decpl=4 
//**************CD****************
function ClearFormCD(){
    document.InputFormCD.lat1.value = "0:00.00";
    document.InputFormCD.lat2.value = "0:00.00";
    document.InputFormCD.lon1.value = "0:00.00";
    document.InputFormCD.lon2.value = "0:00.00";
    document.OutputFormCD.crs12.value = "";
    document.OutputFormCD.crs21.value = "";
    document.OutputFormCD.d12.value = "";
}
function ComputeFormCD(){
var signlat1,signlat2,signlon1,signlon2,dc
var lat1,lat2,lon1,lon2
var d,crs12,crs21
var argacos
var a,invf
signlat1=signlatlon(document.InputFormCD.NS1)
signlat2=signlatlon(document.InputFormCD.NS2)
signlon1=signlatlon(document.InputFormCD.EW1)
signlon2=signlatlon(document.InputFormCD.EW2)
lat1=(Math.PI/180)*signlat1*checkField(document.InputFormCD.lat1)
lat2=(Math.PI/180)*signlat2*checkField(document.InputFormCD.lat2)
lon1=(Math.PI/180)*signlon1*checkField(document.InputFormCD.lon1)
lon2=(Math.PI/180)*signlon2*checkField(document.InputFormCD.lon2)
dc=dconv(document.OutputFormCD.Dunit) 
ellipse=getEllipsoid(document.OutputFormCD.Model)
if (ellipse.name=="Sphere"){
  cd=crsdist(lat1,lon1,lat2,lon2)
  crs12 =cd.crs12*(180/Math.PI)
  crs21 =cd.crs21*(180/Math.PI)
  d=cd.d*(180/Math.PI)*60*dc
  } else {
  cde=crsdist_ell(lat1,-lon1,lat2,-lon2,ellipse)
  crs12 =cde.crs12*(180/Math.PI)
  crs21 =cde.crs21*(180/Math.PI)
  d=cde.d*dc
  }
document.OutputFormCD.crs12.value=crs12
document.OutputFormCD.crs21.value=crs21
document.OutputFormCD.d12.value=d
}
function crsdist(lat1,lon1,lat2,lon2){ 
if ((lat1+lat2==0.) && (Math.abs(lon1-lon2)==Math.PI)
                    && (Math.abs(lat1) != (Math.PI/180)*90.)){
    alert("Course between antipodal points is undefined")
    }
with (Math){
  d=acos(sin(lat1)*sin(lat2)+cos(lat1)*cos(lat2)*cos(lon1-lon2))
  if ((d==0.) || (lat1==-(PI/180)*90.)){
     crs12=2*PI
  } else if (lat1==(PI/180)*90.){
     crs12=PI
  } else {
     argacos=(sin(lat2)-sin(lat1)*cos(d))/(sin(d)*cos(lat1))
     if (sin(lon2-lon1) < 0){
       crs12=acosf(argacos)
     }
     else{
       crs12=2*PI-acosf(argacos)
     }
  }
  if ((d==0.) || (lat2==-(PI/180)*90.)){
     crs21=0.
  } else if (lat2==(PI/180)*90.){
     crs21=PI
  }else{
     argacos=(sin(lat1)-sin(lat2)*cos(d))/(sin(d)*cos(lat2))
     if (sin(lon1-lon2)<0){
       crs21=acosf(argacos)
     }
     else{
       crs21=2*PI-acosf(argacos)
     }
  }
}
out=new MakeArray(0)
out.d=d
out.crs12=crs12
out.crs21=crs21
return out
}
function crsdist_ell(glat1,glon1,glat2,glon2,ellipse){
a=ellipse.a
f=1/ellipse.invf
var r, tu1, tu2, cu1, su1, cu2, s1, b1, f1
var x, sx, cx, sy, cy,y, sa, c2a, cz, e, c, d
var EPS= 0.00000000005
var faz, baz, s
var iter=1
var MAXITER=100
  if ((glat1+glat2==0.) && (Math.abs(glon1-glon2)==Math.PI)){
    alert("Course and distance between antipodal points is undefined")
    glat1=glat1+0.00001
    }
  if (glat1==glat2 && (glon1==glon2 || Math.abs(Math.abs(glon1-glon2)-2*Math.PI) <  EPS)){
    alert("Points 1 and 2 are identical- course undefined")
    out=new MakeArray(0)
    out.d=0
    out.crs12=0
    out.crs21=Math.PI
    return out
  }
  r = 1 - f
  tu1 = r * Math.tan (glat1)
  tu2 = r * Math.tan (glat2)
  cu1 = 1. / Math.sqrt (1. + tu1 * tu1)
  su1 = cu1 * tu1
  cu2 = 1. / Math.sqrt (1. + tu2 * tu2)
  s1 = cu1 * cu2
  b1 = s1 * tu2
  f1 = b1 * tu1
  x = glon2 - glon1
  d = x + 1
  while ((Math.abs(d - x) > EPS) && (iter < MAXITER))
    {
      iter=iter+1
      sx = Math.sin (x)
      cx = Math.cos (x)
      tu1 = cu2 * sx
      tu2 = b1 - su1 * cu2 * cx
      sy = Math.sqrt(tu1 * tu1 + tu2 * tu2)
      cy = s1 * cx + f1
      y = atan2 (sy, cy)
      sa = s1 * sx / sy
      c2a = 1 - sa * sa
      cz = f1 + f1
      if (c2a > 0.)
