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GPS NMEA Parser in PHP. Tested on a Raspberry Pi with a GY-GPS6MU2.
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<?php | |
class GPS | |
{ | |
private $serialFile; | |
public function __construct($serialFile) | |
{ | |
$this->serialFile = $serialFile; | |
} | |
public function getFixData() | |
{ | |
$parts = $this->getLineParts('GGA'); | |
list($hour, $minute, $second) = str_split((string) $parts[0], 2); | |
return [ | |
'time' => $hour . ':' . $minute . ':' . $second, | |
'latitude' => $this->coordinatesToDecimal($parts[1], $parts[2]), | |
'longitude' => $this->coordinatesToDecimal($parts[3], $parts[4]), | |
'quality' => $this->getQuality((int) $parts[5]), | |
'satellites' => (int) $parts[6], | |
'altitude' => (int) $parts[8], | |
]; | |
} | |
private function coordinatesToDecimal($coordinate, $direction) | |
{ | |
$breakPoint = strpos($coordinate, '.') - 2; | |
$minutes = (float) substr($coordinate, $breakPoint); | |
$degrees = (int) substr($coordinate, 0, $breakPoint); | |
$decimal = $degrees + ($minutes / 60); | |
return in_array($direction, ['S', 'W']) ? -$decimal : $decimal; | |
} | |
private function getQuality($code) | |
{ | |
switch ($code) { | |
case 0: return 'invalid'; | |
case 1: return 'gps-fix'; | |
case 2: return 'dgps-fix'; | |
case 3: return 'pps-fix'; | |
case 4: return 'real-time-kinematic'; | |
case 5: return 'float-rtk'; | |
case 6: return 'estimated'; | |
case 7: return 'manual-input'; | |
case 8: return 'simulation'; | |
} | |
return 'unknown'; | |
} | |
private function getLineParts($type) | |
{ | |
$stream = fopen($this->serialFile, 'r'); | |
if (false === $stream) { | |
throw new RuntimeException('Could not open file for reading: ' . $serialFile); | |
} | |
$prefix = '$GP' . $type; | |
while (!feof($stream)) { | |
$line = fgets($stream); | |
if (strncmp($line, $prefix, strlen($prefix)) !== 0) { | |
continue; | |
} | |
$parts = explode(',', $line); | |
array_shift($parts); | |
fclose($stream); | |
return $parts; | |
} | |
fclose($stream); | |
throw new RuntimException('Could not find line type: ' . $type); | |
} | |
} |
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