berkeley
Inspiration & Code from:
	Mike Williams http://www.econym.demon.co.uk/googlemaps2/ V2 Reference & custommap code
	Brian Flood http://www.spatialdatalogic.com/cs/blogs/brian_flood/archive/2005/07/11/39.aspx V1 WMS code
	Kyle Mulka http://blog.kylemulka.com/?p=287  V1 WMS code modifications
	http://search.cpan.org/src/RRWO/GPS-Lowrance-0.31/lib/Geo/Coordinates/MercatorMeters.pm
	
The code portion of projection tranfer is downloaded from SUPPORT.ESRI.COM.
*/

var pi = 3.14159265358979;
/* Ellipsoid model constants (actual values here are for WGS84) */
var sm_a = 6378137.0;
var sm_b = 6356752.314;
var sm_EccSquared = 6.69437999013e-03;
var UTMScaleFactor = 0.9996;
var MAGIC_NUMBER=6356752.3142;
var DEG2RAD=0.0174532922519943;

function dd2MercMetersLng(p_lng) { 
	return (MAGIC_NUMBER*(p_lng*DEG2RAD)); 
}

function dd2MercMetersLat(p_lat) {
	if (p_lat >= 85) p_lat=85;
	if (p_lat <= -85) p_lat=-85;
	return MAGIC_NUMBER*Math.log(Math.tan(((p_lat*DEG2RAD)+(PI/2)) /2));
}

CustomGetTileUrl=function(a,b,c) {
	var lULP = new GPoint(a.x*256,(a.y+1)*256);
	var lLRP = new GPoint((a.x+1)*256,a.y*256);
	var lUL = G_NORMAL_MAP.getProjection().fromPixelToLatLng(lULP,b,c);
	var lLR = G_NORMAL_MAP.getProjection().fromPixelToLatLng(lLRP,b,c);

	// Convert from LongitudeLatitude to Mercator
	//if (this.myMercZoomLevel>1 && (map.getZoom() < this.myMercZoomLevel)) {
	if (this.myMercZoomLevel>1) {
		var UpperLeft = LLToUTM(lUL.x, lUL.y)
		var LowerRight = LLToUTM(lLR.x, lLR.y)
		var uXY = UpperLeft.split("|");
		var uX = uXY[0];
		var uY = uXY[1];
		
		var uXY2 = LowerRight.split("|");
		var uX2= uXY2[0];
		var uY2 = uXY2[1];

		var lBbox = uX + "," + uY + "," + uX2 + "," + uY2;
		//alert(lBbox);
		
		var lSRS="EPSG:26917";
	} else {
		var lBbox=lUL.x+","+lUL.y+","+lLR.x+","+lLR.y;
		//alert(lBbox);
		var lSRS="EPSG:4326";
	}
	var lURL=this.myBaseURL;
	
	if (this.MyBuild = 1) {
		lURL+="&REQUEST=GetMap";
		lURL+="&SERVICE=WMS";
		lURL+="&VERSION=1.1.1";
		lURL+="&LAYERS="+this.myLayers;
		lURL+="&STYLES="+this.myStyles; 
		lURL+="&FORMAT="+this.myFormat;
		lURL+="&BGCOLOR=0xFFFFFF";
		lURL+="&TRANSPARENT=TRUE";
		lURL+="&SRS="+lSRS;
		lURL+="&BBOX="+lBbox;
		lURL+="&WIDTH=256";
		lURL+="&HEIGHT=256";
		lURL+="&reaspect=false";
	}
	return lURL;
}

/*///////////////////////////////////////////////////////////////
* This following portion code is used to do projection transfer between UTM and LatitideLongitude
*/
// /////////////////////////////////////////////////////

// DegToRad:    Converts degrees to radians.
function DegToRad (deg){
    return (deg / 180.0 * pi)
}

// RadToDeg:  Converts radians to degrees.
function RadToDeg (rad){
    return (rad / pi * 180.0)
}