	cz = cy - cz / c2a
      e = cz * cz * 2. - 1.
      c = ((-3. * c2a + 4.) * f + 4.) * c2a * f / 16.
      d = x
      x = ((e * cy * c + cz) * sy * c + y) * sa
      x = (1. - c) * x * f + glon2 - glon1
    }
  faz = modcrs(atan2(tu1, tu2))
  baz = modcrs(atan2(cu1 * sx, b1 * cx - su1 * cu2) + Math.PI)
  x = Math.sqrt ((1 / (r * r) - 1) * c2a + 1)
  x +=1
  x = (x - 2.) / x
  c = 1. - x
  c = (x * x / 4. + 1.) / c
  d = (0.375 * x * x - 1.) * x
  x = e * cy
  s = ((((sy*sy*4.-3.)*(1.-e-e)*cz*d/6.-x)*d/4.+cz)*sy*d+y)*c*a*r
  out=new MakeArray(0)
  out.d=s
  out.crs12=faz
  out.crs21=baz
  if (Math.abs(iter-MAXITER)<EPS){
    alert("Algorithm did not converge")
  }
  return out

}
function ClearFormDir(){
    document.InputFormDir.lat1.value = "0:00.00";
    document.InputFormDir.crs12.value = "360";
    document.InputFormDir.lon1.value = "0:00.00";
    document.InputFormDir.d12.value = "0.0";
    document.OutputFormDir.lat2.value = "";
    document.OutputFormDir.lat2ns.value = "N";
    document.OutputFormDir.lon2.value = "";
    document.OutputFormDir.lon2ew.value = "E";
}
function ComputeFormDir(){
var signlat1,signlon1,dc
var lat1,lon1
var d12,crs12
var a,invf
signlat1=signlatlon(document.InputFormDir.NS1)
signlon1=signlatlon(document.InputFormDir.EW1)
lat1=(Math.PI/180)*signlat1*checkField(document.InputFormDir.lat1)
lon1=(Math.PI/180)*signlon1*checkField(document.InputFormDir.lon1)
d12=document.InputFormDir.d12.value
dc=dconv(document.OutputFormDir.Dunit)
d12 /=dc  
crs12=document.InputFormDir.crs12.value*Math.PI/180. 
ellipse=getEllipsoid(document.OutputFormDir.Model) //get ellipse
if (ellipse.name=="Sphere"){
  d12 /=(180*60/Math.PI)
  cd=direct(lat1,lon1,crs12,d12)
  lat2 =cd.lat*(180/Math.PI)
  lon2 =cd.lon*(180/Math.PI)
  } else {
  cde=direct_ell(lat1,-lon1,crs12,d12,ellipse)
  lat2 =cde.lat*(180/Math.PI)
  lon2 =-cde.lon*(180/Math.PI)
  }
if (lat2 >=0) {
   document.OutputFormDir.lat2ns.value="N"
   } else {
   document.OutputFormDir.lat2ns.value="S"
   }
if (lon2 > 0) {
   document.OutputFormDir.lon2ew.value="W"
   } else {
   document.OutputFormDir.lon2ew.value="E"
   }
lat2s=degtodm(Math.abs(lat2),decpl)
document.OutputFormDir.lat2.value=lat2s
lon2s=degtodm(Math.abs(lon2),decpl)
document.OutputFormDir.lon2.value=lon2s
}
function direct(lat1,lon1,crs12,d12) {
  var EPS= 0.00000000005
  var dlon,lat,lon
  if ((Math.abs(Math.cos(lat1))<EPS) && !(Math.abs(Math.sin(crs12))<EPS)){
    alert("Only N-S courses are meaningful, starting at a pole!")
