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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 PHPCoord\UnitOfMeasure\Angle\ArcSecond; |
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use SplFileObject; |
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use function unpack; |
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class NTv2SubGrid extends Grid |
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{ |
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use BilinearInterpolation; |
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private const RECORD_SIZE = 16; |
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private int $offsetStart; |
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private string $floatFormatChar; |
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public function __construct( |
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string $filename, |
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int $offsetStart, |
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float $minLatitude, |
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float $maxLatitude, |
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float $minLongitude, |
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float $maxLongitude, |
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float $latitudeInterval, |
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float $longitudeInterval, |
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string $floatFormatChar |
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) { |
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$this->gridFile = new SplFileObject($filename); |
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$this->offsetStart = $offsetStart; |
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$this->startX = $minLongitude; |
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$this->endX = $maxLongitude; |
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$this->startY = $minLatitude; |
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$this->endY = $maxLatitude; |
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$this->columnGridInterval = $longitudeInterval; |
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$this->rowGridInterval = $latitudeInterval; |
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$this->floatFormatChar = $floatFormatChar; |
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$this->numberOfColumns = (int) (($this->endX - $this->startX) / $this->columnGridInterval); |
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$this->numberOfRows = (int) (($this->endY - $this->startY) / $this->rowGridInterval); |
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} |
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/** |
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* @return ArcSecond[] |
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*/ |
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public function getValues(float $x, float $y): array |
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{ |
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$shifts = $this->interpolate($x, $y); |
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return [new ArcSecond($shifts[0]), new ArcSecond(-$shifts[1])]; // NTv2 is longitude positive *west* |
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} |
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protected function getRecord(int $longitudeIndex, int $latitudeIndex): GridValues |
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{ |
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$recordIndex = $latitudeIndex * ($this->numberOfColumns + 1) + $longitudeIndex; |
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$recordOffset = $this->offsetStart + ((11 + $recordIndex) * self::RECORD_SIZE); |
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$this->gridFile->fseek($recordOffset); |
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$rawRecord = $this->gridFile->fread(self::RECORD_SIZE); |
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$shifts = unpack("{$this->floatFormatChar}LATITUDE_SHIFT/{$this->floatFormatChar}LONGITUDE_SHIFT/{$this->floatFormatChar}LATITUDE_ACCURACY/{$this->floatFormatChar}LONGITUDE_ACCURACY", $rawRecord); |
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return new GridValues( |
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$longitudeIndex * $this->columnGridInterval + $this->startX, |
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$latitudeIndex * $this->rowGridInterval + $this->startY, |
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[$shifts['LATITUDE_SHIFT'], $shifts['LONGITUDE_SHIFT']] |
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); |
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} |
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} |
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dvdoug /
PHPCoord