/*
* ArcLengthOfMeridian
* Computes the ellipsoidal distance from the equator to a point at a given latitude.
* Reference: Hoffmann-Wellenhof, B., Lichtenegger, H., and Collins, J.,
* GPS: Theory and Practice, 3rd ed.  New York: Springer-Verlag Wien, 1994.
* Inputs:
*     phi - Latitude of the point, in radians.
* Globals:
*     sm_a - Ellipsoid model major axis.
*     sm_b - Ellipsoid model minor axis.
* Returns:
*     The ellipsoidal distance of the point from the equator, in meters.
*/
function ArcLengthOfMeridian (phi){
	var alpha, beta, gamma, delta, epsilon, n;
	var result;

	/* Precalculate n */
	n = (sm_a - sm_b) / (sm_a + sm_b);
	
	/* Precalculate alpha */
	alpha = ((sm_a + sm_b) / 2.0) * (1.0 + (Math.pow (n, 2.0) / 4.0) + (Math.pow (n, 4.0) / 64.0));
	
	/* Precalculate beta */
	beta = (-3.0 * n / 2.0) + (9.0 * Math.pow (n, 3.0) / 16.0) + (-3.0 * Math.pow (n, 5.0) / 32.0);
	
	/* Precalculate gamma */
	gamma = (15.0 * Math.pow (n, 2.0) / 16.0) + (-15.0 * Math.pow (n, 4.0) / 32.0);
	
	/* Precalculate delta */
	delta = (-35.0 * Math.pow (n, 3.0) / 48.0) + (105.0 * Math.pow (n, 5.0) / 256.0);
	
	/* Precalculate epsilon */
	epsilon = (315.0 * Math.pow (n, 4.0) / 512.0);

  	/* Now calculate the sum of the series and return */
   	result = alpha * (phi + (beta * Math.sin (2.0 * phi)) + (gamma * Math.sin (4.0 * phi)) + (delta * Math.sin (6.0 * phi)) + (epsilon * Math.sin (8.0 * phi)));

   	return  result;
}

/*
* UTMCentralMeridian
* Determines the central meridian for the given UTM zone.
* Inputs:
*     zone - An integer value designating the UTM zone, range [1,60].
* Returns:
*   The central meridian for the given UTM zone, in radians, or zero
*   if the UTM zone parameter is outside the range [1,60].
*   Range of the central meridian is the radian equivalent of [-177,+177].
*/
function UTMCentralMeridian (zone){
    var cmeridian;
    cmeridian = DegToRad (-183.0 + (zone * 6.0));
    return cmeridian;
}

/*
* FootpointLatitude
* Computes the footpoint latitude for use in converting transverse
* Mercator coordinates to ellipsoidal coordinates.
* Reference: Hoffmann-Wellenhof, B., Lichtenegger, H., and Collins, J.,
*   GPS: Theory and Practice, 3rd ed.  New York: Springer-Verlag Wien, 1994.
* Inputs:
*   y - The UTM northing coordinate, in meters.
* Returns:
*   The footpoint latitude, in radians.
*/

function FootpointLatitude (y){
	var y_, alpha_, beta_, gamma_, delta_, epsilon_, n;
	var result;
	
	/* Precalculate n (Eq. 10.18) */
	n = (sm_a - sm_b) / (sm_a + sm_b);
	
	/* Precalculate alpha_ (Eq. 10.22) */
	/* (Same as alpha in Eq. 10.17) */
	alpha_ = ((sm_a + sm_b) / 2.0) * (1 + (Math.pow (n, 2.0) / 4) + (Math.pow (n, 4.0) / 64));
	
	/* Precalculate y_ (Eq. 10.23) */
	y_ = y / alpha_;
	
	/* Precalculate beta_ (Eq. 10.22) */
	beta_ = (3.0 * n / 2.0) + (-27.0 * Math.pow (n, 3.0) / 32.0) + (269.0 * Math.pow (n, 5.0) / 512.0);
	