  }
  lat=Math.asin(Math.sin(lat1)*Math.cos(d12)+
                Math.cos(lat1)*Math.sin(d12)*Math.cos(crs12))
  if (Math.abs(Math.cos(lat))<EPS){
    lon=0.;
  }else{
    dlon=Math.atan2(Math.sin(crs12)*Math.sin(d12)*Math.cos(lat1),
                  Math.cos(d12)-Math.sin(lat1)*Math.sin(lat))
    lon=mod( lon1-dlon+Math.PI,2*Math.PI )-Math.PI
  }
  out=new MakeArray(0)
  out.lat=lat
  out.lon=lon
  return out
}
function direct_ell(glat1,glon1,faz,s,ellipse) {
var EPS= 0.00000000005
var r, tu, sf, cf, b, cu, su, sa, c2a, x, c, d, y, sy, cy, cz, e
var glat2,glon2,baz,f
  if ((Math.abs(Math.cos(glat1))<EPS) && !(Math.abs(Math.sin(faz))<EPS)){
    alert("Only N-S courses are meaningful, starting at a pole!")
  }
  a=ellipse.a
  f=1/ellipse.invf
  r = 1 - f
  tu = r * Math.tan (glat1)
  sf = Math.sin (faz)
  cf = Math.cos (faz)
  if (cf==0){
     b=0.
  }else{
     b=2. * atan2 (tu, cf)
  }
  cu = 1. / Math.sqrt (1 + tu * tu)
  su = tu * cu
  sa = cu * sf
  c2a = 1 - sa * sa
  x = 1. + Math.sqrt (1. + c2a * (1. / (r * r) - 1.))
  x = (x - 2.) / x
  c = 1. - x
  c = (x * x / 4. + 1.) / c
  d = (0.375 * x * x - 1.) * x
  tu = s / (r * a * c)
  y = tu
  c = y + 1
  while (Math.abs (y - c) > EPS)
    {
      sy = Math.sin (y)
      cy = Math.cos (y)
      cz = Math.cos (b + y)
      e = 2. * cz * cz - 1.
      c = y
      x = e * cy
      y = e + e - 1.
      y = (((sy * sy * 4. - 3.) * y * cz * d / 6. + x) *
              d / 4. - cz) * sy * d + tu
    }
  b = cu * cy * cf - su * sy
  c = r * Math.sqrt (sa * sa + b * b)
  d = su * cy + cu * sy * cf
  glat2 = modlat(atan2 (d, c))
  c = cu * cy - su * sy * cf
  x = atan2 (sy * sf, c)
  c = ((-3. * c2a + 4.) * f + 4.) * c2a * f / 16.
  d = ((e * cy * c + cz) * sy * c + y) * sa
  glon2 = modlon(glon1 + x - (1. - c) * d * f)	// fix date line problems
  baz = modcrs(atan2 (sa, b) + Math.PI)
  out=new MakeArray(0)
  out.lat=glat2
  out.lon=glon2
  out.crs21=baz
  return out
}
function Link(){
type=new MakeArray(3)
type[1]="airport-info"
type[2]="navaid-info"
type[3]="fix-info"
var query=type[document.spheroid.Fixtype.selectedIndex+1]
var ref="http://www.airnav.com/cgi-bin/"+query+"?"+
 document.spheroid.Fix.value
var  newWindow=window.open(ref,"")
     newWindow=window.open(ref,"")  //twice because of Netscape bug
}
function signlatlon(selection){
var sign
if (selection.selectedIndex==0){
   sign=1
}else{
   sign=-1
}
return sign
}

function MakeArray(n){
   this.length=n
   for (var i=1;i<=n;i++){
     this[i]=0
   }
   return this
}

function dconv(selection){
   dc=new MakeArray(3)
   dc[1]=1.
   dc[2]=1.852 //km
   dc[3]=1.150779448 //sm
   return dc[selection.selectedIndex+1]
}
function ellipsoid(name, a, invf){
  /* constructor */
  this.name=name
  this.a=a
  this.invf=invf
}
function getEllipsoid(selection){
  no_selections=10
  ells= new MakeArray(no_selections)
  ells[1]= new ellipsoid("Sphere", 180*60/Math.PI,"Infinite")
  ells[2]= new ellipsoid("WGS84",6378.137/1.852,298.257223563)
  ells[3]= new ellipsoid("NAD27",6378.2064/1.852,294.9786982138)
  ells[4]= new ellipsoid("International",6378.388/1.852,297.0)
  ells[5]= new ellipsoid("Krasovsky",6378.245/1.852,298.3)
  ells[6]= new ellipsoid("Bessel",6377.397155/1.852,299.1528)
  ells[7]= new ellipsoid("WGS72",6378.135/1.852,298.26)
  ells[8]= new ellipsoid("WGS66",6378.145/1.852,298.25)
  ells[9]= new ellipsoid("FAI sphere",6371.0/1.852,1000000000.)
  ells[10]= new ellipsoid("User",0.,0.)
  if (selection.selectedIndex+1==no_selections){
    ells[no_selections].name="User"
    ells[no_selections].a= document.spheroid.major_radius.value/1.852
    ells[no_selections].invf=document.spheroid.inverse_f.value
    if (ells[no_selections].invf=="Infinite"){
       ells[no_selections].invf=1000000000.
