Add kilometers to a map point

Question

Good morning.

I would like to know how do I add kilometers to a map point (latitude / longitude).

For example: The city Jaraguá do Sul is in latitude -26.462049, longitude -49.059448. I want to add 100 kilometers up, down, and on the sides. I want to do a square and get the new points.

How do I do that?

I tried it:

<?php
$distance = 100;
$earthRadius = 6371;
$lat1 = -26.4853239150483;
$lon1 = -49.075927734375;
$bearing = 0;

$lat2 = asin(sin($lat1) * cos($distance / $earthRadius) + cos($lat1) * sin($distance / $earthRadius) * cos($bearing));
$lon2 = $lon1 + atan2(sin($bearing) * sin($distance / $earthRadius) * cos($lat1), cos($distance / $earthRadius) - sin($lat1) * sin($lat2));

echo 'LAT: ' . $lat2 . '<br >';
echo 'LNG: ' . $lon2;
?>

But it's returning wrong cordinates. Thank you!

Thank you very much.

Answer 1

as was already pointed out. PHP trigonometric functions take radians as paramters.

degree to radian conversions of the parameters will do the trick. you probably want the result in degrees, so use rad2deg to convert back:

<?php
$distance = 100;
$earthRadius = 6371;
$lat1 = deg2rad(-26.4853239150483);
$lon1 = deg2rad(-49.075927734375);
$bearing = deg2rad(0);

$lat2 = asin(sin($lat1) * cos($distance / $earthRadius) + cos($lat1) * sin($distance / $earthRadius) * cos($bearing));
$lon2 = $lon1 + atan2(sin($bearing) * sin($distance / $earthRadius) * cos($lat1), cos($distance / $earthRadius) - sin($lat1) * sin($lat2));

echo 'LAT: ' . rad2deg($lat2) . '<br >';
echo 'LNG: ' . rad2deg($lon2);
?>