	/* Precalculate gamma_ (Eq. 10.22) */
	gamma_ = (21.0 * Math.pow (n, 2.0) / 16.0) + (-55.0 * Math.pow (n, 4.0) / 32.0);
	
	/* Precalculate delta_ (Eq. 10.22) */
	delta_ = (151.0 * Math.pow (n, 3.0) / 96.0)  + (-417.0 * Math.pow (n, 5.0) / 128.0);
	
	/* Precalculate epsilon_ (Eq. 10.22) */
	epsilon_ = (1097.0 * Math.pow (n, 4.0) / 512.0);
	
	/* Now calculate the sum of the series (Eq. 10.21) */
	result = y_ + (beta_ * Math.sin (2.0 * y_)) + (gamma_ * Math.sin (4.0 * y_)) + (delta_ * Math.sin (6.0 * y_)) + (epsilon_ * Math.sin (8.0 * y_));

	return  result;
}

/*
* MapLatLonToXY
* Converts a latitude/longitude pair to x and y coordinates in the
* Transverse Mercator projection.  Note that Transverse Mercator is not
* the same as UTM; a scale factor is required to convert between them.
* Reference: Hoffmann-Wellenhof, B., Lichtenegger, H., and Collins, J.,
* GPS: Theory and Practice, 3rd ed.  New York: Springer-Verlag Wien, 1994.
* Inputs:
*    phi - Latitude of the point, in radians.
*    lambda - Longitude of the point, in radians.
*    lambda0 - Longitude of the central meridian to be used, in radians.
* Outputs:
*    xy - A 2-element array containing the x and y coordinates
*     of the computed point.
* Returns:
*    The function does not return a value.
*/
function MapLatLonToXY (phi, lambda, lambda0, xy){
	var N, nu2, ep2, t, t2, l;
	var l3coef, l4coef, l5coef, l6coef, l7coef, l8coef;
	var tmp;
	
	/* Precalculate ep2 */
	ep2 = (Math.pow (sm_a, 2.0) - Math.pow (sm_b, 2.0)) / Math.pow (sm_b, 2.0);
	
	/* Precalculate nu2 */
	nu2 = ep2 * Math.pow (Math.cos (phi), 2.0);
	
	/* Precalculate N */
	N = Math.pow (sm_a, 2.0) / (sm_b * Math.sqrt (1 + nu2));
	
	/* Precalculate t */
	t = Math.tan (phi);
	t2 = t * t;
	tmp = (t2 * t2 * t2) - Math.pow (t, 6.0);
	
	/* Precalculate l */
	l = lambda - lambda0;
	
	/* Precalculate coefficients for l**n in the equations below
	   so a normal human being can read the expressions for easting
	   and northing
	   -- l**1 and l**2 have coefficients of 1.0 
	*/
	l3coef = 1.0 - t2 + nu2;
	
	l4coef = 5.0 - t2 + 9 * nu2 + 4.0 * (nu2 * nu2);
	
	l5coef = 5.0 - 18.0 * t2 + (t2 * t2) + 14.0 * nu2 - 58.0 * t2 * nu2;
	
	l6coef = 61.0 - 58.0 * t2 + (t2 * t2) + 270.0 * nu2 - 330.0 * t2 * nu2;
	
	l7coef = 61.0 - 479.0 * t2 + 179.0 * (t2 * t2) - (t2 * t2 * t2);
	
	l8coef = 1385.0 - 3111.0 * t2 + 543.0 * (t2 * t2) - (t2 * t2 * t2);
	
	/* Calculate easting (x) */
	xy[0] = N * Math.cos (phi) * l + (N / 6.0 * Math.pow (Math.cos (phi), 3.0) * l3coef * Math.pow (l, 3.0))
		+ (N / 120.0 * Math.pow (Math.cos (phi), 5.0) * l5coef * Math.pow (l, 5.0))
		+ (N / 5040.0 * Math.pow (Math.cos (phi), 7.0) * l7coef * Math.pow (l, 7.0));
	
