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Champak

Coordinate and bearing help

3 posts in this topic

#1 ·  Posted (edited)

I'm trying to determine my bearings by inputting a starting and destination coordinates but my bearings seem to be off by about 6 degrees. Can I get some help, is my math wrong?

Global $startLat = "40.730222780"
Global $startLong = "-73.996576310"
Global $endLat = "40.729377235"
Global $endLong = "-73.977298738"

$PI = 4 * ATan(1)

;===Turn coordinates into degrees.
$dLat = _Radian ( Number($endLat) - Number($startLat) )
$dLong = _Radian ( Number($endLong) - Number($startLong) )

;Check which quadrant the coordinate is in and find the degrees
If $dLong > 0 Then
    $Bearing = 90 - (180 / $PI) * Atan($dLat / $dLong)
EndIf
If $dLong < 0 Then
    $Bearing = 270 - (180 / $PI) * Atan($dLat / $dLong)
EndIf

If $dLong = 0 Then
    If $dLat > 0 Then $Bearing = 0
    If $dLat < 0 Then $Bearing = 180
    If $dLat = 0 Then Return
EndIf


$Bearing = Round($bearing)
MsgBox(0,0,$Bearing)

;$READTRUECOURSE = $GPSTK.TrueCourse

#cs
_ConsoleWrite("POI: " & $NAV_POI_ARRAY[$X][0] & ", " & $NAV_POI_ARRAY[$X][1])
_ConsoleWrite("Current: " & StringTrimRight($READLAT, 4) & ", " & StringtrimLeft(StringTrimRight($READLONG, 4),1))
_ConsoleWrite("Degrees: " & $Bearing & ", Direction = " & getCompassDirection($Bearing))
_ConsoleWrite("> Range: " & $Bearing - 15 & " and " & $Bearing + 15)
_ConsoleWrite("- True Course: " & $READTRUECOURSE)
#ce

I just don't know how anyone will be able to verify their results. But if it's clear what I did wrong, please let me know.

Thanks.

Edited by Champak

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Try:

$dLat = _Radian ( Abs (Number($endLat) - Number($startLat) ) )
$dLong = _Radian ( Abs (Number($endLong) - Number($startLong) ) )

Br,

UEZ


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Nope, that didn't fix it. It turns out the angle of approach and a few extra feet were making it seem like the bearing was off, but the original code seems to be working properly. Thanks anyway.

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