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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 function assert; |
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use PHPCoord\UnitOfMeasure\Angle\ArcSecond; |
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use function round; |
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use SplFileObject; |
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use function unpack; |
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use function usort; |
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class NTv2Grid extends GeographicGrid |
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{ |
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private const RECORD_SIZE = 16; |
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private const FLAG_WITHIN_LIMITS = 1; |
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private const FLAG_ON_UPPER_LATITUDE = 2; |
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private const FLAG_ON_UPPER_LONGITUDE = 3; |
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private const FLAG_ON_UPPER_LATITUDE_AND_LONGITUDE = 4; |
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private string $integerFormatChar = 'V'; |
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private string $doubleFormatChar = 'e'; |
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private string $floatFormatChar = 'g'; |
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private array $subFileMetaData = []; |
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public function __construct($filename) |
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{ |
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$this->gridFile = new SplFileObject($filename); |
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$this->storageOrder = self::STORAGE_ORDER_INCREASING_LATITUDE_INCREASING_LONGITUDE; |
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$this->readHeader(); |
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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 $y): array |
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{ |
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// NTv2 is longitude positive *west* |
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$x *= -1; |
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// NTv2 is in seconds, not degrees |
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$x *= 3600; |
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$y *= 3600; |
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$gridToUse = $this->determineBestGrid($x, $y); |
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return $gridToUse->getValues($x, $y); |
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} |
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private function readHeader(): void |
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{ |
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$this->gridFile->fseek(0); |
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$rawData = $this->gridFile->fread(11 * self::RECORD_SIZE); |
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if (unpack('VNUM_OREC', $rawData, 8)['NUM_OREC'] !== 11) { |
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$this->integerFormatChar = 'N'; |
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$this->doubleFormatChar = 'E'; |
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$this->floatFormatChar = 'G'; |
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} |
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$data = unpack("A8/{$this->integerFormatChar}NUM_OREC/x4/A8/{$this->integerFormatChar}NUM_SREC/x4/A8/{$this->integerFormatChar}NUM_FILE/x4/A8/A8GS_TYPE/A8/A8VERSION/A8/A8SYSTEM_F/A8/A8SYSTEM_T/A8/{$this->doubleFormatChar}MAJOR_F/A8/{$this->doubleFormatChar}MINOR_F/A8/{$this->doubleFormatChar}MAJOR_T/A8/{$this->doubleFormatChar}MINOR_T", $rawData); |
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assert($data['GS_TYPE'] === 'SECONDS'); |
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$subFileStart = 11 * self::RECORD_SIZE; |
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for ($i = 0; $i < $data['NUM_FILE']; ++$i) { |
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$this->gridFile->fseek($subFileStart); |
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$subFileRawData = $this->gridFile->fread(11 * self::RECORD_SIZE); |
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$subFileData = unpack("A8/A8SUB_NAME/A8/A8PARENT/A8/A8CREATED/A8/A8UPDATED/A8/{$this->doubleFormatChar}S_LAT/A8/{$this->doubleFormatChar}N_LAT/A8/{$this->doubleFormatChar}E_LONG/A8/{$this->doubleFormatChar}W_LONG/A8/{$this->doubleFormatChar}LAT_INC/A8/{$this->doubleFormatChar}LONG_INC/A8/{$this->integerFormatChar}GS_COUNT/x4", $subFileRawData); |
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$subFileData['offsetStart'] = $subFileStart; |
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//apply rounding to eliminate fp issues when being deserialized |
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$subFileData['S_LAT'] = round($subFileData['S_LAT'], 5); |
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$subFileData['N_LAT'] = round($subFileData['N_LAT'], 5); |
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$subFileData['E_LONG'] = round($subFileData['E_LONG'], 5); |
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$subFileData['W_LONG'] = round($subFileData['W_LONG'], 5); |
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$this->subFileMetaData[$subFileData['SUB_NAME']] = $subFileData; |
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$subFileStart += 11 * self::RECORD_SIZE + $subFileData['GS_COUNT'] * self::RECORD_SIZE; |
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} |
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} |
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private function determineBestGrid(float $longitude, float $latitude): NTv2SubGrid |
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{ |
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$possibleGrids = []; |
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foreach ($this->subFileMetaData as $subFileMetaDatum) { |
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if ($latitude === $subFileMetaDatum['N_LAT'] && $longitude === $subFileMetaDatum['W_LONG']) { |
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$possibleGrids[] = [self::FLAG_ON_UPPER_LATITUDE_AND_LONGITUDE, $subFileMetaDatum]; |
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} elseif ($longitude === $subFileMetaDatum['W_LONG']) { |
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$possibleGrids[] = [self::FLAG_ON_UPPER_LONGITUDE, $subFileMetaDatum]; |
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} elseif ($latitude === $subFileMetaDatum['N_LAT']) { |
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$possibleGrids[] = [self::FLAG_ON_UPPER_LATITUDE, $subFileMetaDatum]; |
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} elseif ($latitude >= $subFileMetaDatum['S_LAT'] && $latitude <= $subFileMetaDatum['N_LAT'] && $longitude >= $subFileMetaDatum['E_LONG'] && $longitude <= $subFileMetaDatum['W_LONG']) { |
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$possibleGrids[] = [self::FLAG_WITHIN_LIMITS, $subFileMetaDatum]; |
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} |
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} |
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usort($possibleGrids, static function ($a, $b) { |
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return $a[0] <=> $b[0] ?: $a[1]['LAT_INC'] <=> $b[1]['LAT_INC'] ?: $a[2]['LONG_INC'] <=> $b[2]['LONG_INC']; |
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}); |
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$gridToUse = $possibleGrids[0][1]; |
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return new NTv2SubGrid( |
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$this->gridFile->getPathname(), |
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$gridToUse['offsetStart'], |
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$gridToUse['S_LAT'], |
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$gridToUse['N_LAT'], |
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$gridToUse['E_LONG'], |
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$gridToUse['W_LONG'], |
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$gridToUse['LAT_INC'], |
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$gridToUse['LONG_INC'], |
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$this->floatFormatChar |
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); |
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} |
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} |
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dvdoug /
PHPCoord