    }
  } else {
  }
  return ells[selection.selectedIndex+1]
}
function parselatlon(instr){
var deg,min,sec,colonIndex,degstr,minstr,str
str=instr
colonIndex=str.indexOf(":")
if (colonIndex==-1){
   if (!isPosNumber(str)){
      badLLFormat(instr)
   return 0.
   } else {
   return parseFloat(str)
   }
}
degstr=str.substring(0,colonIndex)
str=str.substring(colonIndex+1,str.length)
if (!isPosInteger(degstr)){
   badLLFormat(instr)
   return 0.
} else {
   deg=parseFloat(degstr+".0")
}
colonIndex=str.indexOf(":")
if (colonIndex==-1){ // dd:mm.mm?
   if (!isPosNumber(str)){
      badLLFormat(instr)
      return 0.
   } else {
   min=parseFloat(str)
   if (min < 60.){
     return deg+parseFloat(str)/60.
   } else {
   badLLFormat(instr)
      return 0.
   }
   }
}
minstr=str.substring(0,colonIndex)+".0" 
str=str.substring(colonIndex+1,str.length)
if (!isPosNumber(minstr) || !isPosNumber(str)){
  badLLFormat(instr)
  return 0.
} else {
  if ( (parseFloat(minstr) < 60) && (parseFloat(str) < 60.)){
    return deg+ parseFloat(minstr)/60.+parseFloat(str)/3600.
  } else {
    badLLFormat(instr)
    return 0.
  }
}
}
function badLLFormat(str){
alert(str+ " is an invalid lat/lon format\n"+
            "Use DD.DD DD:MM.MM or DD:MM:SS.SS")
}
function isPosInteger(instr){
str=""+instr
for (var i=0;i<str.length;i++) {
  var oneChar=str.charAt(i)
  if (oneChar < "0" || oneChar > "9") {
    return false
  }
}
return true
}
function isPosNumber(instr){
str=""+instr
oneDecimal=false
for (var i=0;i<str.length;i++) {
  var oneChar=str.charAt(i)
  if (oneChar=="." && !oneDecimal){
     oneDecimal=true
     continue
  }
  if (oneChar < "0" || oneChar > "9") {
    return false
  }
}
return true
}
function checkField(field){
var str=field.name
var latlon
latlon=parselatlon(field.value)
if (str.substring(0,3)=="lat") {
   if (latlon > 90.) {
      alert ("Latitudes cannot exceed 90 degrees")
      field.focus()
      field.select()
   }
}
if (str.substring(0,3)=="lon") {
   if (latlon > 180.) {
      alert ("Longitudes cannot exceed 180 degrees")
      field.focus()
      field.select()
   }
}
return latlon
}
function acosf(x){
if (Math.abs(x) >1){
    x /=Math.abs(x)
  }
return Math.acos(x)
}
function atan2(y,x){
var out
  if (x <0)            { out= Math.atan(y/x)+Math.PI}
  if ((x >0) && (y>=0)){ out= Math.atan(y/x)}
  if ((x >0) && (y<0)) { out= Math.atan(y/x)+2*Math.PI}
  if ((x==0) && (y>0)) { out= Math.PI/2}
  if ((x==0) && (y<0)) { out= 3*Math.PI/2}
  if ((x==0) && (y==0)) {
    alert("atan2(0,0) undefined")
    out= 0.
  }
  return out
}
function mod(x,y){
  return x-y*Math.floor(x/y)
}
function modlon(x){
  return mod(x+Math.PI,2*Math.PI)-Math.PI
}
function modcrs(x){
  return mod(x,2*Math.PI)
}

function modlat(x){
  return mod(x+Math.PI/2,2*Math.PI)-Math.PI/2
}
function degtodm(deg,decplaces){
var deg1=Math.floor(deg)
var min=60.*(deg-Math.floor(deg))
var mins=format(min,decplaces)
if (mins.substring(0,1)=="6" && mins >59.0){
  deg1 +=1
  mins=format(0,decplaces)
}
return deg1+":"+mins
}
function format(expr, decplaces){
var str= "" +Math.round(eval(expr)*Math.pow(10,decplaces))
while (str.length <=decplaces) {
  str= "0" + str
}
var decpoint=str.length-decplaces
return str.substring(0,decpoint)+"."+str.substring(decpoint,str.length)
}
function showProps(obj,objName){
var result=""
for (var i in obj){
result +=objName + "." + i + " = " + obj[i] + "\n"
}
alert(result)
}