	/* Calculate northing (y) */
	xy[1] = ArcLengthOfMeridian (phi)
		+ (t / 2.0 * N * Math.pow (Math.cos (phi), 2.0) * Math.pow (l, 2.0))
		+ (t / 24.0 * N * Math.pow (Math.cos (phi), 4.0) * l4coef * Math.pow (l, 4.0))
		+ (t / 720.0 * N * Math.pow (Math.cos (phi), 6.0) * l6coef * Math.pow (l, 6.0))
		+ (t / 40320.0 * N * Math.pow (Math.cos (phi), 8.0) * l8coef * Math.pow (l, 8.0));
	
	return;
}

/*
* MapXYToLatLon
* Converts x and y coordinates in the Transverse Mercator projection to
* a latitude/longitude pair.  Note that Transverse Mercator is not
* the same as UTM; a scale factor is required to convert between them.
* Reference: Hoffmann-Wellenhof, B., Lichtenegger, H., and Collins, J.,
*   GPS: Theory and Practice, 3rd ed.  New York: Springer-Verlag Wien, 1994.
* Inputs:
*   x - The easting of the point, in meters.
*   y - The northing of the point, in meters.
*   lambda0 - Longitude of the central meridian to be used, in radians.
* Outputs:
*   philambda - A 2-element containing the latitude and longitude
*           in radians.
* Returns:
*   The function does not return a value.
* Remarks:
*   The local variables Nf, nuf2, tf, and tf2 serve the same purpose as
*   N, nu2, t, and t2 in MapLatLonToXY, but they are computed with respect
*   to the footpoint latitude phif.
*   x1frac, x2frac, x2poly, x3poly, etc. are to enhance readability and
*   to optimize computations.
*/
function MapXYToLatLon (x, y, lambda0, philambda){
    var phif, Nf, Nfpow, nuf2, ep2, tf, tf2, tf4, cf;
    var x1frac, x2frac, x3frac, x4frac, x5frac, x6frac, x7frac, x8frac;
    var x2poly, x3poly, x4poly, x5poly, x6poly, x7poly, x8poly;

    /* Get the value of phif, the footpoint latitude. */
    phif = FootpointLatitude (y);

    /* Precalculate ep2 */
    ep2 = (Math.pow (sm_a, 2.0) - Math.pow (sm_b, 2.0)) / Math.pow (sm_b, 2.0);

    /* Precalculate cos (phif) */
    cf = Math.cos (phif);

    /* Precalculate nuf2 */
    nuf2 = ep2 * Math.pow (cf, 2.0);

    /* Precalculate Nf and initialize Nfpow */
    Nf = Math.pow (sm_a, 2.0) / (sm_b * Math.sqrt (1 + nuf2));
    Nfpow = Nf;

    /* Precalculate tf */
    tf = Math.tan (phif);
    tf2 = tf * tf;
    tf4 = tf2 * tf2;

    /* Precalculate fractional coefficients for x**n in the equations
			below to simplify the expressions for latitude and longitude. */
    x1frac = 1.0 / (Nfpow * cf);

    Nfpow *= Nf;   /* now equals Nf**2) */
    x2frac = tf / (2.0 * Nfpow);

    Nfpow *= Nf;   /* now equals Nf**3) */
    x3frac = 1.0 / (6.0 * Nfpow * cf);

    Nfpow *= Nf;   /* now equals Nf**4) */
    x4frac = tf / (24.0 * Nfpow);

    Nfpow *= Nf;   /* now equals Nf**5) */
    x5frac = 1.0 / (120.0 * Nfpow * cf);

    Nfpow *= Nf;   /* now equals Nf**6) */
    x6frac = tf / (720.0 * Nfpow);

    Nfpow *= Nf;   /* now equals Nf**7) */
    x7frac = 1.0 / (5040.0 * Nfpow * cf);

    Nfpow *= Nf;   /* now equals Nf**8) */
    x8frac = tf / (40320.0 * Nfpow);

