A geo URI may be used to encode a point on the earth, including altitude. For example, to encode the Google's New York office, which is at 40.71872 deg N latitude, 73.98905 deg W longitude, at a point 100 meters above the office, one would encode "geo:40.71872,-73.98905,100".
A reader might open a local mapping application like Google Maps to this location and zoom accordingly, or could open a link to this location on a mapping web site like Google Maps in the device's web browser.
use Da\QrCode\QrCode;
use Da\QrCode\Format\GeoFormat;
$format = new GeoFormat(['lat' => 1,'lng' => 1, 'altitude' => 20]);
$qrCode = new QrCode($format);
header('Content-Type: ' . $qrCode->getContentType());
echo $qrCode->writeString();
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