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<?php |
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/** |
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* PHPCoord. |
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* |
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* @author Doug Wright |
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*/ |
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declare(strict_types=1); |
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namespace PHPCoord\CoordinateOperation; |
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use SplFileObject; |
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use UnexpectedValueException; |
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use function unpack; |
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class NADCON5Grid extends Grid |
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{ |
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use BiquadraticInterpolation; |
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private string $gridDataType; |
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public function __construct($filename) |
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{ |
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$this->gridFile = new SplFileObject($filename); |
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$header = $this->getHeader(); |
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$this->startX = $header['xlonsw']; |
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$this->startY = $header['xlatsw']; |
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$this->columnGridInterval = $header['dlon']; |
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$this->rowGridInterval = $header['dlat']; |
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$this->numberOfColumns = $header['nlon']; |
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$this->numberOfRows = $header['nlat']; |
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$this->gridDataType = match ($header['ikind']) { |
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1 => 'G', |
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default => throw new UnexpectedValueException("Unknown ikind: {$header['ikind']}"), |
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}; |
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} |
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protected function getRecord(int $longitudeIndex, int $latitudeIndex): GridValues |
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{ |
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$startBytes = 52; |
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$dataTypeBytes = $this->gridDataType === 'n' ? 2 : 4; |
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$recordLength = 4 + $this->numberOfColumns * $dataTypeBytes + 4; |
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$this->gridFile->fseek($startBytes + $recordLength * $latitudeIndex); |
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$rawRow = $this->gridFile->fread($recordLength); |
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$row = unpack("Gstartbuffer/{$this->gridDataType}{$this->numberOfColumns}lon/Gendbuffer", $rawRow); |
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return new GridValues( |
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$longitudeIndex * $this->columnGridInterval + $this->startX, |
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$latitudeIndex * $this->rowGridInterval + $this->startY, |
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[$row['lon' . ($longitudeIndex + 1)]] |
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); |
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} |
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private function getHeader(): array |
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{ |
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$this->gridFile->fseek(0); |
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$rawData = $this->gridFile->fread(52); |
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$data = unpack('Gstartbuffer/Exlatsw/Exlonsw/Edlat/Edlon/Nnlat/Nnlon/Nikind/Gendbuffer/', $rawData); |
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return $data; |
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} |
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public function getValues(float $x, float $y): array |
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{ |
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if ($x < 0) { |
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$x += 360; // NADCON5 uses 0 = 360 = Greenwich |
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} |
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return $this->interpolate($x, $y); |
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} |
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} |
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dvdoug /
PHPCoord