    /* Precalculate polynomial coefficients for x**n.
			-- x**1 does not have a polynomial coefficient. */
    x2poly = -1.0 - nuf2;

    x3poly = -1.0 - 2 * tf2 - nuf2;

    x4poly = 5.0 + 3.0 * tf2 + 6.0 * nuf2 - 6.0 * tf2 * nuf2 - 3.0 * (nuf2 *nuf2) - 9.0 * tf2 * (nuf2 * nuf2);

    x5poly = 5.0 + 28.0 * tf2 + 24.0 * tf4 + 6.0 * nuf2 + 8.0 * tf2 * nuf2;

    x6poly = -61.0 - 90.0 * tf2 - 45.0 * tf4 - 107.0 * nuf2 + 162.0 * tf2 * nuf2;

    x7poly = -61.0 - 662.0 * tf2 - 1320.0 * tf4 - 720.0 * (tf4 * tf2);

    x8poly = 1385.0 + 3633.0 * tf2 + 4095.0 * tf4 + 1575 * (tf4 * tf2);

    /* Calculate latitude */
    philambda[0] = phif + x2frac * x2poly * (x * x) + x4frac * x4poly * Math.pow (x, 4.0) + x6frac * x6poly * Math.pow (x, 6.0) + x8frac * x8poly * Math.pow (x, 8.0);

    /* Calculate longitude */
    philambda[1] = lambda0 + x1frac * x + x3frac * x3poly * Math.pow (x, 3.0) + x5frac * x5poly * Math.pow (x, 5.0) + x7frac * x7poly * Math.pow (x, 7.0);

    return;
}

/*
* LatLonToUTMXY
* Converts a latitude/longitude pair to x and y coordinates in the
* Universal Transverse Mercator projection.
* Inputs:
*   lat - Latitude of the point, in radians.
*   lon - Longitude of the point, in radians.
*   zone - UTM zone to be used for calculating values for x and y.
*      If zone is less than 1 or greater than 60, the routine
*      will determine the appropriate zone from the value of lon.
* Outputs:
*   xy - A 2-element array where the UTM x and y values will be stored.
* Returns:
*   The UTM zone used for calculating the values of x and y.
*/
function LatLonToUTMXY (lat, lon, zone, xy){
    MapLatLonToXY (lat, lon, UTMCentralMeridian (zone), xy);

    /* Adjust easting and northing for UTM system. */
    xy[0] = xy[0] * UTMScaleFactor + 500000.0;
	//xy[0] = xy[0] * UTMScaleFactor + 500050.0;
    xy[1] = xy[1] * UTMScaleFactor;
    if (xy[1] < 0.0)
        xy[1] = xy[1] + 10000000.0;

    return zone;
}

/*
* UTMXYToLatLon
* Converts x and y coordinates in the Universal Transverse Mercator
* projection to a latitude/longitude pair.
* Inputs:
*	x - The easting of the point, in meters.
*	y - The northing of the point, in meters.
*	zone - The UTM zone in which the point lies.
*	southhemi - True if the point is in the southern hemisphere;
*           false otherwise.
* Outputs:
*	latlon - A 2-element array containing the latitude and
*        longitude of the point, in radians.
* Returns:
*	The function does not return a value.
*/
function UTMXYToLatLon (x, y, zone, southhemi, latlon){
    var cmeridian;

    x -= 500000.0;
    x /= UTMScaleFactor;

    /* If in southern hemisphere, adjust y accordingly. */
    if (southhemi)
    y -= 10000000.0;

    y /= UTMScaleFactor;

    cmeridian = UTMCentralMeridian (zone);
    MapXYToLatLon (x, y, cmeridian, latlon);

    return;
}

function LLToUTM (lon, lat){
    var xy = new Array(2);

    // Compute the UTM zone.
    zone = Math.floor ((lon + 180.0) / 6) + 1

    zone = LatLonToUTMXY (DegToRad (lat), DegToRad (lon), 17, xy);
    var uX = xy[0];
    var uY = xy[1];
		return uX + "|" + uY;
}